path: root/src/mscorlib/src/System/Collections/SortedList.cs

// 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.

/*============================================================
**
**
** 
**
** Purpose: A sorted dictionary.
**
** 
===========================================================*/
namespace System.Collections {
    using System;
    using System.Security.Permissions;
    using System.Diagnostics;
    using System.Diagnostics.CodeAnalysis;
    using System.Diagnostics.Contracts;
    using System.Globalization;

    // The SortedList class implements a sorted list of keys and values. Entries in
    // a sorted list are sorted by their keys and are accessible both by key and by
    // index. The keys of a sorted list can be ordered either according to a
    // specific IComparer implementation given when the sorted list is
    // instantiated, or according to the IComparable implementation provided
    // by the keys themselves. In either case, a sorted list does not allow entries
    // with duplicate keys.
    // 
    // A sorted list internally maintains two arrays that store the keys and
    // values of the entries. The capacity of a sorted list is the allocated
    // length of these internal arrays. As elements are added to a sorted list, the
    // capacity of the sorted list is automatically increased as required by
    // reallocating the internal arrays.  The capacity is never automatically 
    // decreased, but users can call either TrimToSize or 
    // Capacity explicitly.
    // 
    // The GetKeyList and GetValueList methods of a sorted list
    // provides access to the keys and values of the sorted list in the form of
    // List implementations. The List objects returned by these
    // methods are aliases for the underlying sorted list, so modifications
    // made to those lists are directly reflected in the sorted list, and vice
    // versa.
    // 
    // The SortedList class provides a convenient way to create a sorted
    // copy of another dictionary, such as a Hashtable. For example:
    // 
    // Hashtable h = new Hashtable();
    // h.Add(...);
    // h.Add(...);
    // ...
    // SortedList s = new SortedList(h);
    // 
    // The last line above creates a sorted list that contains a copy of the keys
    // and values stored in the hashtable. In this particular example, the keys
    // will be ordered according to the IComparable interface, which they
    // all must implement. To impose a different ordering, SortedList also
    // has a constructor that allows a specific IComparer implementation to
    // be specified.
    // 
    [DebuggerTypeProxy(typeof(System.Collections.SortedList.SortedListDebugView))]  
    [DebuggerDisplay("Count = {Count}")]
    [System.Runtime.InteropServices.ComVisible(true)]
    [Obsolete("Non-generic collections have been deprecated. Please use collections in System.Collections.Generic.")]
    [Serializable]
    public class SortedList : IDictionary, ICloneable
    {
        private Object[] keys;
        private Object[] values;
        private int _size;
        private int version;
        private IComparer comparer;
        private KeyList keyList;
        private ValueList valueList;
        [NonSerialized]
        private Object _syncRoot;
    
        private const int _defaultCapacity = 16;
    
        private static Object[] emptyArray = EmptyArray<Object>.Value; 

        // Constructs a new sorted list. The sorted list is initially empty and has
        // a capacity of zero. Upon adding the first element to the sorted list the
        // capacity is increased to 16, and then increased in multiples of two as
        // required. The elements of the sorted list are ordered according to the
        // IComparable interface, which must be implemented by the keys of
        // all entries added to the sorted list.
        public SortedList() {
            Init();
        }
        private void Init()
        {
            keys = emptyArray;
            values = emptyArray;
            _size = 0;
            comparer = new Comparer(CultureInfo.CurrentCulture);
        }
    
        // Constructs a new sorted list. The sorted list is initially empty and has
        // a capacity of zero. Upon adding the first element to the sorted list the
        // capacity is increased to 16, and then increased in multiples of two as
        // required. The elements of the sorted list are ordered according to the
        // IComparable interface, which must be implemented by the keys of
        // all entries added to the sorted list.
        //
        public SortedList(int initialCapacity) {
            if (initialCapacity < 0)
                throw new ArgumentOutOfRangeException(nameof(initialCapacity), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
            Contract.EndContractBlock();
            keys = new Object[initialCapacity];
            values = new Object[initialCapacity];
            comparer = new Comparer(CultureInfo.CurrentCulture);            
        }
    
        // Constructs a new sorted list with a given IComparer
        // implementation. The sorted list is initially empty and has a capacity of
        // zero. Upon adding the first element to the sorted list the capacity is
        // increased to 16, and then increased in multiples of two as required. The
        // elements of the sorted list are ordered according to the given
        // IComparer implementation. If comparer is null, the
        // elements are compared to each other using the IComparable
        // interface, which in that case must be implemented by the keys of all
        // entries added to the sorted list.
        // 
        public SortedList(IComparer comparer) 
            : this() {
            if (comparer != null) this.comparer = comparer;
        }
    
