using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Linq.Expressions;
namespace BindingSample
{
/// <summary>
/// A bind engine supports custom data binding.
/// </summary>
/// <remarks>
/// It exports two methods for data binding:
/// 1.SetPropertyBinding
/// 2.ClearPropertyBinding
/// The binding engine use weak reference to hold the dependent, that means if u miss to clear data binding,
/// the dependent will not leak memory.
/// </remarks>
/// <author>
/// yohan zhou
///http://www.cnblogs.com/zhouyongh
/// </author>
public class BindingEngine
{
#region Field
private static Dictionary<WeakEntry, Delegate> _expressionSources = new Dictionary<WeakEntry, Delegate>();
#endregion
/// <summary>
/// Sets the property binding.
/// </summary>
/// <param name="source">The source.</param>
/// <param name="target">The target.</param>
/// <param name="sourceProp">The source prop.</param>
/// <param name="targetProp">The target prop.</param>
/// <param name="converter">The converter.</param>
/// <param name="parameter">The converter parameter.</param>
public static void SetPropertyBinding(Object source, INotifyPropertyChanged target, string sourceProp, string targetProp, IDataConverter converter = null, object parameter = null)
{
SetPropertyBinding(source, target, sourceProp, targetProp, true, converter, parameter);
}
/// <summary>
/// Sets the property binding.
/// </summary>
/// <param name="source">The source.</param>
/// <param name="target">The target.</param>
/// <param name="sourceProp">The source prop.</param>
/// <param name="targetProp">The target prop.</param>
/// <param name="notify">if set to <c>true</c> update immediately.</param>
/// <param name="converter">The converter.</param>
/// <param name="parameter">The converter parameter.</param>
public static void SetPropertyBinding(Object source, INotifyPropertyChanged target, string sourceProp, string targetProp, bool notify, IDataConverter converter = null, object parameter = null)
{
WeakEntry entry = new WeakEntry(source.GetType(), target.GetType(), sourceProp, targetProp);
Delegate setAction = GetExpressionAction(entry, source, true, converter);
WeakSource wSource = WeakSource.Register(source, target, setAction, sourceProp, targetProp, converter, parameter);
if (notify)
{
wSource.NotifyPropertyChanged(target, targetProp);
}
}
/// <summary>
/// Clears the property binding.
/// </summary>
/// <param name="source">The source.</param>
/// <param name="target">The target.</param>
/// <param name="sourceProp">The source prop.</param>
/// <param name="targetProp">The target prop.</param>
public static void ClearPropertyBinding(Object source, INotifyPropertyChanged target, string sourceProp, string targetProp)
{
WeakSource.UnRegister(source, target, sourceProp, targetProp);
}
/// <summary>
/// Gets the expression action.
/// </summary>
/// <param name="entry">The entry.</param>
/// <param name="source">The source.</param>
/// <param name="createNew">if set to <c>true</c> [create new].</param>
/// <param name="converter">The converter.</param>
/// <returns></returns>
private static Delegate GetExpressionAction(WeakEntry entry, object source, bool createNew, IDataConverter converter = null)
{
Delegate action = null;
if (_expressionSources.ContainsKey(entry))
{
action = _expressionSources[entry];
}
else if (createNew)
{
///// Code of the below Expression Tree ////////////////////////////////
//if (converter != null)
//{
// target.Property = converter.Convert(source.Property, parameter);
//}
//else
//{
// if (target.Property.GetType() == source.Property.GetType())
// {
// target.Property = source.Property;
// }
// else
// {
// throw new InvalidOperationException("The property type between binding source and target does not match, please use IDataConverter to do custom convert.");
// }
//}
//////////////////////////////////////////////////////////////////////////
//Set Property
var prop = entry.SourceType.GetProperty(entry.SourceProp);
var paraObj = Expression.Parameter(entry.SourceType);
//Get Property
