// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//
// This class represents the Default COM+ binder.
//
//
namespace System {

    using System;
    using System.Reflection;
    using System.Runtime.CompilerServices;
    using System.Runtime.Versioning;
    using System.Diagnostics.Contracts;
    using CultureInfo = System.Globalization.CultureInfo;
    //Marked serializable even though it has no state.
    [Serializable]
    internal class DefaultBinder : Binder
    {
        // This method is passed a set of methods and must choose the best
        // fit.  The methods all have the same number of arguments and the object
        // array args.  On exit, this method will choice the best fit method
        // and coerce the args to match that method.  By match, we mean all primitive
        // arguments are exact matchs and all object arguments are exact or subclasses
        // of the target.  If the target OR is an interface, the object must implement
        // that interface.  There are a couple of exceptions
        // thrown when a method cannot be returned.  If no method matchs the args and
        // ArgumentException is thrown.  If multiple methods match the args then 
        // an AmbiguousMatchException is thrown.
        // 
        // The most specific match will be selected.  
        // 
        [System.Security.SecuritySafeCritical]  // auto-generated
        public override MethodBase BindToMethod(
            BindingFlags bindingAttr, MethodBase[] match, ref Object[] args, 
            ParameterModifier[] modifiers, CultureInfo cultureInfo, String[] names, out Object state)
        {
            if (match == null || match.Length == 0)
                throw new ArgumentException(Environment.GetResourceString("Arg_EmptyArray"), "match");
            Contract.EndContractBlock();

            MethodBase[] candidates = (MethodBase[]) match.Clone();

            int i;
            int j;
        
            state = null;

            #region Map named parameters to candidate parameter postions
            // We are creating an paramOrder array to act as a mapping
            //  between the order of the args and the actual order of the
            //  parameters in the method.  This order may differ because
            //  named parameters (names) may change the order.  If names
            //  is not provided, then we assume the default mapping (0,1,...)
            int[][] paramOrder = new int[candidates.Length][];

            for (i = 0; i < candidates.Length; i++) 
            {
                ParameterInfo[] par = candidates[i].GetParametersNoCopy();

                // args.Length + 1 takes into account the possibility of a last paramArray that can be omitted
                paramOrder[i] = new int[(par.Length > args.Length) ? par.Length : args.Length];

                if (names == null) 
                {
                    // Default mapping
                    for (j = 0; j < args.Length; j++)
                        paramOrder[i][j] = j;
                }
                else 
                {
                    // Named parameters, reorder the mapping.  If CreateParamOrder fails, it means that the method
                    // doesn't have a name that matchs one of the named parameters so we don't consider it any further.
                     if (!CreateParamOrder(paramOrder[i], par, names))
                         candidates[i] = null;
                }               
            }
            #endregion

            Type[] paramArrayTypes = new Type[candidates.Length];
            
            Type[] argTypes = new Type[args.Length];

            #region Cache the type of the provided arguments
            // object that contain a null are treated as if they were typeless (but match either object 
            // references or value classes).  We mark this condition by placing a null in the argTypes array.
            for (i = 0; i < args.Length; i++) 
            {
                if (args[i] != null)
                {
                    argTypes[i] = args[i].GetType();
                }
            }
            #endregion

            
            // Find the method that matches...
            int CurIdx = 0;
            bool defaultValueBinding = ((bindingAttr & BindingFlags.OptionalParamBinding) != 0);

            Type paramArrayType = null;

            #region Filter methods by parameter count and type
            for (i = 0; i < candidates.Length; i++) 
            {
                paramArrayType = null;

                // If we have named parameters then we may have a hole in the candidates array.
                if (candidates[i] == null)
                    continue;
                
                // Validate the parameters.
                ParameterInfo[] par = candidates[i].GetParametersNoCopy();

                #region Match method by parameter count
                if (par.Length == 0) 
                {
                    #region No formal parameters
                    if (args.Length != 0)
                    {
                        if ((candidates[i].CallingConvention & CallingConventions.VarArgs) == 0) 
                            continue;
                    }

                    // This is a valid routine so we move it up the candidates list.
                    paramOrder[CurIdx] = paramOrder[i];
                    candidates[CurIdx++] = candidates[i];

                    continue;
                    #endregion
                }
                else if (par.Length > args.Length) 
                {
                    #region Shortage of provided parameters
                    // If the number of parameters is greater than the number of args then 
                    // we are in the situation were we may be using default values.
                    for (j = args.Length; j < par.Length - 1; j++) 
                    {
                        if (par[j].DefaultValue == System.DBNull.Value)
                           break;
                    }

                    if (j != par.Length - 1)
                        continue;       

                    if (par[j].DefaultValue == System.DBNull.Value) 
                    {
                        if (!par[j].ParameterType.IsArray) 
                            continue;