        // Constructs a new sorted list with a given IComparer
        // implementation and a given initial capacity. The sorted list is
        // initially empty, but will have room for the given number of elements
        // before any reallocations are required. The elements of the sorted list
        // are ordered according to the given IComparer implementation. If
        // comparer is null, the elements are compared to each other using
        // the IComparable interface, which in that case must be implemented
        // by the keys of all entries added to the sorted list.
        // 
        public SortedList(IComparer comparer, int capacity) 
            : this(comparer) {
            Capacity = capacity;
        }
    
        // Constructs a new sorted list containing a copy of the entries in the
        // given dictionary. The elements of the sorted list are ordered according
        // to the IComparable interface, which must be implemented by the
        // keys of all entries in the the given dictionary as well as keys
        // subsequently added to the sorted list.
        // 
        public SortedList(IDictionary d) 
            : this(d, null) {
        }
        
        // Constructs a new sorted list containing a copy of the entries in the
        // given dictionary. The elements of the sorted list are ordered according
        // to the given IComparer implementation. If comparer is
        // null, the elements are compared to each other using the
        // IComparable interface, which in that case must be implemented
        // by the keys of all entries in the the given dictionary as well as keys
        // subsequently added to the sorted list.
        // 
        public SortedList(IDictionary d, IComparer comparer) 
            : this(comparer, (d != null ? d.Count : 0)) {
            if (d==null)
                throw new ArgumentNullException(nameof(d), Environment.GetResourceString("ArgumentNull_Dictionary"));
            Contract.EndContractBlock();
            d.Keys.CopyTo(keys, 0);
            d.Values.CopyTo(values, 0);
            Array.Sort(keys, values, comparer);
            _size = d.Count;
        }
        
        // Adds an entry with the given key and value to this sorted list. An
        // ArgumentException is thrown if the key is already present in the sorted list.
        // 
        public virtual void Add(Object key, Object value) {
            if (key == null) throw new ArgumentNullException(nameof(key), Environment.GetResourceString("ArgumentNull_Key"));
            Contract.EndContractBlock();
            int i = Array.BinarySearch(keys, 0, _size, key, comparer);
            if (i >= 0)
                throw new ArgumentException(Environment.GetResourceString("Argument_AddingDuplicate__", GetKey(i), key));
            Insert(~i, key, value);
        }
        
        // Returns the capacity of this sorted list. The capacity of a sorted list
        // represents the allocated length of the internal arrays used to store the
        // keys and values of the list, and thus also indicates the maximum number
        // of entries the list can contain before a reallocation of the internal
        // arrays is required.
        // 
         public virtual int Capacity {
            get {
                return keys.Length;
            }
            set {
                if (value < Count) {
                    throw new ArgumentOutOfRangeException(nameof(value), Environment.GetResourceString("ArgumentOutOfRange_SmallCapacity"));
                }
                Contract.EndContractBlock();

                if (value != keys.Length) {
                    if (value > 0) {
                        Object[] newKeys = new Object[value];
                        Object[] newValues = new Object[value];
                        if (_size > 0) {
                            Array.Copy(keys, 0, newKeys, 0, _size);
                            Array.Copy(values, 0, newValues, 0, _size);
                        }
                        keys = newKeys;
                        values = newValues;
                    }
                    else {
                        // size can only be zero here.
                        Debug.Assert( _size == 0, "Size is not zero");
                        keys = emptyArray;
                        values = emptyArray;                      
                    }
                }
            }
        }
            
        // Returns the number of entries in this sorted list.
        // 
        public virtual int Count {
            get {
                return _size;
            }
        }
    
        // Returns a collection representing the keys of this sorted list. This
        // method returns the same object as GetKeyList, but typed as an
        // ICollection instead of an IList.
        // 
         public virtual ICollection Keys {
            get {
               return GetKeyList();
            }
        }
    
        // Returns a collection representing the values of this sorted list. This
        // method returns the same object as GetValueList, but typed as an
        // ICollection instead of an IList.
        // 
         public virtual ICollection Values {
            get {
                return GetValueList();
            }
        }
    