var targetProperty = entry.TargetType.GetProperty(entry.TargetProp);
var paraTarget = Expression.Parameter(entry.TargetType);
var getter = Expression.Property(paraTarget, targetProperty);
//Combine
Expression boy;
var paraConvert = Expression.Variable(typeof(IDataConverter));
var paraParameter = Expression.Variable(typeof(object));
boy = Expression.IfThenElse(
Expression.NotEqual(paraConvert, Expression.Constant(null)),
Expression.Call(paraObj, prop.GetSetMethod(), Expression.Convert(Expression.Call(paraConvert, typeof(IDataConverter).GetMethod("Convert"),
Expression.Convert(getter, typeof(object)), Expression.Convert(paraParameter, typeof(object))), prop.PropertyType)),
Expression.IfThenElse(
Expression.Equal(Expression.Constant(prop.PropertyType, typeof(Type)), Expression.Constant(getter.Type, typeof(Type))),
Expression.Call(paraObj, prop.GetSetMethod(), Expression.Convert(Expression.Convert(getter, typeof(object)), prop.PropertyType)),
Expression.Throw(Expression.Constant(new InvalidOperationException(
"The property type between binding source and target does not match, please use IDataConverter to do custom convert.")))));
action = Expression.Lambda(boy, paraObj, paraTarget, paraConvert, paraParameter).Compile();
_expressionSources.Add(entry, action);
}
return action;
}
private struct WeakEntry
{
public Type SourceType;
public Type TargetType;
public string SourceProp;
public string TargetProp;
/// <summary>
/// Initializes a new instance of the <see cref="WeakEntry"/> struct.
/// </summary>
/// <param name="sourceType">Type of the source.</param>
/// <param name="targetType">Type of the target.</param>
/// <param name="sourceProp">The source prop.</param>
/// <param name="targetProp">The target prop.</param>
public WeakEntry(Type sourceType, Type targetType, string sourceProp, string targetProp)
{
SourceType = sourceType;
TargetType = targetType;
SourceProp = sourceProp;
TargetProp = targetProp;
}
/// <summary>
/// Returns the hash code for this instance.
/// </summary>
/// <returns>
/// A 32-bit signed integer that is the hash code for this instance.
/// </returns>
public override int GetHashCode()
{
return SourceType.GetHashCode() ^ TargetType.GetHashCode() ^ SourceProp.GetHashCode() ^ TargetProp.GetHashCode();
}
/// <summary>
/// Indicates whether this instance and a specified object are equal.
/// </summary>
/// <param name="obj">Another object to compare to.</param>
/// <returns>
/// true if <paramref name="obj"/> and this instance are the same type and represent the same value; otherwise, false.
/// </returns>
public override bool Equals(object obj)
{
WeakEntry entry = (WeakEntry)obj;
return ((this.SourceType == entry.SourceType) && (this.TargetType == entry.TargetType) &&
(this.SourceProp == entry.SourceProp) && (this.TargetProp == entry.TargetProp));
}
/// <summary>
/// Implements the operator ==.
/// </summary>
/// <param name="obj1">The obj1.</param>
/// <param name="obj2">The obj2.</param>
/// <returns>The result of the operator.</returns>
public static bool operator ==(WeakEntry obj1, WeakEntry obj2)
{
return obj1.Equals(obj2);
}
/// <summary>
/// Implements the operator !=.
/// </summary>
/// <param name="obj1">The obj1.</param>
/// <param name="obj2">The obj2.</param>
/// <returns>The result of the operator.</returns>
public static bool operator !=(WeakEntry obj1, WeakEntry obj2)
{
return !(obj1 == obj2);
}
}
private class WeakAction
{
public string SourceProp;
public Delegate Action;
public IDataConverter Converter;
public object Parameter;
public WeakAction(string sourceProp, Delegate action, IDataConverter converter, object parameter)
{
System.Diagnostics.Debug.Assert(action != null);
SourceProp = sourceProp;
Action = action;
Converter = converter;
Parameter = parameter;
}
}
private class WeakSource : WeakReference
{
private static Dictionary<int, WeakSource> _weakSources = new Dictionary<int, WeakSource>();
public Dictionary<int, Dictionary<string, IList<WeakAction>>> Targets = new Dictionary<int, Dictionary<string, IList<WeakAction>>>();
/// <summary>
/// Registers the specified source.