                        if (!par[j].IsDefined(typeof(ParamArrayAttribute), true)) 
                            continue;

                        paramArrayType = par[j].ParameterType.GetElementType();
                    }
                    #endregion
                }
                else if (par.Length < args.Length) 
                {
                    #region Excess provided parameters
                    // test for the ParamArray case
                    int lastArgPos = par.Length - 1;

                    if (!par[lastArgPos].ParameterType.IsArray) 
                        continue;

                    if (!par[lastArgPos].IsDefined(typeof(ParamArrayAttribute), true)) 
                        continue;

                    if (paramOrder[i][lastArgPos] != lastArgPos)
                        continue; 

                    paramArrayType = par[lastArgPos].ParameterType.GetElementType();
                    #endregion
                }
                else 
                {
                    #region Test for paramArray, save paramArray type
                    int lastArgPos = par.Length - 1;

                    if (par[lastArgPos].ParameterType.IsArray
                        && par[lastArgPos].IsDefined(typeof(ParamArrayAttribute), true)
                        && paramOrder[i][lastArgPos] == lastArgPos)
                    {
                        if (!par[lastArgPos].ParameterType.IsAssignableFrom(argTypes[lastArgPos]))
                            paramArrayType = par[lastArgPos].ParameterType.GetElementType();
                    }
                    #endregion
                }
                #endregion

                Type pCls = null;
                int argsToCheck = (paramArrayType != null) ? par.Length - 1 : args.Length;

                #region Match method by parameter type
                for (j = 0; j < argsToCheck; j++) 
                {
                    #region Classic argument coersion checks
                    // get the formal type
                    pCls = par[j].ParameterType;

                    if (pCls.IsByRef)
                        pCls = pCls.GetElementType();

                    // the type is the same
                    if (pCls == argTypes[paramOrder[i][j]])
                        continue;

                    // a default value is available
                    if (defaultValueBinding && args[paramOrder[i][j]] == Type.Missing)
                        continue;   

                    // the argument was null, so it matches with everything
                    if (args[paramOrder[i][j]] == null)
                        continue;

                    // the type is Object, so it will match everything
                    if (pCls == typeof(Object))
                        continue;

                    // now do a "classic" type check
                    if (pCls.IsPrimitive) 
                    {
                        if (argTypes[paramOrder[i][j]] == null || !CanConvertPrimitiveObjectToType(args[paramOrder[i][j]],(RuntimeType)pCls)) 
                        {
                            break;
                        }
                    }
                    else 
                    {
                        if (argTypes[paramOrder[i][j]] == null)
                            continue;

                        if (!pCls.IsAssignableFrom(argTypes[paramOrder[i][j]])) 
                        {
                            if (argTypes[paramOrder[i][j]].IsCOMObject) 
                            {
                                if (pCls.IsInstanceOfType(args[paramOrder[i][j]]))
                                    continue;
                            }
                            break;
                        }
                    }
                    #endregion
                }

                if (paramArrayType != null && j == par.Length - 1) 
                {
                    #region Check that excess arguments can be placed in the param array
                    for (; j < args.Length; j++) 
                    {
                        if (paramArrayType.IsPrimitive) 
                        {
                            if (argTypes[j] == null || !CanConvertPrimitiveObjectToType(args[j], (RuntimeType)paramArrayType))
                                break;
                        }
                        else 
                        {
                            if (argTypes[j] == null)
                                continue;

                            if (!paramArrayType.IsAssignableFrom(argTypes[j])) 
                            {
                                if (argTypes[j].IsCOMObject) 
                                {
                                    if (paramArrayType.IsInstanceOfType(args[j]))
                                        continue;
                                }

                                break;
                            }
                        }
                    }
                    #endregion
                }
                #endregion

                if (j == args.Length) 
                {
                    #region This is a valid routine so we move it up the candidates list
                    paramOrder[CurIdx] = paramOrder[i];
                    paramArrayTypes[CurIdx] = paramArrayType;
                    candidates[CurIdx++] = candidates[i];
                    #endregion
                }
            }
            #endregion

            // If we didn't find a method 
            if (CurIdx == 0)
                throw new MissingMethodException(Environment.GetResourceString("MissingMember"));

            if (CurIdx == 1) 
            {
                #region Found only one method
                if (names != null) 
                {
                    state = new BinderState((int[])paramOrder[0].Clone(), args.Length, paramArrayTypes[0] != null);
                    ReorderParams(paramOrder[0],args);
                }
                
