ValueConversionAttribute.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / System / Windows / Data / ValueConversionAttribute.cs / 1305600 / ValueConversionAttribute.cs
                        

                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: allows the author of a IValueConverter 
//              to specify what source and target property types the 
//              ValueConverter is capable of converting
// 
// Specs:       http://avalon/connecteddata/Specs/Data%20Binding.mht
//
//---------------------------------------------------------------------------
 
using System;
 
namespace System.Windows.Data 
{
 

    /// 
    ///     This attribute allows the author of a 
    ///     to specify what source and target property types the ValueConverter is capable of converting. 
    ///     This meta data is useful for designer tools to help categorize and match ValueConverters.
    ///  
    ///  
    /// Add this custom attribute to your IValueConverter class definition.
    ///  
    ///     [ValueConversion(typeof(Employee), typeof(Brush))]
    ///     class MyConverter : IValueConverter
    ///     {
    ///         public object Convert(object value, Type targetType, object parameter, CultureInfo culture) 
    ///         {
    ///             if (value is Dev)       return Brushes.Beige; 
    ///             if (value is Employee)  return Brushes.Salmon; 
    ///             return Brushes.Yellow;
    ///         } 
    ///     }
    /// 
    /// 
    [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)] 
    public sealed class ValueConversionAttribute : Attribute
    { 
        //----------------------------------------------------- 
        //
        //  Constructors 
        //
        //-----------------------------------------------------

        ///  
        ///     Creates a new ValueConversionAttribute to indicate between
        ///     what types of a data binding source and target this ValueConverter can convert. 
        ///  
        /// the expected source type this ValueConverter can handle
        /// the target type to which this ValueConverter can convert to 
        public ValueConversionAttribute(Type sourceType, Type targetType)
        {
            if (sourceType == null)
                throw new ArgumentNullException("sourceType"); 
            if (targetType == null)
                throw new ArgumentNullException("targetType"); 
            _sourceType = sourceType; 
            _targetType = targetType;
        } 

        /// 
        ///     The expected source type this ValueConverter can handle.
        ///  
        public Type SourceType
        { 
            get { return _sourceType; } 
        }
 
        /// 
        ///     The target type to which this ValueConverter can convert to.
        /// 
        public Type TargetType 
        {
            get { return _targetType; } 
        } 

        ///  
        ///     The type of the optional ValueConverter Parameter object.
        /// 
        public Type ParameterType
        { 
            get { return _parameterType; }
            set { _parameterType = value; } 
        } 

        /// 
        ///     Returns the unique identifier for this Attribute.
        ///
        // Type ID is used to remove redundant attributes by
        // putting all attributes in a dictionary of [TypeId, Attribute]. 
        // If you want AllowMultiple attributes to work with designers,
        // you must override TypeId.  The default implementation returns 
        // this.GetType(), which is appropriate for AllowMultiple = false, but 
        // not for AllowMultiple = true;
        public override object TypeId 
        {
             // the attribute itself will be used as a key to the dictionary
            get { return this; }
        } 

        /// 
        ///     Returns the hash code for this instance. 
        ///
        override public int GetHashCode() 
        {
            // the default implementation does some funky enumeration over its fields
            // we can do better and use the 2 mandatory fields source/targetType's hash codes
            return _sourceType.GetHashCode() + _targetType.GetHashCode(); 
        }
 
 
        //--------------------------------------------
        // Private members 
        //--------------------------------------------
        private Type _sourceType;
        private Type _targetType;
        private Type _parameterType; 

    } 
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.

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