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POWPF: Error using a custom control in the ItemTemplate of another custom control
 

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  1. POWPF: Error using a custom control in the ItemTemplate of another custom control
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    <p>I have a custom control library where I have several custom controls that I use in my main application. I have a simple custom control that lets the user select pen thickness values from a combobox. Now, I am creating a new custom control, based on a listbox, and I want to include the pen thickness combobox in the new custom control's ItemTemplate.</p> <p>I am getting this error:</p> <p><strong>"Cannot create instance of "LineThicknessComboBox" defined in assembly CustomControls ... Exception has been thrown by the target of an invocation. Error at object "10_T" in markup file 'CustomControls;component/Themes/CustomListBox.General.xaml'.</strong></p> <p>Here is the XAML and code behind for the LineThicknessComboBox:</p> <pre><code>namespace CustomControls { public class LineThicknessComboBox : ComboBox { public LineThicknessComboBox() { DefaultStyleKeyProperty.OverrideMetadata(typeof(LineThicknessComboBox) , new FrameworkPropertyMetadata(typeof(LineThicknessComboBox))); } } } </code></pre> <p>and in LineThicknessCombobox.Generic.xaml:</p> <pre><code>&lt;ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:CustomControls"&gt; &lt;Style TargetType="{x:Type local:LineThicknessComboBox}" BasedOn="{StaticResource {x:Type ComboBox}}"&gt; &lt;Setter Property="ItemTemplate"&gt; &lt;Setter.Value&gt; &lt;DataTemplate&gt; ... &lt;/DataTemplate&gt; &lt;/Setter.Value&gt; &lt;/Setter&gt; &lt;/Style&gt; &lt;/ResourceDictionary&gt; </code></pre> <p>Here is the XAML and codebehind for my new CustomListBox:</p> <pre><code>namespace CustomControls { public class CustomListBox : ListBox { public CustomListBox() { DefaultStyleKeyProperty.OverrideMetadata(typeof(CustomListBox) , new FrameworkPropertyMetadata(typeof(CustomListBox))); } } } </code></pre> <p>and in CustomListBox.Generic.xaml:</p> <pre><code>&lt;ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:CustomControls"&gt; &lt;Style TargetType="{x:Type local:CustomListBox}" BasedOn="{StaticResource {x:Type ListBox}}"&gt; &lt;Setter Property="ItemTemplate"&gt; &lt;Setter.Value&gt; &lt;DataTemplate&gt; &lt;Border&gt; ... &lt;local:LineThicknessComboBox /&gt; ... &lt;/Border&gt; &lt;/DataTemplate&gt; &lt;/Setter.Value&gt; &lt;/Setter&gt; &lt;/Style&gt; &lt;/ResourceDictionary&gt; </code></pre> <p>And here is my Generix.xaml:</p> <pre><code>&lt;ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt; &lt;ResourceDictionary.MergedDictionaries&gt; &lt;ResourceDictionary Source="CustomControls;component/Themes/LineThicknessComboBox.Generic.xaml"/&gt; &lt;ResourceDictionary Source="CustomControls;component/Themes/CustomListBox.Generic.xaml"/&gt; &lt;/ResourceDictionary.MergedDictionaries&gt; &lt;/ResourceDictionary&gt; </code></pre> <p>I'm thinking I have some kind of reference problem, but can't figure out what is wrong. The program compiles and runs without any warnings/errors but when the CustomListBox is created in my main application, I get the error listed above. Without including the LineThicknessComboBox, the CustomListBox works fine.</p> <p>Can anyone explain why I am getting this error? It is possible to include my custom control in another, even though they are in the same custom control library, correct?</p> <p>Thanks!</p>
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    1. USstevosaurus
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    1. CO"Exception has been thrown by the target of an invocation." Drill into the InnerException (you may need to drill down more than one level) and you should find a more meaningful exception. That may make the error obvious once you see it, or failing that if you could post it, it would help with the diagnosis.
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      1. POWPF: Error using a custom control in the ItemTemplate of another custom control
      1. USitowlson
 

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