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POWPF: how to find an element in a datatemplate from an itemscontrol
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  1. POWPF: how to find an element in a datatemplate from an itemscontrol
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    copied!<p>I have the following problem: the application is using the custom itemscontrol called ToolBox. The elements of a toolbox are called toolboxitems and are custom contentcontrol. Now, the toolbox stores a number of images that are retrieved from a database and displayed. For that I use a datatemplate inside the toolbox control. However, when I try to drag and drop the elements, I don't get the image object but the database component. I thought that I should then traverse the structure to find the Image element. here's the code:</p> <p>Toolbox:</p> <pre><code>public class Toolbox : ItemsControl { private Size defaultItemSize = new Size(65, 65); public Size DefaultItemSize { get { return this.defaultItemSize; } set { this.defaultItemSize = value; } } protected override DependencyObject GetContainerForItemOverride() { return new ToolboxItem(); } protected override bool IsItemItsOwnContainerOverride(object item) { return (item is ToolboxItem); } } </code></pre> <p>ToolBoxItem:</p> <pre><code>public class ToolboxItem : ContentControl { private Point? dragStartPoint = null; static ToolboxItem() { FrameworkElement.DefaultStyleKeyProperty.OverrideMetadata(typeof(ToolboxItem), new FrameworkPropertyMetadata(typeof(ToolboxItem))); } protected override void OnPreviewMouseDown(MouseButtonEventArgs e) { base.OnPreviewMouseDown(e); this.dragStartPoint = new Point?(e.GetPosition(this)); } public String url { get; private set; } protected override void OnMouseMove(MouseEventArgs e) { base.OnMouseMove(e); if (e.LeftButton != MouseButtonState.Pressed) { this.dragStartPoint = null; } if (this.dragStartPoint.HasValue) { Point position = e.GetPosition(this); if ((SystemParameters.MinimumHorizontalDragDistance &lt;= Math.Abs((double)(position.X - this.dragStartPoint.Value.X))) || (SystemParameters.MinimumVerticalDragDistance &lt;= Math.Abs((double)(position.Y - this.dragStartPoint.Value.Y)))) { string xamlString = XamlWriter.Save(this.Content); MessageBoxResult result = MessageBox.Show(xamlString); DataObject dataObject = new DataObject("DESIGNER_ITEM", xamlString); if (dataObject != null) { DragDrop.DoDragDrop(this, dataObject, DragDropEffects.Copy); } } e.Handled = true; } } private childItem FindVisualChild&lt;childItem&gt;(DependencyObject obj) where childItem : DependencyObject { for (int i = 0; i &lt; VisualTreeHelper.GetChildrenCount(obj); i++) { DependencyObject child = VisualTreeHelper.GetChild(obj, i); if (child != null &amp;&amp; child is childItem) return (childItem)child; else { childItem childOfChild = FindVisualChild&lt;childItem&gt;(child); if (childOfChild != null) return childOfChild; } } return null; } } </code></pre> <p>here is the xaml file for ToolBox and toolbox item:</p> <pre><code> &lt;Style TargetType="{x:Type s:ToolboxItem}"&gt; &lt;Setter Property="Control.Padding" Value="5" /&gt; &lt;Setter Property="ContentControl.HorizontalContentAlignment" Value="Stretch" /&gt; &lt;Setter Property="ContentControl.VerticalContentAlignment" Value="Stretch" /&gt; &lt;Setter Property="ToolTip" Value="{Binding ToolTip}" /&gt; &lt;Setter Property="Template"&gt; &lt;Setter.Value&gt; &lt;ControlTemplate TargetType="{x:Type s:ToolboxItem}"&gt; &lt;Grid&gt; &lt;Rectangle Name="Border" StrokeThickness="1" StrokeDashArray="2" Fill="Transparent" SnapsToDevicePixels="true" /&gt; &lt;ContentPresenter Content="{TemplateBinding ContentControl.Content}" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding UIElement.SnapsToDevicePixels}" ContentTemplate="{TemplateBinding ContentTemplate}"/&gt; &lt;/Grid&gt; &lt;ControlTemplate.Triggers&gt; &lt;Trigger Property="IsMouseOver" Value="true"&gt; &lt;Setter TargetName="Border" Property="Stroke" Value="Gray" /&gt; &lt;/Trigger&gt; &lt;/ControlTemplate.Triggers&gt; &lt;/ControlTemplate&gt; &lt;/Setter.Value&gt; &lt;/Setter&gt; &lt;/Style&gt; &lt;Style TargetType="{x:Type s:Toolbox}"&gt; &lt;Setter Property="SnapsToDevicePixels" Value="true" /&gt; &lt;Setter Property="Focusable" Value="False" /&gt; &lt;Setter Property="Template"&gt; &lt;Setter.Value&gt; &lt;ControlTemplate&gt; &lt;Border BorderThickness="{TemplateBinding Border.BorderThickness}" Padding="{TemplateBinding Control.Padding}" BorderBrush="{TemplateBinding Border.BorderBrush}" Background="{TemplateBinding Panel.Background}" SnapsToDevicePixels="True"&gt; &lt;ScrollViewer VerticalScrollBarVisibility="Auto"&gt; &lt;ItemsPresenter SnapsToDevicePixels="{TemplateBinding UIElement.SnapsToDevicePixels}" /&gt; &lt;/ScrollViewer&gt; &lt;/Border&gt; &lt;/ControlTemplate&gt; &lt;/Setter.Value&gt; &lt;/Setter&gt; &lt;Setter Property="ItemsPanel"&gt; &lt;Setter.Value&gt; &lt;ItemsPanelTemplate&gt; &lt;WrapPanel Margin="0,5,0,5" ItemHeight="{Binding Path=DefaultItemSize.Height, RelativeSource={RelativeSource AncestorType=s:Toolbox}}" ItemWidth="{Binding Path=DefaultItemSize.Width, RelativeSource={RelativeSource AncestorType=s:Toolbox}}" /&gt; &lt;/ItemsPanelTemplate&gt; &lt;/Setter.Value&gt; &lt;/Setter&gt; &lt;/Style&gt; &lt;/ResourceDictionary&gt; </code></pre> <p>Example usage:</p> <pre><code>&lt;Toolbox x:Name="NewLibrary" DefaultItemSize="55,55" ItemsSource="{Binding}" &gt; &lt;ItemsControl.ItemTemplate&gt; &lt;DataTemplate&gt; &lt;StackPanel&gt; &lt;Image Source="{Binding Path=url}" /&gt; &lt;/StackPanel&gt; &lt;/DataTemplate&gt; &lt;/ItemsControl.ItemTemplate&gt; &lt;/Toolbox&gt; </code></pre> <p>The object that I get is a database object. When using a static resource I get the Image object. How to retrieve this Image object from a datatemplate? I though that I could use this tutorial: <a href="http://msdn.microsoft.com/en-us/library/bb613579.aspx" rel="nofollow noreferrer">http://msdn.microsoft.com/en-us/library/bb613579.aspx</a> But it does not seem to solve the problem. Could anyone suggest a solution? Thanks!</p>
 

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