Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / System / Windows / Data / PriorityBindingExpression.cs / 1305600 / PriorityBindingExpression.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // Description: Defines PriorityBindingExpression object, which chooses a BindingExpression out // of a list of BindingExpressions in order of "priority" (and falls back // to the next BindingExpression as each BindingExpression fails) // // See spec at http://avalon/connecteddata/Specs/Data%20Binding.mht // //--------------------------------------------------------------------------- using System; using System.Collections; using System.Collections.ObjectModel; // Collectionusing System.Diagnostics; using System.Threading; using System.Windows.Controls; // ValidationStep using System.Windows.Threading; using System.Windows.Markup; using MS.Internal; using MS.Internal.Data; using MS.Utility; namespace System.Windows.Data { /// /// Describes a collection of BindingExpressions attached to a single property. /// These behave as "priority" BindingExpressions, meaning that the property /// receives its value from the first BindingExpression in the collection that /// can produce a legal value. /// public sealed class PriorityBindingExpression : BindingExpressionBase { //----------------------------------------------------- // // Constructors // //----------------------------------------------------- private PriorityBindingExpression(PriorityBinding binding, BindingExpressionBase owner) : base(binding, owner) { } //------------------------------------------------------ // // Public Properties // //----------------------------------------------------- ///Binding from which this expression was created public PriorityBinding ParentPriorityBinding { get { return (PriorityBinding)ParentBindingBase; } } ///List of inner BindingExpression public ReadOnlyCollectionBindingExpressions { get { return new ReadOnlyCollection (MutableBindingExpressions); } } /// Returns the active BindingExpression (or null) public BindingExpressionBase ActiveBindingExpression { get { return (_activeIndex < 0) ? null : MutableBindingExpressions[_activeIndex]; } } //------------------------------------------------------ // // Public Methods // //------------------------------------------------------ ///Force a data transfer from source to target public override void UpdateTarget() { BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { bindExpr.UpdateTarget(); } } ///Send the current value back to the source ///Does nothing when binding's Mode is not TwoWay or OneWayToSource public override void UpdateSource() { BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { bindExpr.UpdateSource(); } } #region Expression overrides ////// Called to evaluate the Expression value /// /// DependencyObject being queried /// Property being queried ///Computed value. Unset if unavailable. internal override object GetValue(DependencyObject d, DependencyProperty dp) { return Value; } ////// Allows Expression to store set values /// /// DependencyObject being set /// Property being set /// Value being set ///true if Expression handled storing of the value internal override bool SetValue(DependencyObject d, DependencyProperty dp, object value) { bool result; BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { result = bindExpr.SetValue(d, dp, value); if (result) { // the active binding's value becomes the value of the priority binding Value = bindExpr.Value; } } else { // If we couldn't find the active binding, just return true to keep the property // engine from removing the PriorityBinding. result = true; } return result; } #endregion Expression overrides //----------------------------------------------------- // // Internal Methods // //------------------------------------------------------ // Create a new BindingExpression from the given Binding description internal static PriorityBindingExpression CreateBindingExpression(DependencyObject d, DependencyProperty dp, PriorityBinding binding, BindingExpressionBase owner) { FrameworkPropertyMetadata fwMetaData = dp.GetMetadata(d.DependencyObjectType) as FrameworkPropertyMetadata; if ((fwMetaData != null && !fwMetaData.IsDataBindingAllowed) || dp.ReadOnly) throw new ArgumentException(SR.Get(SRID.PropertyNotBindable, dp.Name), "dp"); // create the BindingExpression PriorityBindingExpression bindExpr = new PriorityBindingExpression(binding, owner); return bindExpr; } //----------------------------------------------------- // // Protected Internal Properties // //----------------------------------------------------- ////// Number of BindingExpressions that have been attached and are listening /// internal int AttentiveBindingExpressions { get { return (_activeIndex == NoActiveBindingExpressions) ? MutableBindingExpressions.Count : _activeIndex + 1; } } //----------------------------------------------------- // // Protected