                // If the parameters and the args are not the same length or there is a paramArray
                //  then we need to create a argument array.
                ParameterInfo[] parms = candidates[0].GetParametersNoCopy();              

                if (parms.Length == args.Length) 
                {
                    if (paramArrayTypes[0] != null) 
                    {
                        Object[] objs = new Object[parms.Length];
                        int lastPos = parms.Length - 1;
                        Array.Copy(args, 0, objs, 0, lastPos);
                        objs[lastPos] = Array.UnsafeCreateInstance(paramArrayTypes[0], 1); 
                        ((Array)objs[lastPos]).SetValue(args[lastPos], 0);
                        args = objs;
                    }
                }
                else if (parms.Length > args.Length) 
                {
                    Object[] objs = new Object[parms.Length];

                    for (i=0;i<args.Length;i++)
                        objs[i] = args[i];

                    for (;i<parms.Length - 1;i++)
                        objs[i] = parms[i].DefaultValue;

                    if (paramArrayTypes[0] != null)
                        objs[i] = Array.UnsafeCreateInstance(paramArrayTypes[0], 0); // create an empty array for the 

                    else
                        objs[i] = parms[i].DefaultValue;

                    args = objs;
                }
                else 
                {
                    if ((candidates[0].CallingConvention & CallingConventions.VarArgs) == 0) 
                    {
                        Object[] objs = new Object[parms.Length];
                        int paramArrayPos = parms.Length - 1;
                        Array.Copy(args, 0, objs, 0, paramArrayPos);
                        objs[paramArrayPos] = Array.UnsafeCreateInstance(paramArrayTypes[0], args.Length - paramArrayPos); 
                        Array.Copy(args, paramArrayPos, (System.Array)objs[paramArrayPos], 0, args.Length - paramArrayPos);
                        args = objs;
                    }
                }
                #endregion

                return candidates[0];
            }
            
            int currentMin = 0;
            bool ambig = false;
            for (i = 1; i < CurIdx; i++) 
            {
                #region Walk all of the methods looking the most specific method to invoke
                int newMin = FindMostSpecificMethod(candidates[currentMin], paramOrder[currentMin], paramArrayTypes[currentMin],
                                                    candidates[i], paramOrder[i], paramArrayTypes[i], argTypes, args);

                if (newMin == 0)
                {
                    ambig = true;
                }
                else  if (newMin == 2) 
                {
                    currentMin = i;
                    ambig = false;
                }
                #endregion
            }

            if (ambig)
                throw new AmbiguousMatchException(Environment.GetResourceString("Arg_AmbiguousMatchException"));

            // Reorder (if needed)
            if (names != null) {
                state = new BinderState((int[])paramOrder[currentMin].Clone(), args.Length, paramArrayTypes[currentMin] != null);
                ReorderParams(paramOrder[currentMin], args);
            }
                
            // If the parameters and the args are not the same length or there is a paramArray
            //  then we need to create a argument array.
            ParameterInfo[] parameters = candidates[currentMin].GetParametersNoCopy();
            if (parameters.Length == args.Length) 
            {
                if (paramArrayTypes[currentMin] != null) 
                {
                    Object[] objs = new Object[parameters.Length];
                    int lastPos = parameters.Length - 1;
                    Array.Copy(args, 0, objs, 0, lastPos);
                    objs[lastPos] = Array.UnsafeCreateInstance(paramArrayTypes[currentMin], 1); 
                    ((Array)objs[lastPos]).SetValue(args[lastPos], 0);
                    args = objs;
                }
            }
            else if (parameters.Length > args.Length) 
            {
                Object[] objs = new Object[parameters.Length];

                for (i=0;i<args.Length;i++)
                    objs[i] = args[i];

                for (;i<parameters.Length - 1;i++)
                    objs[i] = parameters[i].DefaultValue;

                if (paramArrayTypes[currentMin] != null) 
                {
                    objs[i] = Array.UnsafeCreateInstance(paramArrayTypes[currentMin], 0);
                }
                else
                {
                    objs[i] = parameters[i].DefaultValue;
                }

                args = objs;
            }
            else 
            {
                if ((candidates[currentMin].CallingConvention & CallingConventions.VarArgs) == 0) 
                {
                    Object[] objs = new Object[parameters.Length];
                    int paramArrayPos = parameters.Length - 1;
                    Array.Copy(args, 0, objs, 0, paramArrayPos);
                    objs[paramArrayPos] = Array.UnsafeCreateInstance(paramArrayTypes[currentMin], args.Length - paramArrayPos);
                    Array.Copy(args, paramArrayPos, (System.Array)objs[paramArrayPos], 0, args.Length - paramArrayPos);
                    args = objs;
                }
            }

            return candidates[currentMin];
        }
    
        
        // Given a set of fields that match the base criteria, select a field.
        // if value is null then we have no way to select a field
        [System.Security.SecuritySafeCritical]  // auto-generated
        public override FieldInfo BindToField(BindingFlags bindingAttr,FieldInfo[] match, Object value,CultureInfo cultureInfo)
        {
            if (match == null) {
                throw new ArgumentNullException("match");
            }

            int i;
            // Find the method that match...
            int CurIdx = 0;

