【Silverlight】解决DataTemplate绑定附加属性

    本文 Silverlight 版本：4.0。

    首先定义数据类型，此文始终使用此定义类型。

    public class SimpleData : ViewModelBase{private string _text;private int _column, _row;public string Text { get { return _text; } set { _text = value; OnPropertyChanged("Text"); } }public int Column { get { return _column; } set { _column = value; OnPropertyChanged("Column"); } }public int Row { get { return _row; } set { _row = value; OnPropertyChanged("Row"); } }}

    前台代码：

    <Grid x:Name="LayoutRoot" Background="White"><ItemsControl ItemsSource="{Binding}"><ItemsControl.ItemTemplate><DataTemplate><TextBox Text="{Binding Text}"Foreground="Green"Grid.Row="{Binding Row}"Grid.Column="{Binding Column}"Height="30" Width="150"/></DataTemplate></ItemsControl.ItemTemplate><ItemsControl.ItemsPanel><ItemsPanelTemplate><Grid ShowGridLines="True"><Grid.RowDefinitions><RowDefinition/><RowDefinition/><RowDefinition/></Grid.RowDefinitions><Grid.ColumnDefinitions><ColumnDefinition/><ColumnDefinition/></Grid.ColumnDefinitions></Grid></ItemsPanelTemplate></ItemsControl.ItemsPanel></ItemsControl></Grid>

    后台代码：

    public partial class MainPage : UserControl{public MainPage(){InitializeComponent();this.DataContext = new SimpleData[]{new SimpleData{ Text = "111111", Column = 0, Row = 0 },new SimpleData{ Text = "222222", Column = 1, Row = 1 }, new SimpleData{ Text = "333333", Column = 0, Row = 2 }, };}}

    可以看出这段代码的本意是通过绑定的方式设置，在 ItemsControl 里面显示 3 个 TextBox，同时指定了相应在 Grid 的行和列。

    但是，你懂的！

    这样的代码肯定是不能正确运行。特别是在Silverlight。

    如果这是在 WPF 环境，很庆幸你还可以用 ItemContainerStyle 搞定：

            <ItemsControl.ItemContainerStyle><Style><Setter Property="Grid.Row" Value="{Binding Row, Mode=OneWay}"/><Setter Property="Grid.Column" Value="{Binding Column, Mode=OneWay}"/></Style></ItemsControl.ItemContainerStyle>

    只可惜这是在 Silverlight 环境。我们只能够想别的办法了。

 

    为什么不可以？拿出 Silverlight Spy 或者 Snoop 查看相应的 VisualTree。可以看到在 TextBox 外面还套了一个 ContextPresenter。