Internal Methods // //------------------------------------------------------ ////// Attach a BindingExpression to the given target (element, property) /// /// DependencyObject being set /// Property being set internal override bool AttachOverride(DependencyObject d, DependencyProperty dp) { if (!base.AttachOverride(d, dp)) return false; DependencyObject target = TargetElement; if (target == null) return false; SetStatus(BindingStatus.Active); int count = ParentPriorityBinding.Bindings.Count; _activeIndex = NoActiveBindingExpressions; Debug.Assert(MutableBindingExpressions.Count == 0, "expect to encounter empty BindingExpression collection when attaching MultiBinding"); for (int i = 0; i < count; ++i) { AttachBindingExpression(i, false); // create new binding and have it added to end } return true; } ///sever all connections internal override void DetachOverride() { // Theoretically, we only need to detach number of AttentiveBindings, // but we'll traverse the whole list anyway and do aggressive clean-up. int count = MutableBindingExpressions.Count; for (int i = 0; i < count; ++i) { BindingExpressionBase b = MutableBindingExpressions[i]; if (b != null) b.Detach(); } ChangeSources(null); base.DetachOverride(); } ////// Invalidate the given child expression. /// internal override void InvalidateChild(BindingExpressionBase bindingExpression) { // Prevent re-entrancy, because ChooseActiveBindingExpression() may // activate/deactivate a BindingExpression that indirectly calls this again. if (_isInInvalidateBinding) return; _isInInvalidateBinding = true; int index = MutableBindingExpressions.IndexOf(bindingExpression); DependencyObject target = TargetElement; if (target != null && 0 <= index && index < AttentiveBindingExpressions) { // Optimization: only look for new ActiveBindingExpression when necessary: // 1. it is a higher priority BindingExpression (or there's no ActiveBindingExpression), or // 2. the existing ActiveBindingExpression is broken if ( index != _activeIndex || (bindingExpression.Status != BindingStatus.Active && !bindingExpression.UsingFallbackValue)) { ChooseActiveBindingExpression(target); } // update the value UsingFallbackValue = false; BindingExpressionBase bindExpr = ActiveBindingExpression; object newValue = (bindExpr != null) ? bindExpr.GetValue(target, TargetProperty) : UseFallbackValue(); ChangeValue(newValue, true); if (TraceData.IsExtendedTraceEnabled(this, TraceDataLevel.Transfer)) { TraceData.Trace(TraceEventType.Warning, TraceData.PriorityTransfer( TraceData.Identify(this), TraceData.Identify(newValue), _activeIndex, TraceData.Identify(bindExpr))); } // don't invalidate during Attach. The property engine does it // already, and it would interfere with the on-demand activation // of style-defined BindingExpressions. if (!IsAttaching) { // recompute expression target.InvalidateProperty(TargetProperty); } } _isInInvalidateBinding = false; } ////// Change the dependency sources for the given child expression. /// internal override void ChangeSourcesForChild(BindingExpressionBase bindingExpression, WeakDependencySource[] newSources) { int index = MutableBindingExpressions.IndexOf(bindingExpression); if (index >= 0) { WeakDependencySource[] combinedSources = CombineSources(index, MutableBindingExpressions, AttentiveBindingExpressions, newSources); ChangeSources(combinedSources); } } ////// Replace the given child expression with a new one. /// internal override void ReplaceChild(BindingExpressionBase bindingExpression) { int index = MutableBindingExpressions.IndexOf(bindingExpression); DependencyObject target = TargetElement; if (index >= 0 && target != null) { // clean up the old BindingExpression bindingExpression.Detach(); // create a replacement BindingExpression and put it in the collection bindingExpression = AttachBindingExpression(index, true); } } // register the leaf bindings with the binding group internal override void UpdateBindingGroup(BindingGroup bg) { for (int i=0, n=MutableBindingExpressions.Count-1; i/// Get the raw proposed value /// internal override object GetRawProposedValue() { BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { return bindExpr.GetRawProposedValue(); } return DependencyProperty.UnsetValue; } /// /// Get the converted proposed value /// internal override object ConvertProposedValue(object rawValue) { BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { return bindExpr.ConvertProposedValue(rawValue); } return DependencyProperty.UnsetValue; } /// /// Get the converted proposed value and inform the binding group /// internal override bool ObtainConvertedProposedValue(BindingGroup bindingGroup) { BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { return bindExpr.ObtainConvertedProposedValue(bindingGroup); } return true; } /// /// Update the source value /// internal override