            Type valueType = null;

            FieldInfo[] candidates = (FieldInfo[]) match.Clone();
            
            // If we are a FieldSet, then use the value's type to disambiguate
            if ((bindingAttr & BindingFlags.SetField) != 0) {
                valueType = value.GetType();
                
                for (i=0;i<candidates.Length;i++) {
                    Type pCls = candidates[i].FieldType;
                    if (pCls == valueType) {
                        candidates[CurIdx++] = candidates[i];
                        continue;
                    }
                    if (value == Empty.Value) {
                        // the object passed in was null which would match any non primitive non value type
                        if (pCls.IsClass) {
                            candidates[CurIdx++] = candidates[i];
                            continue;
                        }
                    }
                    if (pCls == typeof(Object)) {
                        candidates[CurIdx++] = candidates[i];
                        continue;
                    }
                    if (pCls.IsPrimitive) {
                        if (CanConvertPrimitiveObjectToType(value,(RuntimeType)pCls)) {
                            candidates[CurIdx++] = candidates[i];
                            continue;
                        }
                    }
                    else {
                        if (pCls.IsAssignableFrom(valueType)) {
                            candidates[CurIdx++] = candidates[i];
                            continue;
                        }
                    }
                }
                if (CurIdx == 0)
                    throw new MissingFieldException(Environment.GetResourceString("MissingField"));
                if (CurIdx == 1)
                    return candidates[0];
            }
            
            // Walk all of the methods looking the most specific method to invoke
            int currentMin = 0;
            bool ambig = false;
            for (i=1;i<CurIdx;i++) {
                int newMin = FindMostSpecificField(candidates[currentMin], candidates[i]);
                if (newMin == 0)
                    ambig = true;
                else {
                    if (newMin == 2) {
                        currentMin = i;
                        ambig = false;
                    }
                }
            }
            if (ambig)
                throw new AmbiguousMatchException(Environment.GetResourceString("Arg_AmbiguousMatchException"));
            return candidates[currentMin];
        }
        
        // Given a set of methods that match the base criteria, select a method based
        // upon an array of types.  This method should return null if no method matchs
        // the criteria.
        [System.Security.SecuritySafeCritical]  // auto-generated
        public override MethodBase SelectMethod(BindingFlags bindingAttr,MethodBase[] match,Type[] types,ParameterModifier[] modifiers)
        {
            int i;
            int j;
            
            Type[] realTypes = new Type[types.Length];
            for (i=0;i<types.Length;i++) {
                realTypes[i] = types[i].UnderlyingSystemType;
                if (!(realTypes[i] is RuntimeType))
                    throw new ArgumentException(Environment.GetResourceString("Arg_MustBeType"),"types");
            }
            types = realTypes;
            
            // We don't automatically jump out on exact match.
            if (match == null || match.Length == 0)
                throw new ArgumentException(Environment.GetResourceString("Arg_EmptyArray"), "match");

            MethodBase[] candidates = (MethodBase[]) match.Clone();
            
            // Find all the methods that can be described by the types parameter. 
            //  Remove all of them that cannot.
            int CurIdx = 0;
            for (i=0;i<candidates.Length;i++) {
                ParameterInfo[] par = candidates[i].GetParametersNoCopy();
                if (par.Length != types.Length)
                    continue;
                for (j=0;j<types.Length;j++) {
                    Type pCls = par[j].ParameterType;
                    if (pCls == types[j])
                        continue;
                    if (pCls == typeof(Object))
                        continue;
                    if (pCls.IsPrimitive) {
                        if (!(types[j].UnderlyingSystemType is RuntimeType) ||
                            !CanConvertPrimitive((RuntimeType)types[j].UnderlyingSystemType,(RuntimeType)pCls.UnderlyingSystemType))
                            break;
                    }
                    else {
                        if (!pCls.IsAssignableFrom(types[j]))
                            break;
                    }
                }
                if (j == types.Length)
                    candidates[CurIdx++] = candidates[i];
            }
            if (CurIdx == 0)
                return null;
            if (CurIdx == 1)
                return candidates[0];
            
            // Walk all of the methods looking the most specific method to invoke
            int currentMin = 0;
            bool ambig = false;
            int[] paramOrder = new int[types.Length];
            for (i=0;i<types.Length;i++)
                paramOrder[i] = i;
            for (i=1;i<CurIdx;i++) {
                int newMin = FindMostSpecificMethod(candidates[currentMin], paramOrder, null, candidates[i], paramOrder, null, types, null);
                if (newMin == 0)
                    ambig = true;
                else {
                    if (newMin == 2) {
                        currentMin = i;
                        ambig = false;
                        currentMin = i;
                    }
                }
            }
            if (ambig)
                throw new AmbiguousMatchException(Environment.GetResourceString("Arg_AmbiguousMatchException"));
            return candidates[currentMin];
        }
        
