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POSilverlight UserControl Custom Property Binding
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  1. POSilverlight UserControl Custom Property Binding
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    copied!<p>What is the proper way to implement Custom Properties in Silverlight UserControls?</p> <p>Every "Page" in Silverlight is technically a UserControl (they are derived from the UserControl class). When I say UserControl here, I mean a Custom UserControl that will be used inside many different pages in many different scenarios (similar to an ASP.NET UserControl).</p> <p>I would like the Custom UserControl to support Binding and not rely on the Name of the Property it is binding to, to always be the same. Instead, I would like the UserControl itself to have a property that the Controls inside the UserControl bind to, and the ViewModels outside the UserControl also bind to. (please see the example below)</p> <p>Binding within the UserControl works, Binding within the MainPage works, The Binding I set up between the MainPage and the UserControl does not work. Specifically this line:</p> <pre class="lang-xml prettyprint-override"><code>&lt;myUserControls:MyCustomUserControl x:Name="MyCustomControl2" SelectedText="{Binding MainPageSelectedText, Mode=TwoWay}" Width="200" Height="50" /&gt; </code></pre> <p>example output:<br> <img src="https://i690.photobucket.com/albums/vv264/cfalc0n/SilverlightUserControlCustomPropert.png" alt="alt text"></p> <p>MainPage.xaml</p> <pre class="lang-xml prettyprint-override"><code>&lt;UserControl x:Class="SilverlightCustomUserControl.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:myUserControls="clr-namespace:SilverlightCustomUserControl" mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480" DataContext="{Binding RelativeSource={RelativeSource Self}}"&gt; &lt;Canvas x:Name="LayoutRoot"&gt; &lt;StackPanel Orientation="Vertical"&gt; &lt;TextBlock Text="UserControl Binding:" Width="200"&gt;&lt;/TextBlock&gt; &lt;myUserControls:MyCustomUserControl x:Name="MyCustomControl2" SelectedText="{Binding MainPageSelectedText, Mode=TwoWay}" Width="200" Height="50" /&gt; &lt;TextBlock Text="MainPage Binding:" Width="200"&gt;&lt;/TextBlock&gt; &lt;TextBox Text="{Binding MainPageSelectedText, Mode=TwoWay}" Width="200"&gt;&lt;/TextBox&gt; &lt;Border BorderBrush="Black" BorderThickness="1"&gt; &lt;TextBlock Text="{Binding MainPageSelectedText}" Width="200" Height="24"&gt;&lt;/TextBlock&gt; &lt;/Border&gt; &lt;/StackPanel&gt; &lt;/Canvas&gt; &lt;/UserControl&gt; </code></pre> <p>MainPage.xaml.cs</p> <pre><code>namespace SilverlightCustomUserControl { public partial class MainPage : UserControl, INotifyPropertyChanged { //NOTE: would probably be in a ViewModel public string MainPageSelectedText { get { return _MainPageSelectedText; } set { string myValue = value ?? String.Empty; if (_MainPageSelectedText != myValue) { _MainPageSelectedText = value; OnPropertyChanged("MainPageSelectedText"); } } } private string _MainPageSelectedText; public MainPage() { InitializeComponent(); } #region INotifyPropertyChanged Members public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged(string name) { PropertyChangedEventHandler ph = this.PropertyChanged; if (ph != null) ph(this, new PropertyChangedEventArgs(name)); } #endregion } } </code></pre> <p>MyCustomUserControl.xaml</p> <pre class="lang-xml prettyprint-override"><code>&lt;UserControl x:Class="SilverlightCustomUserControl.MyCustomUserControl" 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" DataContext="{Binding RelativeSource={RelativeSource Self}}"&gt; &lt;Grid&gt; &lt;StackPanel&gt; &lt;TextBox Text="{Binding SelectedText, Mode=TwoWay}" /&gt; &lt;Border BorderBrush="Black" BorderThickness="1"&gt; &lt;TextBlock Text="{Binding SelectedText}" Height="24"&gt;&lt;/TextBlock&gt; &lt;/Border&gt; &lt;/StackPanel&gt; &lt;/Grid&gt; &lt;/UserControl&gt; </code></pre> <p>MyCustomUserControl.xaml.cs</p> <pre><code>namespace SilverlightCustomUserControl { public partial class MyCustomUserControl : UserControl { public string SelectedText { get { return (string)GetValue(SelectedTextProperty); } set { SetValue(SelectedTextProperty, value); } } public static readonly DependencyProperty SelectedTextProperty = DependencyProperty.Register("SelectedText", typeof(string), typeof(MyCustomUserControl), new PropertyMetadata("", SelectedText_PropertyChangedCallback)); public MyCustomUserControl() { InitializeComponent(); } private static void SelectedText_PropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e) { //empty } } } </code></pre> <p>References (how I got this far): </p> <p>use DependencyPropertys: <a href="http://geekswithblogs.net/thibbard/archive/2008/04/22/wpf-custom-control-dependency-property-gotcha.aspx" rel="nofollow noreferrer">http://geekswithblogs.net/thibbard/archive/2008/04/22/wpf-custom-control-dependency-property-gotcha.aspx</a></p> <p>use DependencyPropertys, add x:Name to your UserControl - add Binding with ElementName, set Custom property again in the PropertyChangedCallback method: <a href="https://stackoverflow.com/questions/845564/setting-custom-properties-in-usercontrol-via-databinding">Setting Custom Properties in UserControl via DataBinding</a></p> <p>don't use custom properties, rely on underlying datacontext names (I do not like this solution): <a href="https://stackoverflow.com/questions/1145435/wpf-trouble-using-dependency-properties-in-a-usercontrol">wpf trouble using dependency properties in a UserControl</a></p>
 

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