        // Is this SortedList read-only?
        public virtual bool IsReadOnly {
            get { return false; }
        }

        public virtual bool IsFixedSize {
            get { return false; }
        }

        // Is this SortedList synchronized (thread-safe)?
        public virtual bool IsSynchronized {
            get { return false; }
        }
    
        // Synchronization root for this object.
        public virtual Object SyncRoot {
            get { 
                if( _syncRoot == null) {
                    System.Threading.Interlocked.CompareExchange<Object>(ref _syncRoot, new Object(), null);    
                }
                return _syncRoot; 
            }
        }
    
        // Removes all entries from this sorted list.
        public virtual void Clear() {
            // clear does not change the capacity
            version++;
            Array.Clear(keys, 0, _size); // Don't need to doc this but we clear the elements so that the gc can reclaim the references.
            Array.Clear(values, 0, _size); // Don't need to doc this but we clear the elements so that the gc can reclaim the references.
            _size = 0;

        }
    
        // Makes a virtually identical copy of this SortedList.  This is a shallow 
        // copy.  IE, the Objects in the SortedList are not cloned - we copy the 
        // references to those objects.
        public virtual Object Clone()
        {
            SortedList sl = new SortedList(_size);
            Array.Copy(keys, 0, sl.keys, 0, _size);
            Array.Copy(values, 0, sl.values, 0, _size);
            sl._size = _size;
            sl.version = version;
            sl.comparer = comparer;
            // Don't copy keyList nor valueList.
            return sl;
        }
    
    
        // Checks if this sorted list contains an entry with the given key.
        // 
        public virtual bool Contains(Object key) {
            return IndexOfKey(key) >= 0;
        }
    
        // Checks if this sorted list contains an entry with the given key.
        // 
        public virtual bool ContainsKey(Object key) {
            // Yes, this is a SPEC'ed duplicate of Contains().
            return IndexOfKey(key) >= 0;
        }
    
        // Checks if this sorted list contains an entry with the given value. The
        // values of the entries of the sorted list are compared to the given value
        // using the Object.Equals method. This method performs a linear
        // search and is substantially slower than the Contains
        // method.
        // 
        public virtual bool ContainsValue(Object value) {
            return IndexOfValue(value) >= 0;
        }
    
        // Copies the values in this SortedList to an array.
        public virtual void CopyTo(Array array, int arrayIndex) {
            if (array == null)
                throw new ArgumentNullException(nameof(array), Environment.GetResourceString("ArgumentNull_Array"));
            if (array.Rank != 1)
                throw new ArgumentException(Environment.GetResourceString("Arg_RankMultiDimNotSupported"));
            if (arrayIndex < 0) 
                throw new ArgumentOutOfRangeException(nameof(arrayIndex), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
            if (array.Length - arrayIndex < Count)
                throw new ArgumentException(Environment.GetResourceString("Arg_ArrayPlusOffTooSmall"));
            Contract.EndContractBlock();
            for (int i = 0; i<Count; i++) {
                DictionaryEntry entry = new DictionaryEntry(keys[i],values[i]);
                array.SetValue(entry, i + arrayIndex);
            }
        }

        // Copies the values in this SortedList to an KeyValuePairs array.
        // KeyValuePairs is different from Dictionary Entry in that it has special
        // debugger attributes on its fields.
        
        internal virtual KeyValuePairs[] ToKeyValuePairsArray() {
            KeyValuePairs[] array = new KeyValuePairs[Count];
            for (int i = 0; i < Count; i++) {
                array[i] = new KeyValuePairs(keys[i],values[i]);
            }
            return array;
        }
        
        // Ensures that the capacity of this sorted list is at least the given
        // minimum value. If the currect capacity of the list is less than
        // min, the capacity is increased to twice the current capacity or
        // to min, whichever is larger.
        private void EnsureCapacity(int min) {
            int newCapacity = keys.Length == 0? 16: keys.Length * 2;
            // Allow the list to grow to maximum possible capacity (~2G elements) before encountering overflow.
            // Note that this check works even when _items.Length overflowed thanks to the (uint) cast
            if ((uint)newCapacity > Array.MaxArrayLength) newCapacity = Array.MaxArrayLength;
            if (newCapacity < min) newCapacity = min;
            Capacity = newCapacity;
        }
    
        // Returns the value of the entry at the given index.
        // 
        public virtual Object GetByIndex(int index) {
            if (index < 0 || index >= Count) 
                throw new ArgumentOutOfRangeException(nameof(index), Environment.GetResourceString("ArgumentOutOfRange_Index"));
            Contract.EndContractBlock();
            return values[index];
        }
    