        // Given a set of properties that match the base criteria, select one.
        [System.Security.SecuritySafeCritical]  // auto-generated
        public override PropertyInfo SelectProperty(BindingFlags bindingAttr,PropertyInfo[] match,Type returnType,
                    Type[] indexes,ParameterModifier[] modifiers)
        {
            // Allow a null indexes array. But if it is not null, every element must be non-null as well.
            if (indexes != null && !Contract.ForAll(indexes, delegate(Type t) { return t != null; }))
            {
                throw new ArgumentNullException("indexes");
            }
            if (match == null || match.Length == 0)
                throw new ArgumentException(Environment.GetResourceString("Arg_EmptyArray"), "match");
            Contract.EndContractBlock();

            PropertyInfo[] candidates = (PropertyInfo[]) match.Clone();

            int i,j = 0;
                
            // Find all the properties that can be described by type indexes parameter
            int CurIdx = 0;
            int indexesLength = (indexes != null) ? indexes.Length : 0;
            for (i=0;i<candidates.Length;i++) {

                if (indexes != null)
                {
                    ParameterInfo[] par = candidates[i].GetIndexParameters();
                    if (par.Length != indexesLength)
                        continue;
                        
                    for (j=0;j<indexesLength;j++) {
                        Type pCls = par[j]. ParameterType;
                        
                        // If the classes  exactly match continue
                        if (pCls == indexes[j])
                            continue;
                        if (pCls == typeof(Object))
                            continue;
                        
                        if (pCls.IsPrimitive) {
                            if (!(indexes[j].UnderlyingSystemType is RuntimeType) ||
                                !CanConvertPrimitive((RuntimeType)indexes[j].UnderlyingSystemType,(RuntimeType)pCls.UnderlyingSystemType))
                                break;
                        }
                        else {
                            if (!pCls.IsAssignableFrom(indexes[j]))
                                break;
                        }
                    }
                }
                
                if (j == indexesLength) {
                    if (returnType != null) {
                        if (candidates[i].PropertyType.IsPrimitive) {
                            if (!(returnType.UnderlyingSystemType is RuntimeType) ||
                                !CanConvertPrimitive((RuntimeType)returnType.UnderlyingSystemType,(RuntimeType)candidates[i].PropertyType.UnderlyingSystemType))
                                continue;
                        }
                        else {
                            if (!candidates[i].PropertyType.IsAssignableFrom(returnType))
                                continue;
                        }
                    }
                    candidates[CurIdx++] = candidates[i];
                }
            }
            if (CurIdx == 0)
                return null;
            if (CurIdx == 1)
                return candidates[0];
                
            // Walk all of the properties looking the most specific method to invoke
            int currentMin = 0;
            bool ambig = false;
            int[] paramOrder = new int[indexesLength];
            for (i=0;i<indexesLength;i++)
                paramOrder[i] = i;
            for (i=1;i<CurIdx;i++) {
                int newMin = FindMostSpecificType(candidates[currentMin].PropertyType, candidates[i].PropertyType,returnType);
                if (newMin == 0 && indexes != null)
                    newMin = FindMostSpecific(candidates[currentMin].GetIndexParameters(),
                                              paramOrder,
                                              null,
                                              candidates[i].GetIndexParameters(),
                                              paramOrder,
                                              null,
                                              indexes, 
                                              null);
                if (newMin == 0)
                {
                    newMin = FindMostSpecificProperty(candidates[currentMin], candidates[i]);
                    if (newMin == 0)
                        ambig = true;
                }
                if (newMin == 2) {
                    ambig = false;
                    currentMin = i;
                }
            }

            if (ambig)
                throw new AmbiguousMatchException(Environment.GetResourceString("Arg_AmbiguousMatchException"));
            return candidates[currentMin];
        }
        