    于是我们可以想到，能不能设置 ContextPresenter 的 Grid.Row 和 Grid.Colume 达到控制行列的目的？

    于是我们得到下面的思路，使用附加属性把相应的绑定关系提升。

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Reflection;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Media;namespace Delay
{public class UpUp : DependencyObject{// Using a DependencyProperty as the backing store for Up.  This enables animation, styling, binding, etc...public static readonly DependencyProperty UpProperty =DependencyProperty.RegisterAttached("Up", typeof(string), typeof(UpUp), new PropertyMetadata(string.Empty));public static void SetUp(FrameworkElement element, string value){HanderClosure hander = element.GetValue(UpProperty) as HanderClosure;if (hander == null){hander = new HanderClosure(element, value);element.SetValue(UpProperty, value);element.LayoutUpdated += new EventHandler(hander.element_LayoutUpdated);}}public static string GetUp(FrameworkElement element){HanderClosure hander = element.GetValue(UpProperty) as HanderClosure;if (hander == null)return null;elsereturn hander.OrgParamenter;}private class HanderClosure{private FrameworkElement _elem = null;private string[] propertys = null;private int _level;private UpMode _mode;private string _orgParamenter;public string OrgParamenter { get { return _orgParamenter; } }public HanderClosure(FrameworkElement element, string parameter){if (element == null)throw new ArgumentNullException("element");if (parameter == null)throw new ArgumentNullException("parameter");_elem = element;_level = 1;_mode = UpMode.Copy;_orgParamenter = parameter;string[] array = parameter.Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries);if (array.Length == 0)throw new ArgumentException("parameter");propertys = array[0].Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries);if (array.Length > 1){int num;if (int.TryParse(array[1].Trim(), out num)){_level = num;}}if (array.Length > 2){UpMode mode;if (Enum.TryParse<UpMode>(array[2].Trim(), true, out mode)){_mode = mode;}}}public void element_LayoutUpdated(object sender, EventArgs e){FrameworkElement parent = _elem;for (int i = 0; i < _level && parent != null; i++){parent = VisualTreeHelper.GetParent(parent) as FrameworkElement;}if (parent == null)return;foreach (string property in propertys){Apply(_elem, parent, property.Trim());}}// Copyright (C) Microsoft Corporation. All Rights Reserved.// This code released under the terms of the Microsoft Public License// (Ms-PL, http://opensource.org/licenses/ms-pl.html).private void Apply(FrameworkElement element1, FrameworkElement element2, string property){var array = property.Split('.');if (array.Length != 2)throw new ArgumentException("property");string typeName = array[0].Trim();string propertyName = array[1].Trim();Type type = null;foreach (var assembly in AssembliesToSearch){// Match on short or full nametype = assembly.GetTypes().Where(t => (t.FullName == typeName) || (t.Name == typeName)).FirstOrDefault();if (type != null)break;}if (null == type){// Unable to find the requested type anywherethrow new ArgumentException(string.Format(CultureInfo.CurrentCulture,"Unable to access type \"{0}\". Try using an assembly qualified type name.",typeName));}// Get the DependencyProperty for which to set the BindingDependencyProperty dp = null;var field = type.GetField(propertyName + "Property",BindingFlags.FlattenHierarchy | BindingFlags.Public | BindingFlags.Static);if (null != field){dp = field.GetValue(null) as DependencyProperty;}if (null == dp){// Unable to find the requsted propertythrow new ArgumentException(string.Format(CultureInfo.CurrentCulture,"Unable to access DependencyProperty \"{0}\" on type \"{1}\".",propertyName,type.Name));}BindingExpression binding = element1.GetBindingExpression(dp);object value = element1.GetValue(dp);if (binding != null){element2.SetBinding(dp, binding.ParentBinding);}else if (value != null){element2.SetValue(dp, value);}if (_mode == UpMode.Move)element1.ClearValue(dp);}// Copyright (C) Microsoft Corporation. All Rights Reserved.// This code released under the terms of the Microsoft Public License// (Ms-PL, http://opensource.org/licenses/ms-pl.html)./// <summary>/// Gets a sequence of assemblies to search for the provided type name./// </summary>private IEnumerable<Assembly> AssembliesToSearch{get{// Start with the System.Windows assembly (home of all core controls)yield return typeof(Control).Assembly;#if SILVERLIGHT && !WINDOWS_PHONE// Fall back by trying each of the assemblies in the Deployment's Parts listforeach (var part in Deployment.Current.Parts){var streamResourceInfo = Application.GetResourceStream(new Uri(part.Source, UriKind.Relative));using (var stream = streamResourceInfo.Stream){yield return part.Load(stream);}}
#endif}}}private enum UpMode{Move,Copy,}}
}

    如何使用？使用非常简单！

    在你的项目中增加 UpUp 之后，在需要提升绑定级别的 Page 的 Xaml 中引入命名空间 xmlns:delay="clr-namespace:Delay"。然后在需要提升绑定级别的控件中加入属性 delay:UpUp.Up="Grid.Row,Grid.Column"。得到完整的前台代码如下：

<UserControl x:Class="TestValueBindingInItemTemplate.MainPage"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"xmlns:delay="clr-namespace:Delay"mc:Ignorable="d"d:DesignHeight="300" d:DesignWidth="400"><Grid x:Name="LayoutRoot" Background="White"><ItemsControl ItemsSource="{Binding}"><ItemsControl.ItemTemplate><DataTemplate><TextBox Text="{Binding Text}"Foreground="Green"Grid.Row="{Binding Row}"Grid.Column="{Binding Column}"Height="30" Width="150"delay:UpUp.Up="Grid.Row,Grid.Column"/></DataTemplate></ItemsControl.ItemTemplate><ItemsControl.ItemsPanel><ItemsPanelTemplate><Grid ShowGridLines="True"><Grid.RowDefinitions><RowDefinition/><RowDefinition/><RowDefinition/></Grid.RowDefinitions><Grid.ColumnDefinitions><ColumnDefinition/><ColumnDefinition/></Grid.ColumnDefinitions></Grid></ItemsPanelTemplate></ItemsControl.ItemsPanel></ItemsControl></Grid>
</UserControl>

    UpUp.Up 应该如何填写？实际上 UpUp.Up 属性有具体的语法格式：

 

UpUp.Up="Type.Property[,Type.Property ...][;Level[;Move|Copy]]"

 

    其中

    Type.Property 是需要提升绑定关系的属性名称，可以用逗号把多个属性名称隔开。

    Level 是整数，表示需要提升的层次。在 VisualTree 中向上一层为一个层次。

    Move|Copy 是枚举类型，表示提升之后保留原来的绑定关系。

    例如：delay:UpUp.Up="Grid.Row,Grid.Column;1;Copy"

 

    有了 UpUp 之后，对于类似的绑定问题可以轻而易举的完成了！

 

PS：WPF 也可以用此方法实现，但是有细节方面的差异。

1、不能够使用SetXXX GetXXX，要使用 XXX 属性。

2、需要注册 PropertyChangedCallback 事件，并将相关注册 Hander 部分放置到此方法内。

 

本文完整代码在此下载：http://files.cnblogs.com/Aimeast/SLTestValueBindingInItemTemplate.zip