/// </summary>
/// <param name="source">The source.</param>
/// <param name="target">The target.</param>
/// <param name="action">The action.</param>
/// <param name="sourceProp">The source prop.</param>
/// <param name="targetProp">The target prop.</param>
/// <param name="converter">The converter.</param>
/// <param name="parameter">The converter parameter.</param>
/// <returns></returns>
public static WeakSource Register(Object source, INotifyPropertyChanged target, Delegate action, string sourceProp, string targetProp, IDataConverter converter = null, object parameter = null)
{
WeakSource wSource = _weakSources.ContainsKey(source.GetHashCode()) ? _weakSources[source.GetHashCode()] : null;
if (wSource == null)
{
wSource = new WeakSource(source);
_weakSources.Add(source.GetHashCode(), wSource);
}
Dictionary<string, IList<WeakAction>> targetActions;
int id = target.GetHashCode();
if (wSource.Targets.ContainsKey(id))
{
targetActions = wSource.Targets[id];
}
else
{
targetActions = new Dictionary<string, IList<WeakAction>>();
wSource.Targets.Add(id, targetActions);
target.PropertyChanged += new PropertyChangedEventHandler(wSource.HandlePropertyChanged);
}
WeakAction wAction = new WeakAction(sourceProp, action, converter, parameter);
if (targetActions.ContainsKey(targetProp))
{
var actions = targetActions[targetProp];
var oldAction = actions.FirstOrDefault(item => string.Equals(item.SourceProp, sourceProp));
if (oldAction != null)
{
actions.Remove(oldAction);
}
actions.Add(wAction);
}
else
{
targetActions.Add(targetProp, new List<WeakAction>() { wAction });
}
return wSource;
}
/// <summary>
/// Unregister the specified source.
/// </summary>
/// <param name="source">The source.</param>
/// <param name="target">The target.</param>
/// <param name="targetProp">The target prop.</param>
public static void UnRegister(Object source, INotifyPropertyChanged target, string sourceProp, string targetProp)
{
WeakSource wSource = _weakSources.ContainsKey(source.GetHashCode()) ? _weakSources[source.GetHashCode()] : null;
int targetId = target.GetHashCode();
if (wSource != null && wSource.Targets.ContainsKey(targetId))
{
Dictionary<string, IList<WeakAction>> actions = wSource.Targets[targetId];
if (actions.ContainsKey(targetProp))
{
var targetActions = actions[targetProp];
var action = targetActions.FirstOrDefault(item => string.Equals(item.SourceProp, sourceProp));
if (action != null)
{
targetActions.Remove(action);
}
if (targetActions.Count == 0)
{
actions.Remove(targetProp);
}
if (actions.Count == 0)
{
wSource.Targets.Remove(targetId);
}
}
}
}
/// <summary>
/// Initializes a new instance of the <see cref="WeakSource"/> class.
/// </summary>
/// <param name="source">The source.</param>
private WeakSource(Object source)
: base(source)
{
}
/// <summary>
/// Notifies the property changed.
/// </summary>
/// <param name="target">The target.</param>
/// <param name="targetProp">The target prop.</param>
public void NotifyPropertyChanged(INotifyPropertyChanged target, string targetProp)
{
int id = target.GetHashCode();
if (!Targets.ContainsKey(id))
{
return;
}
if (Targets[id].ContainsKey(targetProp))
{
foreach (var action in Targets[id][targetProp])
{
action.Action.DynamicInvoke(this.Target, target, action.Converter, action.Parameter);
}
}
}
/// <summary>
/// Handles the property changed.
/// </summary>
/// <param name="sender">The sender.</param>
/// <param name="args">The <see cref="System.ComponentModel.PropertyChangedEventArgs"/> instance containing the event data.</param>
public void HandlePropertyChanged(object sender, PropertyChangedEventArgs args)
{
INotifyPropertyChanged target = sender as INotifyPropertyChanged;
if (target == null)
{
throw new NotSupportedException("WeakSource can only work on INotifyPropertyChanged");
}
if (IsAlive)
{
NotifyPropertyChanged(target, args.PropertyName);
}
else
{
target.PropertyChanged -= new PropertyChangedEventHandler(HandlePropertyChanged);
Targets.Remove(target.GetHashCode());
}
}
}
}
public interface IDataConverter
{
object Convert(object value, object parameter);
}
}
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