        // ChangeType
        // The default binder doesn't support any change type functionality.
        // This is because the default is built into the low level invoke code.
        public override Object ChangeType(Object value,Type type,CultureInfo cultureInfo)
        {
            throw new NotSupportedException(Environment.GetResourceString("NotSupported_ChangeType"));
        }
        
        public override void ReorderArgumentArray(ref Object[] args, Object state)
        {
            BinderState binderState = (BinderState)state;
            ReorderParams(binderState.m_argsMap, args);
            if (binderState.m_isParamArray) {
                int paramArrayPos = args.Length - 1;
                if (args.Length == binderState.m_originalSize)
                    args[paramArrayPos] = ((Object[])args[paramArrayPos])[0];
                else {
                    // must be args.Length < state.originalSize
                    Object[] newArgs = new Object[args.Length];
                    Array.Copy(args, 0, newArgs, 0, paramArrayPos);
                    for (int i = paramArrayPos, j = 0; i < newArgs.Length; i++, j++) {
                        newArgs[i] = ((Object[])args[paramArrayPos])[j];
                    }
                    args = newArgs;
                }
            }
            else {
                if (args.Length > binderState.m_originalSize) {
                    Object[] newArgs = new Object[binderState.m_originalSize];
                    Array.Copy(args, 0, newArgs, 0, binderState.m_originalSize);
                    args = newArgs;
                }
            }
        }

        // Return any exact bindings that may exist. (This method is not defined on the
        //  Binder and is used by RuntimeType.)
        public static MethodBase ExactBinding(MethodBase[] match,Type[] types,ParameterModifier[] modifiers)
        {
            if (match==null)
                throw new ArgumentNullException("match");
            Contract.EndContractBlock();
            MethodBase[] aExactMatches = new MethodBase[match.Length];
            int cExactMatches = 0;

            for (int i=0;i<match.Length;i++) {
                ParameterInfo[] par = match[i].GetParametersNoCopy();
                if (par.Length == 0) {
                    continue;
                }
                int j;
                for (j=0;j<types.Length;j++) {
                    Type pCls = par[j]. ParameterType;
                    
                    // If the classes  exactly match continue
                    if (!pCls.Equals(types[j]))
                        break;
                }
                if (j < types.Length)
                    continue;

                // Add the exact match to the array of exact matches.
                aExactMatches[cExactMatches] = match[i];
                cExactMatches++;
            }

            if (cExactMatches == 0)
                return null;

            if (cExactMatches == 1)
                return aExactMatches[0];

            return FindMostDerivedNewSlotMeth(aExactMatches, cExactMatches);
        }
        
        // Return any exact bindings that may exist. (This method is not defined on the
        //  Binder and is used by RuntimeType.)
        public static PropertyInfo ExactPropertyBinding(PropertyInfo[] match,Type returnType,Type[] types,ParameterModifier[] modifiers)
        {
            if (match==null)
                throw new ArgumentNullException("match");
            Contract.EndContractBlock();

            PropertyInfo bestMatch = null;
            int typesLength = (types != null) ? types.Length : 0;
            for (int i=0;i<match.Length;i++) {
                ParameterInfo[] par = match[i].GetIndexParameters();
                int j;
                for (j=0;j<typesLength;j++) {
                    Type pCls = par[j].ParameterType;
                    
                    // If the classes  exactly match continue
                    if (pCls != types[j])
                        break;
                }
                if (j < typesLength)
                    continue;
                if (returnType != null && returnType != match[i].PropertyType)
                    continue;
                
                if (bestMatch != null)
                    throw new AmbiguousMatchException(Environment.GetResourceString("Arg_AmbiguousMatchException"));

                bestMatch = match[i];
            }
            return bestMatch;
        }

        private static int FindMostSpecific(ParameterInfo[] p1, int[] paramOrder1, Type paramArrayType1,
                                            ParameterInfo[] p2, int[] paramOrder2, Type paramArrayType2,
                                            Type[] types, Object[] args)
        {
            // A method using params is always less specific than one not using params
            if (paramArrayType1 != null && paramArrayType2 == null) return 2;
            if (paramArrayType2 != null && paramArrayType1 == null) return 1;

            // now either p1 and p2 both use params or neither does.

            bool p1Less = false;
            bool p2Less = false;

            for (int i = 0; i < types.Length; i++)
            {
                if (args != null && args[i] == Type.Missing)
                    continue;

                Type c1, c2;

                //  If a param array is present, then either
                //      the user re-ordered the parameters in which case
                //          the argument to the param array is either an array
                //              in which case the params is conceptually ignored and so paramArrayType1 == null
                //          or the argument to the param array is a single element
                //              in which case paramOrder[i] == p1.Length - 1 for that element
                //      or the user did not re-order the parameters in which case
                //          the paramOrder array could contain indexes larger than p.Length - 1 (see VSW 577286)
                //          so any index >= p.Length - 1 is being put in the param array

                if (paramArrayType1 != null && paramOrder1[i] >= p1.Length - 1)
                    c1 = paramArrayType1;
                else
                    c1 = p1[paramOrder1[i]].ParameterType;

                if (paramArrayType2 != null && paramOrder2[i] >= p2.Length - 1)
                    c2 = paramArrayType2;
                else
                    c2 = p2[paramOrder2[i]].ParameterType;

                if (c1 == c2) continue;

                switch (FindMostSpecificType(c1, c2, types[i])) {
                    case 0: return 0;
                    case 1: p1Less = true; break;
                    case 2: p2Less = true; break;
                }
            }

