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// 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.
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Reflection;
using System.Threading;
namespace System.ComponentModel
{
/// <summary>
/// Specifies the default value for a property.
/// </summary>
[SuppressMessage("Microsoft.Design", "CA1019:DefineAccessorsForAttributeArguments")]
[SuppressMessage("Microsoft.Performance", "CA1813:AvoidUnsealedAttributes")]
[AttributeUsage(AttributeTargets.All)]
public class DefaultValueAttribute : Attribute
{
/// <summary>
/// This is the default value.
/// </summary>
private object? _value;
// Delegate ad hoc created 'TypeDescriptor.ConvertFromInvariantString' reflection object cache
private static object? s_convertFromInvariantString;
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class, converting the specified value to the specified type, and using the U.S. English
/// culture as the translation context.
/// </summary>
public DefaultValueAttribute(Type type, string? value)
{
// The null check and try/catch here are because attributes should never throw exceptions.
// We would fail to load an otherwise normal class.
if (type == null)
{
return;
}
try
{
if (TryConvertFromInvariantString(type, value, out object? convertedValue))
{
_value = convertedValue;
}
else if (type.IsSubclassOf(typeof(Enum)) && value != null)
{
_value = Enum.Parse(type, value, true);
}
else if (type == typeof(TimeSpan) && value != null)
{
_value = TimeSpan.Parse(value);
}
else
{
_value = Convert.ChangeType(value, type, CultureInfo.InvariantCulture);
}
// Looking for ad hoc created TypeDescriptor.ConvertFromInvariantString(Type, string)
bool TryConvertFromInvariantString(Type? typeToConvert, string? stringValue, out object? conversionResult)
{
conversionResult = null;
// lazy init reflection objects
if (s_convertFromInvariantString == null)
{
Type? typeDescriptorType = Type.GetType("System.ComponentModel.TypeDescriptor, System.ComponentModel.TypeConverter", throwOnError: false);
MethodInfo? mi = typeDescriptorType?.GetMethod("ConvertFromInvariantString", BindingFlags.NonPublic | BindingFlags.Static);
Volatile.Write(ref s_convertFromInvariantString, mi == null ? new object() : mi.CreateDelegate(typeof(Func<Type, string, object>)));
}
if (!(s_convertFromInvariantString is Func<Type?, string?, object> convertFromInvariantString))
return false;
try
{
conversionResult = convertFromInvariantString(typeToConvert, stringValue);
}
catch
{
return false;
}
return true;
}
}
catch
{
}
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a Unicode character.
/// </summary>
public DefaultValueAttribute(char value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using an 8-bit unsigned integer.
/// </summary>
public DefaultValueAttribute(byte value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a 16-bit signed integer.
/// </summary>
public DefaultValueAttribute(short value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a 32-bit signed integer.
/// </summary>
public DefaultValueAttribute(int value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a 64-bit signed integer.
/// </summary>
public DefaultValueAttribute(long value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a single-precision floating point number.
/// </summary>
public DefaultValueAttribute(float value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a double-precision floating point number.
/// </summary>
public DefaultValueAttribute(double value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a <see cref='System.Boolean'/> value.
/// </summary>
public DefaultValueAttribute(bool value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a <see cref='System.String'/>.
/// </summary>
public DefaultValueAttribute(string? value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class.
/// </summary>
public DefaultValueAttribute(object? value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a <see cref='System.SByte'/> value.
/// </summary>
[CLSCompliant(false)]
public DefaultValueAttribute(sbyte value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a <see cref='System.UInt16'/> value.
/// </summary>
[CLSCompliant(false)]
public DefaultValueAttribute(ushort value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a <see cref='System.UInt32'/> value.
/// </summary>
[CLSCompliant(false)]
public DefaultValueAttribute(uint value)
{
_value = value;
}
/// <summary>
/// Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
/// class using a <see cref='System.UInt64'/> value.
/// </summary>
[CLSCompliant(false)]
public DefaultValueAttribute(ulong value)
{
_value = value;
}
/// <summary>
/// Gets the default value of the property this attribute is bound to.
/// </summary>
public virtual object? Value => _value;
public override bool Equals(object? obj)
{
if (obj == this)
{
return true;
}
if (!(obj is DefaultValueAttribute other))
{
return false;
}
if (Value == null)
{
return other.Value == null;
}
return Value.Equals(other.Value);
}
public override int GetHashCode() => base.GetHashCode();
protected void SetValue(object? value) => _value = value;
}
}
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