object UpdateSource(object convertedValue) { object result; BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { result = bindExpr.UpdateSource(convertedValue); if (bindExpr.Status == BindingStatus.UpdateSourceError) { SetStatus(BindingStatus.UpdateSourceError); } } else { result = DependencyProperty.UnsetValue; } return result; } /// /// Update the source value and inform the binding group /// internal override bool UpdateSource(BindingGroup bindingGroup) { bool result = true; BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { result = bindExpr.UpdateSource(bindingGroup); if (bindExpr.Status == BindingStatus.UpdateSourceError) { SetStatus(BindingStatus.UpdateSourceError); } } return result; } /// /// Store the value in the binding group /// internal override void StoreValueInBindingGroup(object value, BindingGroup bindingGroup) { BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { bindExpr.StoreValueInBindingGroup(value, bindingGroup); } } ////// Run validation rules for the given step /// internal override bool Validate(object value, ValidationStep validationStep) { BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { return bindExpr.Validate(value, validationStep); } return true; } /// /// Run validation rules for the given step, and inform the binding group /// internal override bool CheckValidationRules(BindingGroup bindingGroup, ValidationStep validationStep) { BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { return bindExpr.CheckValidationRules(bindingGroup, validationStep); } return true; } /// /// Get the proposed value(s) that would be written to the source(s), applying /// conversion and checking UI-side validation rules. /// internal override bool ValidateAndConvertProposedValue(out Collectionvalues) { Debug.Assert(NeedsValidation, "check NeedsValidation before calling this"); BindingExpressionBase bindExpr = ActiveBindingExpression; if (bindExpr != null) { return bindExpr.ValidateAndConvertProposedValue(out values); } values = null; return true; } //----------------------------------------------------- // // Private Properties // //------------------------------------------------------ /// /// expose a mutable version of the list of all BindingExpressions; /// derived internal classes need to be able to populate this list /// private CollectionMutableBindingExpressions { get { return _list; } } //------------------------------------------------------ // // Private Methods // //----------------------------------------------------- // Create a BindingExpression for position i BindingExpressionBase AttachBindingExpression(int i, bool replaceExisting) { DependencyObject target = TargetElement; if (target == null) return null; BindingBase binding = ParentPriorityBinding.Bindings[i]; BindingExpressionBase bindExpr = binding.CreateBindingExpression(target, TargetProperty, this); if (replaceExisting) // replace exisiting or add as new binding? MutableBindingExpressions[i] = bindExpr; else MutableBindingExpressions.Add(bindExpr); bindExpr.Attach(target, TargetProperty); return bindExpr; } // Re-evaluate the choice of active BindingExpression void ChooseActiveBindingExpression(DependencyObject target) { int i, count = MutableBindingExpressions.Count; for (i = 0; i < count; ++i) { BindingExpressionBase bindExpr = MutableBindingExpressions[i]; // Try to activate the BindingExpression if it isn't already activate if (bindExpr.Status == BindingStatus.Inactive) bindExpr.Activate(); if (bindExpr.Status == BindingStatus.Active || bindExpr.UsingFallbackValue) break; } int newActiveIndex = (i < count) ? i : NoActiveBindingExpressions; // if active changes, tell the property engine the new list of sources if (newActiveIndex != _activeIndex) { int oldActiveIndex = _activeIndex; // get new list of sources _activeIndex = newActiveIndex; WeakDependencySource[] newSources = CombineSources(-1, MutableBindingExpressions, AttentiveBindingExpressions, null); // tell property engine ChangeSources(newSources); // deactivate BindingExpressions that don't need to be attentive // if (newActiveIndex != NoActiveBindingExpressions) for (i = oldActiveIndex; i > newActiveIndex; --i) MutableBindingExpressions[i].Deactivate(); } } private void ChangeValue() { } internal override void HandlePropertyInvalidation(DependencyObject d, DependencyPropertyChangedEventArgs args) { DependencyProperty dp = args.Property; int n = AttentiveBindingExpressions; if (TraceData.IsExtendedTraceEnabled(this, TraceDataLevel.Events)) { TraceData.Trace(TraceEventType.Warning, TraceData.GotPropertyChanged( TraceData.Identify(this), TraceData.Identify(d), dp.Name)); } for (int i=0; i _list = new Collection (); int _activeIndex = UnknownActiveBindingExpression; bool _isInInvalidateBinding = false; } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. 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