            // Two way p1Less and p2Less can be equal.  All the arguments are the
            //  same they both equal false, otherwise there were things that both
            //  were the most specific type on....
            if (p1Less == p2Less)
            {
                // if we cannot tell which is a better match based on parameter types (p1Less == p2Less),
                // let's see which one has the most matches without using the params array (the longer one wins).
                if (!p1Less && args != null)
                {
                    if (p1.Length > p2.Length)
                    {
                        return 1;
                    }
                    else if (p2.Length > p1.Length)
                    {
                        return 2;
                    }
                }

                return 0;
            }
            else
            {
                return (p1Less == true) ? 1 : 2;
            }
        }
        
        [System.Security.SecuritySafeCritical]  // auto-generated
        private static int FindMostSpecificType(Type c1, Type c2, Type t)
        {
            // If the two types are exact move on...
            if (c1 == c2)
                return 0;

            if (c1 == t) 
                return 1;
            
            if (c2 == t) 
                return 2;         

            bool c1FromC2;
            bool c2FromC1;

            if (c1.IsByRef || c2.IsByRef)
            {
                if (c1.IsByRef && c2.IsByRef)
                {
                    c1 = c1.GetElementType();
                    c2 = c2.GetElementType();
                }
                else if (c1.IsByRef)
                {
                    if (c1.GetElementType() == c2)
                        return 2;

                    c1 = c1.GetElementType();
                }
                else 
                {
                    if (c2.GetElementType() == c1)
                        return 1;

                    c2 = c2.GetElementType();
                }
            }
            

            if (c1.IsPrimitive && c2.IsPrimitive) 
            {
                c1FromC2 = CanConvertPrimitive((RuntimeType)c2, (RuntimeType)c1);
                c2FromC1 = CanConvertPrimitive((RuntimeType)c1, (RuntimeType)c2);
            }
            else
            {
                c1FromC2 = c1.IsAssignableFrom(c2);
                c2FromC1 = c2.IsAssignableFrom(c1);
            }

            if (c1FromC2 == c2FromC1)
                return 0;

            if (c1FromC2)
            {
                return 2;
            }
            else
            {
                return 1;
            }
        }

        private static int FindMostSpecificMethod(MethodBase m1, int[] paramOrder1, Type paramArrayType1,
                                                  MethodBase m2, int[] paramOrder2, Type paramArrayType2,
                                                  Type[] types, Object[] args)
        {
            // Find the most specific method based on the parameters.
            int res = FindMostSpecific(m1.GetParametersNoCopy(), paramOrder1, paramArrayType1,
                                       m2.GetParametersNoCopy(), paramOrder2, paramArrayType2, types, args);            

            // If the match was not ambigous then return the result.
            if (res != 0)
                return res;

            // Check to see if the methods have the exact same name and signature.
            if (CompareMethodSigAndName(m1, m2))
            {
                // Determine the depth of the declaring types for both methods.
                int hierarchyDepth1 = GetHierarchyDepth(m1.DeclaringType);
                int hierarchyDepth2 = GetHierarchyDepth(m2.DeclaringType);

                // The most derived method is the most specific one.
                if (hierarchyDepth1 == hierarchyDepth2) 
                {
                    return 0; 
                }
                else if (hierarchyDepth1 < hierarchyDepth2) 
                {
                    return 2;
                }
                else
                {
                    return 1;
                }
            }

            // The match is ambigous.
            return 0;
        }

        private static int FindMostSpecificField(FieldInfo cur1,FieldInfo cur2)
        {
            // Check to see if the fields have the same name.
            if (cur1.Name == cur2.Name)
            {
                int hierarchyDepth1 = GetHierarchyDepth(cur1.DeclaringType);
                int hierarchyDepth2 = GetHierarchyDepth(cur2.DeclaringType);

                if (hierarchyDepth1 == hierarchyDepth2) {
                    Contract.Assert(cur1.IsStatic != cur2.IsStatic, "hierarchyDepth1 == hierarchyDepth2");
                    return 0; 
                }
                else if (hierarchyDepth1 < hierarchyDepth2) 
                    return 2;
                else
                    return 1;
            }

            // The match is ambigous.
            return 0;
        }

        private static int FindMostSpecificProperty(PropertyInfo cur1,PropertyInfo cur2)
        {
            // Check to see if the fields have the same name.
            if (cur1.Name == cur2.Name)
            {
                int hierarchyDepth1 = GetHierarchyDepth(cur1.DeclaringType);
                int hierarchyDepth2 = GetHierarchyDepth(cur2.DeclaringType);

                if (hierarchyDepth1 == hierarchyDepth2) {
                    return 0; 
                }
                else if (hierarchyDepth1 < hierarchyDepth2) 
                    return 2;
                else
                    return 1;
            }

