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POWPF custom control XAML null error
 

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    <p>Yet another strange WPF error:</p> <p>I have a custom control in a simple XAML page. The project builds and runs perfectly, with no errors. </p> <p>Here's the XAML:</p> <pre><code>&lt;Window x:Class="Grapher2.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:graph="clr-namespace:Grapher2" Title="Grapher" Width="800" Height="600"&gt; &lt;StackPanel Name="container" Width="700" Height="500"&gt; &lt;graph:GraphCanvas x:Name="graphCanvas" Width="700" Height="500" Background="#ddd" /&gt; &lt;/StackPanel&gt; </code></pre> <p></p> <p>But when I try to view the XAML page in the XAML designer window, I get the message:</p> <blockquote> <p>"Problem Loading--The document contains errors that must be fixed..." </p> </blockquote> <p>When I hit the "Reload the designer" link, an error pops up in the Error List which says:</p> <blockquote> <p>"Object reference not set to an instance of an object" </p> </blockquote> <p>and the line starting with "graph:GraphCanvas..." is underlined.</p> <p>I was originally developing on our development server, and there, everything was the same, except the error was:</p> <blockquote> <p>"Request for the permission of type 'System.Security.Permissions.SecurityPermission (...blah blah... failed.)"</p> </blockquote> <p>Again, everything works perfectly, except that I can't view the page in the XAML designer window, which is keeping me from developing the rest of the app.</p> <p>I've tried cleaning, building, rebuilding, and all combinations of orders of these commands, with no success.</p> <p><strong>EDIT:</strong></p> <p>Please bear in mind this is my first custom control, and I could be doing something horribly, horribly wrong. Like I said, the app compiles and works beautifully, so I'm kinda mystified.</p> <p><strong>EDIT #2:</strong></p> <p>My derived canvas is not a partial class. From my understanding of how <code>InitializeComponent</code> works (<a href="https://stackoverflow.com/questions/245825/what-does-initializecomponent-do-and-how-does-it-work-wpf">What does InitializeComponent() do, and how does it work in WPF?</a>), there is no auto-generated partial class that contains <code>InitializeComponent</code> linked to my control. Again, the control works perfectly without it, except for breaking the XAML design view.</p>
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