Question

I’m trying to create a custom WPF control and place it inside of a StackPanel in my XAML file. I originally made a custom UserControl and got the following error message:

A value of type 'CustomControl' cannot be added to a collection or dictionary of type 'UIElementCollection'.

I tried changing my custom control from a UserControl to a UIElement, but I still get this message. How do I make a custom control that I can place inside of the StackPanel?

Answer 1

How are you creating the CustomControl? Make sure it is inheriting from UserControl.

I just created a new project called “TestProj” – right clicked in the solution explorer Add=>UserControl and named it CustomControl.

I was able to insert it via the following code:

<Window x:Class="TestProj.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:TestProj"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <StackPanel>
        <local:CustomControl/>
    </StackPanel>
</Grid>