            // The match is ambigous.
            return 0;
        }
        
        internal static bool CompareMethodSigAndName(MethodBase m1, MethodBase m2)
        {
            ParameterInfo[] params1 = m1.GetParametersNoCopy();
            ParameterInfo[] params2 = m2.GetParametersNoCopy();

            if (params1.Length != params2.Length)
                return false;

            int numParams = params1.Length;
            for (int i = 0; i < numParams; i++)
            {
                if (params1[i].ParameterType != params2[i].ParameterType)
                    return false;
            }

            return true;
        }

        internal static int GetHierarchyDepth(Type t)
        {
            int depth = 0;

            Type currentType = t;
            do 
            {
                depth++;
                currentType = currentType.BaseType;
            } while (currentType != null);

            return depth;
        }

        internal static MethodBase FindMostDerivedNewSlotMeth(MethodBase[] match, int cMatches)
        {
            int deepestHierarchy = 0;
            MethodBase methWithDeepestHierarchy = null;

            for (int i = 0; i < cMatches; i++)
            {
                // Calculate the depth of the hierarchy of the declaring type of the
                // current method.
                int currentHierarchyDepth = GetHierarchyDepth(match[i].DeclaringType);

                // The two methods have the same name, signature, and hierarchy depth.
                // This can only happen if at least one is vararg or generic.
                if (currentHierarchyDepth == deepestHierarchy)
                {
                    throw new AmbiguousMatchException(Environment.GetResourceString("Arg_AmbiguousMatchException"));
                }

                // Check to see if this method is on the most derived class.
                if (currentHierarchyDepth > deepestHierarchy)
                {
                    deepestHierarchy = currentHierarchyDepth;
                    methWithDeepestHierarchy = match[i];
                }
            }

            return methWithDeepestHierarchy;
        }

        // CanConvertPrimitive
        // This will determine if the source can be converted to the target type
        [System.Security.SecurityCritical]  // auto-generated
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern bool CanConvertPrimitive(RuntimeType source,RuntimeType target);

        // CanConvertPrimitiveObjectToType
        // This method will determine if the primitive object can be converted
        //  to a type.
        [System.Security.SecurityCritical]  // auto-generated
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        static internal extern bool CanConvertPrimitiveObjectToType(Object source,RuntimeType type);
        
        // This method will sort the vars array into the mapping order stored
        //  in the paramOrder array.
        private static void ReorderParams(int[] paramOrder,Object[] vars)
        {
            object[] varsCopy = new object[vars.Length];
            for (int i = 0; i < vars.Length; i ++)
                varsCopy[i] = vars[i];
                    
            for (int i = 0; i < vars.Length; i ++)
                vars[i] = varsCopy[paramOrder[i]];
        }
        
        // This method will create the mapping between the Parameters and the underlying
        //  data based upon the names array.  The names array is stored in the same order
        //  as the values and maps to the parameters of the method.  We store the mapping
        //  from the parameters to the names in the paramOrder array.  All parameters that
        //  don't have matching names are then stored in the array in order.
        private static bool CreateParamOrder(int[] paramOrder,ParameterInfo[] pars,String[] names)
        {
            bool[] used = new bool[pars.Length];
            
            // Mark which parameters have not been found in the names list
            for (int i=0;i<pars.Length;i++)
                paramOrder[i] = -1;
            // Find the parameters with names. 
            for (int i=0;i<names.Length;i++) {
                int j;
                for (j=0;j<pars.Length;j++) {
                    if (names[i].Equals(pars[j].Name)) {
                        paramOrder[j] = i;
                        used[i] = true;
                        break;
                    }
                }
                // This is an error condition.  The name was not found.  This
                //  method must not match what we sent.
                if (j == pars.Length)
                    return false;
            }
            
            // Now we fill in the holes with the parameters that are unused.
            int pos = 0;
            for (int i=0;i<pars.Length;i++) {
                if (paramOrder[i] == -1) {
                    for (;pos<pars.Length;pos++) {
                        if (!used[pos]) {
                            paramOrder[i] = pos;
                            pos++;
                            break;
                        }
                    }
                }
            }
            return true;
        }

        internal class BinderState {
          internal int[] m_argsMap;
          internal int m_originalSize;
          internal bool m_isParamArray;

          internal BinderState(int[] argsMap, int originalSize, bool isParamArray) {
              m_argsMap = argsMap;
              m_originalSize = originalSize;
              m_isParamArray = isParamArray;
          }

        }

    }
}