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。

1
public class SimpleData : ViewModelBase 

2
{ 

3
    private string _text; 

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    private int _column, _row; 

5
 
6
    public string Text { get { return _text; } set { _text = value; OnPropertyChanged("Text"); } } 

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    public int Column { get { return _column; } set { _column = value; OnPropertyChanged("Column"); } } 

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    public int Row { get { return _row; } set { _row = value; OnPropertyChanged("Row"); } } 

9
}

前台代码：

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<Grid x:Name="LayoutRoot" Background="White"> 

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    <ItemsControl ItemsSource="{Binding}"> 

03
        <ItemsControl.ItemTemplate> 

04
            <DataTemplate> 

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                <TextBox Text="{Binding Text}"

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                         Foreground="Green"

07
                         Grid.Row="{Binding Row}"

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                         Grid.Column="{Binding Column}"

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                         Height="30" Width="150"

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                         /> 

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            </DataTemplate> 

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        </ItemsControl.ItemTemplate> 

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        <ItemsControl.ItemsPanel> 

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            <ItemsPanelTemplate> 

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                <Grid ShowGridLines="True"> 

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                    <Grid.RowDefinitions> 

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                        <RowDefinition/> 

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                        <RowDefinition/> 

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                        <RowDefinition/> 

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                    </Grid.RowDefinitions> 

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                    <Grid.ColumnDefinitions> 

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                        <ColumnDefinition/> 

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                        <ColumnDefinition/> 

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                    </Grid.ColumnDefinitions> 

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                </Grid> 

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            </ItemsPanelTemplate> 

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        </ItemsControl.ItemsPanel> 

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    </ItemsControl> 

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</Grid>

后台代码：

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public partial class MainPage : UserControl 

02
{ 

03
    public MainPage() 

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    { 

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        InitializeComponent(); 

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        this.DataContext = new SimpleData[] 

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        { 

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            new SimpleData{ Text = "111111", Column = 0, Row = 0 }, 

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            new SimpleData{ Text = "222222", Column = 1, Row = 1 },  

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            new SimpleData{ Text = "333333", Column = 0, Row = 2 },  

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        }; 

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    } 

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}

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：

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<ItemsControl.ItemContainerStyle> 

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    <Style> 

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

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

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    </Style> 

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</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。

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using System; 

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using System.Collections.Generic; 

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using System.Globalization; 

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using System.Linq; 

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using System.Reflection; 

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using System.Windows; 

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using System.Windows.Controls; 

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using System.Windows.Data; 

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using System.Windows.Media; 

010
  
011
namespace Delay 

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{ 

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    public class UpUp : DependencyObject 

014
    { 

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        // Using a DependencyProperty as the backing store for Up.  This enables animation, styling, binding, etc... 

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        public static readonly DependencyProperty UpProperty = 

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            DependencyProperty.RegisterAttached("Up", typeof(string), typeof(UpUp), new PropertyMetadata(string.Empty)); 

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019
        public static void SetUp(FrameworkElement element, string value) 

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        { 

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            HanderClosure hander = element.GetValue(UpProperty) as HanderClosure; 

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            if (hander == null) 

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            { 

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                hander = new HanderClosure(element, value); 

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                element.SetValue(UpProperty, value); 

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                element.LayoutUpdated += new EventHandler(hander.element_LayoutUpdated); 

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            } 

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        } 

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        public static string GetUp(FrameworkElement element) 

030
        { 

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            HanderClosure hander = element.GetValue(UpProperty) as HanderClosure; 

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            if (hander == null) 

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                return null; 

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            else

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                return hander.OrgParamenter; 

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        } 

037
  
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        private class HanderClosure 

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        { 

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            private FrameworkElement _elem = null; 

041
            private string[] propertys = null; 

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            private int _level; 

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            private UpMode _mode; 

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            private string _orgParamenter; 

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            public string OrgParamenter { get { return _orgParamenter; } } 

047
  
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            public HanderClosure(FrameworkElement element, string parameter) 

049
            { 

050
                if (element == null) 

051
                    throw new ArgumentNullException("element"); 

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                if (parameter == null) 

053
                    throw new ArgumentNullException("parameter"); 

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                _elem = element; 

055
                _level = 1; 

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                _mode = UpMode.Copy; 

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                _orgParamenter = parameter; 

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059
                string[] array = parameter.Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries); 

060
                if (array.Length == 0) 

061
                    throw new ArgumentException("parameter"); 

062
                propertys = array[0].Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries); 

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                if (array.Length > 1) 

064
                { 

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                    int num; 

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                    if (int.TryParse(array[1].Trim(), out num)) 

067
                    { 

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                        _level = num; 

069
                    } 

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                } 

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                if (array.Length > 2) 

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                { 

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                    UpMode mode; 

074
                    if (Enum.TryParse<UpMode>(array[2].Trim(), true, out mode)) 

075
                    { 

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                        _mode = mode; 

077
                    } 

078
                } 

079
            } 

080
  
081
            public void element_LayoutUpdated(object sender, EventArgs e) 

082
            { 

083
                FrameworkElement parent = _elem; 

084
                for (int i = 0; i < _level && parent != null; i++) 

085
                { 

086
                    parent = VisualTreeHelper.GetParent(parent) as FrameworkElement; 

087
                } 

088
                if (parent == null) 

089
                    return; 

090
  
091
                foreach (string property in propertys) 

092
                { 

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                    Apply(_elem, parent, property.Trim()); 

094
                } 

095
            } 

096
  
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            // Copyright (C) Microsoft Corporation. All Rights Reserved. 