        // Returns an IEnumerator for this sorted list.  If modifications 
        // made to the sorted list while an enumeration is in progress, 
        // the MoveNext and Remove methods
        // of the enumerator will throw an exception.
        //
        IEnumerator IEnumerable.GetEnumerator() {
            return new SortedListEnumerator(this, 0, _size, SortedListEnumerator.DictEntry);
        }

        // Returns an IDictionaryEnumerator for this sorted list.  If modifications 
        // made to the sorted list while an enumeration is in progress, 
        // the MoveNext and Remove methods
        // of the enumerator will throw an exception.
        //
        public virtual IDictionaryEnumerator GetEnumerator() {
            return new SortedListEnumerator(this, 0, _size, SortedListEnumerator.DictEntry);
        }
        
        // Returns the key of the entry at the given index.
        // 
        public virtual Object GetKey(int index) {
            if (index < 0 || index >= Count) throw new ArgumentOutOfRangeException(nameof(index), Environment.GetResourceString("ArgumentOutOfRange_Index"));
            Contract.EndContractBlock();
            return keys[index];
        }
    
        // Returns an IList representing the keys of this sorted list. The
        // returned list is an alias for the keys of this sorted list, so
        // modifications made to the returned list are directly reflected in the
        // underlying sorted list, and vice versa. The elements of the returned
        // list are ordered in the same way as the elements of the sorted list. The
        // returned list does not support adding, inserting, or modifying elements
        // (the Add, AddRange, Insert, InsertRange,
        // Reverse, Set, SetRange, and Sort methods
        // throw exceptions), but it does allow removal of elements (through the
        // Remove and RemoveRange methods or through an enumerator).
        // Null is an invalid key value.
        // 
        public virtual IList GetKeyList() {
            if (keyList == null) keyList = new KeyList(this);
            return keyList;
        }
    
        // Returns an IList representing the values of this sorted list. The
        // returned list is an alias for the values of this sorted list, so
        // modifications made to the returned list are directly reflected in the
        // underlying sorted list, and vice versa. The elements of the returned
        // list are ordered in the same way as the elements of the sorted list. The
        // returned list does not support adding or inserting elements (the
        // Add, AddRange, Insert and InsertRange
        // methods throw exceptions), but it does allow modification and removal of
        // elements (through the Remove, RemoveRange, Set and
        // SetRange methods or through an enumerator).
        // 
        public virtual IList GetValueList() {
            if (valueList == null) valueList = new ValueList(this);
            return valueList;
        }
    
        // Returns the value associated with the given key. If an entry with the
        // given key is not found, the returned value is null.
        // 
        public virtual Object this[Object key] {
            get {
                int i = IndexOfKey(key);
                if (i >= 0) return values[i];
                return null;
            }
            set {
                if (key == null) throw new ArgumentNullException(nameof(key), Environment.GetResourceString("ArgumentNull_Key"));
                Contract.EndContractBlock();
                int i = Array.BinarySearch(keys, 0, _size, key, comparer);
                if (i >= 0) {
                    values[i] = value;
                    version++;
                    return;
                }
                Insert(~i, key, value);
            }
        }
    
        // Returns the index of the entry with a given key in this sorted list. The
        // key is located through a binary search, and thus the average execution
        // time of this method is proportional to Log2(size), where
        // size is the size of this sorted list. The returned value is -1 if
        // the given key does not occur in this sorted list. Null is an invalid 
        // key value.
        // 
        public virtual int IndexOfKey(Object key) {
            if (key == null) 
                throw new ArgumentNullException(nameof(key), Environment.GetResourceString("ArgumentNull_Key"));
            Contract.EndContractBlock();
            int ret = Array.BinarySearch(keys, 0, _size, key, comparer);
            return ret >=0 ? ret : -1;
        }
    
        // Returns the index of the first occurrence of an entry with a given value
        // in this sorted list. The entry is located through a linear search, and
        // thus the average execution time of this method is proportional to the
        // size of this sorted list. The elements of the list are compared to the
        // given value using the Object.Equals method.
        // 
        public virtual int IndexOfValue(Object value) {
            return Array.IndexOf(values, value, 0, _size);
        }
    
