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/ DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / MS / Internal / Data / DynamicValueConverter.cs / 3 / DynamicValueConverter.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // Description: wrapper around default converter to dynamcially pick // and change value converters depending on changing source and target types // //--------------------------------------------------------------------------- using System; using System.Globalization; using System.Collections; using System.ComponentModel; using System.Reflection; using System.Windows; using System.Windows.Data; using MS.Internal; // Invariant.Assert using System.Diagnostics; namespace MS.Internal.Data { // dynamically pick and switch a default value converter to convert between source and target type internal class DynamicValueConverter : IValueConverter { internal DynamicValueConverter(bool targetToSourceNeeded) { _targetToSourceNeeded = targetToSourceNeeded; } internal DynamicValueConverter(bool targetToSourceNeeded, Type sourceType, Type targetType) { _targetToSourceNeeded = targetToSourceNeeded; EnsureConverter(sourceType, targetType); } internal object Convert(object value, Type targetType) { return Convert(value, targetType, null, CultureInfo.InvariantCulture); } public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { object result = DependencyProperty.UnsetValue; // meaning: failure to convert if (value != null) { Type sourceType = value.GetType(); EnsureConverter(sourceType, targetType); if (_converter != null) { result = _converter.Convert(value, targetType, parameter, culture); } } else { if (!targetType.IsValueType) { result = null; } } return result; } public object ConvertBack(object value, Type sourceType, object parameter, CultureInfo culture) { object result = DependencyProperty.UnsetValue; // meaning: failure to convert if (value != null) { Type targetType = value.GetType(); EnsureConverter(sourceType, targetType); if (_converter != null) { result = _converter.ConvertBack(value, sourceType, parameter, culture); } } else { if (!sourceType.IsValueType) { result = null; } } return result; } private void EnsureConverter(Type sourceType, Type targetType) { if ((_sourceType != sourceType) || (_targetType != targetType)) { // types have changed - get a new converter if (sourceType != null && targetType != null) { // DefaultValueConverter.Create() is more sophisticated to find correct type converters, // e.g. if source/targetType is object or well-known system types. // if there is any change in types, give that code to come up with the correct converter if (_engine == null) { _engine = DataBindEngine.CurrentDataBindEngine; } Invariant.Assert(_engine != null); _converter = _engine.GetDefaultValueConverter(sourceType, targetType, _targetToSourceNeeded); } else { // if either type is null, no conversion is possible. // Don't ask GetDefaultValueConverter - it will use null as a // hashtable key, and crash (bug 110859). _converter = null; } _sourceType = sourceType; _targetType = targetType; } } private Type _sourceType; private Type _targetType; private IValueConverter _converter; private bool _targetToSourceNeeded; private DataBindEngine _engine; } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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