098
            // This code released under the terms of the Microsoft Public License 

099
            // (Ms-PL, http://opensource.org/licenses/ms-pl.html). 

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            private void Apply(FrameworkElement element1, FrameworkElement element2, string property) 

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            { 

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                var array = property.Split('.'); 

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                if (array.Length != 2) 

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                    throw new ArgumentException("property"); 

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                string typeName = array[0].Trim(); 

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                string propertyName = array[1].Trim(); 

107
  
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                Type type = null; 

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                foreach (var assembly in AssembliesToSearch) 

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                { 

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                    // Match on short or full name 

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                    type = assembly.GetTypes() 

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                       .Where(t => (t.FullName == typeName) || (t.Name == typeName)) 

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                       .FirstOrDefault(); 

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                    if (type != null) 

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                        break; 

117
                } 

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                if (null == type) 

119
                { 

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                    // Unable to find the requested type anywhere 

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                    throw new ArgumentException( 

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                        string.Format( 

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                            CultureInfo.CurrentCulture, 

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                            "Unable to access type \"{0}\". Try using an assembly qualified type name.", 

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                            typeName)); 

126
                } 

127
  
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                // Get the DependencyProperty for which to set the Binding 

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                DependencyProperty dp = null; 

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                var field = type.GetField( 

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                    propertyName + "Property", 

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                    BindingFlags.FlattenHierarchy | BindingFlags.Public | BindingFlags.Static); 

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                if (null != field) 

134
                { 

135
                    dp = field.GetValue(null) as DependencyProperty; 

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                } 

137
                if (null == dp) 

138
                { 

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                    // Unable to find the requsted property 

140
                    throw new ArgumentException( 

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                        string.Format( 

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                            CultureInfo.CurrentCulture, 

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                            "Unable to access DependencyProperty \"{0}\" on type \"{1}\".", 

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                            propertyName, 

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                            type.Name)); 

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                } 

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                BindingExpression binding = element1.GetBindingExpression(dp); 

149
                object value = element1.GetValue(dp); 

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                if (binding != null) 

151
                { 

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                    element2.SetBinding(dp, binding.ParentBinding); 

153
                } 

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                else if (value != null) 

155
                { 

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                    element2.SetValue(dp, value); 

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                } 

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                if (_mode == UpMode.Move) 

159
                    element1.ClearValue(dp); 

160
            } 

161
  
162
            // Copyright (C) Microsoft Corporation. All Rights Reserved. 

163
            // This code released under the terms of the Microsoft Public License 

164
            // (Ms-PL, http://opensource.org/licenses/ms-pl.html). 

165
            /// <summary> 

166
            /// Gets a sequence of assemblies to search for the provided type name. 

167
            /// </summary> 

168
            private IEnumerable<Assembly> AssembliesToSearch 

169
            { 

170
                get

171
                { 

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                    // Start with the System.Windows assembly (home of all core controls) 

173
                    yield return typeof(Control).Assembly; 

174
  
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#if SILVERLIGHT && !WINDOWS_PHONE 

176
                    // Fall back by trying each of the assemblies in the Deployment's Parts list 

177
                    foreach (var part in Deployment.Current.Parts) 

178
                    { 

179
                        var streamResourceInfo = Application.GetResourceStream( 

180
                            new Uri(part.Source, UriKind.Relative)); 

181
                        using (var stream = streamResourceInfo.Stream) 

182
                        { 

183
                            yield return part.Load(stream); 

184
                        } 

185
                    } 

186
#endif 

187
                } 

188
            } 

189
        } 

190
  
191
        private enum UpMode 

192
        { 

193
            Move, 

194
            Copy, 

195
        } 

196
    } 

197
}

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：

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<UserControl x:Class="TestValueBindingInItemTemplate.MainPage"

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    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

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    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

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    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

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    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

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    xmlns:delay="clr-namespace:Delay"

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    mc:Ignorable="d"

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    d:DesignHeight="300" d:DesignWidth="400"> 

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10
    <Grid x:Name="LayoutRoot" Background="White"> 

11
        <ItemsControl ItemsSource="{Binding}"> 

12
            <ItemsControl.ItemTemplate> 

13
                <DataTemplate> 

14
                    <TextBox Text="{Binding Text}"

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                             Foreground="Green"

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                             Grid.Row="{Binding Row}"

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                             Grid.Column="{Binding Column}"

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                             Height="30" Width="150"

19
                             delay:UpUp.Up="Grid.Row,Grid.Column"

20
                             /> 

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                </DataTemplate> 

22
            </ItemsControl.ItemTemplate> 

23
            <ItemsControl.ItemsPanel> 

24
                <ItemsPanelTemplate> 

25
                    <Grid ShowGridLines="True"> 

26
                        <Grid.RowDefinitions> 

27
                            <RowDefinition/> 

28
                            <RowDefinition/> 

29
                            <RowDefinition/> 

30
                        </Grid.RowDefinitions> 

31
                        <Grid.ColumnDefinitions> 

32
                            <ColumnDefinition/> 

33
                            <ColumnDefinition/> 

34
                        </Grid.ColumnDefinitions> 

35
                    </Grid> 

36
                </ItemsPanelTemplate> 

37
            </ItemsControl.ItemsPanel> 

38
        </ItemsControl> 

39
    </Grid> 

40
</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。

posted on 2011-09-14 08:49 SplendidMe 阅读(1075) 评论(0) 收藏举报