        // Inserts an entry with a given key and value at a given index.
        private void Insert(int index, Object key, Object value) {
            if (_size == keys.Length) EnsureCapacity(_size + 1);
            if (index < _size) {
                Array.Copy(keys, index, keys, index + 1, _size - index);
                Array.Copy(values, index, values, index + 1, _size - index);
            }
            keys[index] = key;
            values[index] = value;
            _size++;
            version++;
        }
    
        // Removes the entry at the given index. The size of the sorted list is
        // decreased by one.
        // 
        public virtual void RemoveAt(int index) {
            if (index < 0 || index >= Count) throw new ArgumentOutOfRangeException(nameof(index), Environment.GetResourceString("ArgumentOutOfRange_Index"));
            Contract.EndContractBlock();
            _size--;
            if (index < _size) {
                Array.Copy(keys, index + 1, keys, index, _size - index);
                Array.Copy(values, index + 1, values, index, _size - index);
            }
            keys[_size] = null;
            values[_size] = null;
            version++;
        }
    
        // Removes an entry from this sorted list. If an entry with the specified
        // key exists in the sorted list, it is removed. An ArgumentException is
        // thrown if the key is null.
        // 
        public virtual void Remove(Object key) {
            int i = IndexOfKey(key);
            if (i >= 0) 
            RemoveAt(i);
        }
    
        // Sets the value at an index to a given value.  The previous value of
        // the given entry is overwritten.
        // 
        public virtual void SetByIndex(int index, Object value) {
            if (index < 0 || index >= Count) throw new ArgumentOutOfRangeException(nameof(index), Environment.GetResourceString("ArgumentOutOfRange_Index"));
            Contract.EndContractBlock();
            values[index] = value;
            version++;
        }
        
        // Returns a thread-safe SortedList.
        //
        public static SortedList Synchronized(SortedList list) {
            if (list==null)
                throw new ArgumentNullException(nameof(list));
            Contract.EndContractBlock();
            return new SyncSortedList(list);
        }
      
        // Sets the capacity of this sorted list to the size of the sorted list.
        // This method can be used to minimize a sorted list's memory overhead once
        // it is known that no new elements will be added to the sorted list. To
        // completely clear a sorted list and release all memory referenced by the
        // sorted list, execute the following statements:
        // 
        // sortedList.Clear();
        // sortedList.TrimToSize();
        // 
        public virtual void TrimToSize() {
            Capacity = _size;
        }
    
        [Serializable]
        private class SyncSortedList : SortedList
        {
            private SortedList _list;
            private Object _root;

    
            internal SyncSortedList(SortedList list) {
                _list = list;
                _root = list.SyncRoot;
            }
    
            public override int Count { 
                get { lock(_root) { return _list.Count; } }
            }
    
            public override Object SyncRoot {
                get { return _root; }
            }

            public override bool IsReadOnly {
                get { return _list.IsReadOnly; }
            }

            public override bool IsFixedSize {
                get { return _list.IsFixedSize; }
            }


            public override bool IsSynchronized { 
                get { return true; }
            }
            
            public override Object this[Object key] {
                get {
                    lock(_root) {
                        return _list[key];
                    }
                }
                set {
                    lock(_root) {
                        _list[key] = value;
                    }
                }
            }
    
            public override void Add(Object key, Object value) {
                lock(_root) {
                    _list.Add(key, value);
                }
            }
    
            public override int Capacity {
                get{ lock(_root) {  return _list.Capacity; } }
            }

            public override void Clear() {
                lock(_root) {
                    _list.Clear();
                }
            }

            public override Object Clone() {
                lock(_root) {
                    return _list.Clone();
                }
            }

            public override bool Contains(Object key) {
                lock(_root) {
                    return _list.Contains(key);
                }
            }
    
            public override bool ContainsKey(Object key) {
                lock(_root) {
                    return _list.ContainsKey(key);
                }
            }
    
            public override bool ContainsValue(Object key) {
                lock(_root) {
                    return _list.ContainsValue(key);
                }
            }
    
            public override void CopyTo(Array array, int index) {
                lock(_root) {
                    _list.CopyTo(array, index);
                }
            }

            [SuppressMessage("Microsoft.Contracts", "CC1055")]  // Skip extra error checking to avoid *potential* AppCompat problems.
            public override Object GetByIndex(int index) {
                lock(_root) {
                    return _list.GetByIndex(index);
                }
            }
    
            public override IDictionaryEnumerator GetEnumerator() {
                lock(_root) {
                    return _list.GetEnumerator();
                }
            }

            [SuppressMessage("Microsoft.Contracts", "CC1055")]  // Skip extra error checking to avoid *potential* AppCompat problems.
            public override Object GetKey(int index) {
                lock(_root) {
                    return _list.GetKey(index);
                }
            }
    
            public override IList GetKeyList() {
                lock(_root) {
                    return _list.GetKeyList();
                }
            }
    
            public override IList GetValueList() {
                lock(_root) {
                    return _list.GetValueList();
                }
            }
    
            public override int IndexOfKey(Object key) {
                if (key == null)
                    throw new ArgumentNullException(nameof(key), Environment.GetResourceString("ArgumentNull_Key"));
                Contract.EndContractBlock();

                lock(_root) {
                    return _list.IndexOfKey(key);
                }
            }

            [SuppressMessage("Microsoft.Contracts", "CC1055")]  // Skip extra error checking to avoid *potential* AppCompat problems.
            public override int IndexOfValue(Object value) {
                lock(_root) {
                    return _list.IndexOfValue(value);
                }
            }

            [SuppressMessage("Microsoft.Contracts", "CC1055")]  // Skip extra error checking to avoid *potential* AppCompat problems.
            public override void RemoveAt(int index) {
                lock(_root) {
                    _list.RemoveAt(index);
                }
            }
    
            public override void Remove(Object key) {
                lock(_root) {
                    _list.Remove(key);
                }
            }

            [SuppressMessage("Microsoft.Contracts", "CC1055")]  // Skip extra error checking to avoid *potential* AppCompat problems.
            public override void SetByIndex(int index, Object value) {
                lock(_root) {
                    _list.SetByIndex(index, value);
                }
            }
    
            internal override KeyValuePairs[] ToKeyValuePairsArray() {
                return _list.ToKeyValuePairsArray();
            }

            public override void TrimToSize() {
                lock(_root) {
                    _list.TrimToSize();
                }
            }
        }
    
    
        [Serializable]
        private class SortedListEnumerator : IDictionaryEnumerator, ICloneable
        {
            private SortedList sortedList;
            private Object key;
            private Object value;
            private int index;
            private int startIndex;        // Store for Reset.
            private int endIndex;
            private int version;
            private bool current;       // Is the current element valid?
            private int getObjectRetType;  // What should GetObject return?
    
            internal const int Keys = 1;
            internal const int Values = 2;
            internal const int DictEntry = 3;
    
            internal SortedListEnumerator(SortedList sortedList, int index, int count, 
                                 int getObjRetType) {
                this.sortedList = sortedList;
                this.index = index;
                startIndex = index;
                endIndex = index + count;
                version = sortedList.version;
                getObjectRetType = getObjRetType;
                current = false;
            }
    
            public Object Clone()
            {
                return MemberwiseClone();
            }

            public virtual Object Key {
                get {
                    if (version != sortedList.version) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumFailedVersion"));
                    if (current == false) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumOpCantHappen"));
                    return key;
                }
            }
    
            public virtual bool MoveNext() {
                if (version != sortedList.version) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumFailedVersion"));
                if (index < endIndex) {
                    key = sortedList.keys[index];
                    value = sortedList.values[index];
                    index++;
                    current = true;
                    return true;
                }
                key = null;
                value = null;
                current = false;
                return false;
            }
    
            public virtual DictionaryEntry Entry {
                get {
                    if (version != sortedList.version) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumFailedVersion"));
                    if (current == false) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumOpCantHappen"));
                    return new DictionaryEntry(key, value);
                }
            }
    
            public virtual Object Current {
                get {
                    if (current == false) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumOpCantHappen"));
                    
                    if (getObjectRetType==Keys)
                        return key;
                    else if (getObjectRetType==Values)
                        return value;
                    else 
                        return new DictionaryEntry(key, value);
                }
            }
    
            public virtual Object Value {
                get {
                    if (version != sortedList.version) throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumFailedVersion));
                    if (current == false) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumOpCantHappen"));
                    return value;
                }
            }
            
            public virtual void Reset() {
                if (version != sortedList.version) throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumFailedVersion));
                index = startIndex;
                current = false;
                key = null;
                value = null;
            }
        }
    
        [Serializable]
        private class KeyList : IList
        {
            private SortedList sortedList;
    
            internal KeyList(SortedList sortedList) {
                this.sortedList = sortedList;
            }
    
            public virtual int Count { 
                get { return sortedList._size; }
            }
    
            public virtual bool IsReadOnly {
                get { return true; }
            }

            public virtual bool IsFixedSize {
                get { return true; }
            }

            public virtual bool IsSynchronized {
                get { return sortedList.IsSynchronized; }
            }
    
            public virtual Object SyncRoot {
                get { return sortedList.SyncRoot; }
            }
    
            public virtual int Add(Object key) {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
                //            return 0; // suppress compiler warning
            }
    
            public virtual void Clear() {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
            }
    
            public virtual bool Contains(Object key) {
                return sortedList.Contains(key);
            }
    
            public virtual void CopyTo(Array array, int arrayIndex) {
                if (array != null && array.Rank != 1)
                    throw new ArgumentException(Environment.GetResourceString("Arg_RankMultiDimNotSupported"));
                Contract.EndContractBlock();
                
                // defer error checking to Array.Copy
                Array.Copy(sortedList.keys, 0, array, arrayIndex, sortedList.Count);
            }
    
            public virtual void Insert(int index, Object value) {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
            }
    
            public virtual Object this[int index] {
                get {
                    return sortedList.GetKey(index);
                }
                set {
                    throw new NotSupportedException(Environment.GetResourceString("NotSupported_KeyCollectionSet"));
                }
            }
    
            public virtual IEnumerator GetEnumerator() {
                return new SortedListEnumerator(sortedList, 0, sortedList.Count, SortedListEnumerator.Keys);
            }
    
            public virtual int IndexOf(Object key) {
                if (key==null)
                    throw new ArgumentNullException(nameof(key), Environment.GetResourceString("ArgumentNull_Key"));
                Contract.EndContractBlock();
    
                int i = Array.BinarySearch(sortedList.keys, 0,
                                           sortedList.Count, key, sortedList.comparer);
                if (i >= 0) return i;
                return -1;
            }
    
            public virtual void Remove(Object key) {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
            }
    
            public virtual void RemoveAt(int index) {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
            }
        }
    
        [Serializable]
        private class ValueList : IList
        {
            private SortedList sortedList;
    
            internal ValueList(SortedList sortedList) {
                this.sortedList = sortedList;
            }
    
            public virtual int Count { 
                get { return sortedList._size; }
            }
    
            public virtual bool IsReadOnly {
                get { return true; }
            }

            public virtual bool IsFixedSize {
                get { return true; }
            }

            public virtual bool IsSynchronized {
                get { return sortedList.IsSynchronized; }
            }
    
            public virtual Object SyncRoot {
                get { return sortedList.SyncRoot; }
            }
    
            public virtual int Add(Object key) {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
            }
    
            public virtual void Clear() {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
            }
    
            public virtual bool Contains(Object value) {
                return sortedList.ContainsValue(value);
            }
    
            public virtual void CopyTo(Array array, int arrayIndex) {
                if (array != null && array.Rank != 1)
                    throw new ArgumentException(Environment.GetResourceString("Arg_RankMultiDimNotSupported"));
                Contract.EndContractBlock();
                
                // defer error checking to Array.Copy
                Array.Copy(sortedList.values, 0, array, arrayIndex, sortedList.Count);
            }
    
            public virtual void Insert(int index, Object value) {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
            }
    
            public virtual Object this[int index] {
                get {
                    return sortedList.GetByIndex(index);
                }
                set {
                    throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
                }
            }

            public virtual IEnumerator GetEnumerator() {
                return new SortedListEnumerator(sortedList, 0, sortedList.Count, SortedListEnumerator.Values);
            }
    
            public virtual int IndexOf(Object value) {
                return Array.IndexOf(sortedList.values, value, 0, sortedList.Count);
            }
    
            public virtual void Remove(Object value) {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
            }
    
            public virtual void RemoveAt(int index) {
                throw new NotSupportedException(Environment.GetResourceString(ResId.NotSupported_SortedListNestedWrite));
            }
            
        }
        
        // internal debug view class for sorted list
        internal class SortedListDebugView {
            private SortedList sortedList; 
        
            public SortedListDebugView( SortedList sortedList) {
                if( sortedList == null) {
                    throw new ArgumentNullException(nameof(sortedList));
                }
                Contract.EndContractBlock();

                this.sortedList = sortedList;            
            }
       
            [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
            public KeyValuePairs[] Items { 
                get {
                    return sortedList.ToKeyValuePairsArray();               
                }
            }
        }        
    }
}