Cannot add content to object of type 'Microsoft.Toolkit.Wpf.UI.XamlHost.WindowsXamlHost'

Question

Hi Q&A,

The error MC3028 'Cannot add content to object of type 'Microsoft.Toolkit.Wpf.UI.XamlHost.WindowsXamlHost'' appears when trying to add any control (in the conventional manner) to the StackPanel.

I am new to xaml islands; however, there must be some way to add controls, eg text boxes, otherwise what good is it?

What is singularly frustrating, is that all the documentation/samples I can find, either from microsoft or bloggers, only shows a WindowsXamlHost button added to a wpf page.

        <xamlhost:WindowsXamlHost x:Name="StackPanel" InitialTypeName="Windows.UI.Xaml.Controls.StackPanel"  >
*-> any control added here gives the error*
      </xamlhost:WindowsXamlHost>

Any pointers in the right direction would be much appreciated - I've been looking for hours.

Answer 1

Please refer to WindowsXamlHost control for Windows Forms and WPF to crate a demo to use windowsxamlhost. After
After successfully adding an demo of Button, please replace the Button by StackPanel as below:

        <xamlhost:WindowsXamlHost x:Name="myStackPanel" InitialTypeName="Windows.UI.Xaml.Controls.StackPanel" Width="600" Height="300" Loaded="myStackPanel_Loaded" />  
  

Its cs code is:

private void myStackPanel_Loaded(object sender, RoutedEventArgs e)  
        {  
            WindowsXamlHost windowsXamlHost = (WindowsXamlHost)sender;  
  
            Windows.UI.Xaml.Controls.StackPanel myStackPanel =  
                (Windows.UI.Xaml.Controls.StackPanel)windowsXamlHost.Child;  
  
            myStackPanel.Width = 400;  
            myStackPanel.Height = 200;  
  
            Windows.UI.Xaml.Controls.Button myButton = new Windows.UI.Xaml.Controls.Button() { Content = "Button1", Height = 40, Width = 100 };  
            Windows.UI.Xaml.Controls.TextBlock myTextBlock = new Windows.UI.Xaml.Controls.TextBlock() { Text = "This is TextBlock", Height = 40, Width = 100 };  
            myButton.Click += MyButton_Click;  
  
            myStackPanel.Children.Add(myButton);  
            myStackPanel.Children.Add(myTextBlock);  
        }  
        private void MyButton_Click(object sender, Windows.UI.Xaml.RoutedEventArgs e)  
        {  
            MessageBox.Show("This is Windows.UI.Xaml.Controls.Button");  
        }  

The result picture is:

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Answer 2

Thank you for the reply; however, are you saying there is no way to do this in xaml?
I am trying to follow the mvvm pattern, and am using the Microsoft.Toolkit.Mvvm, also from the Community toolkit. As I understand, code behind in the View is not part of the pattern. And since I wanted to use the stack panel in an ItemTemplate with multiple text boxes etc, the code behind solution is not really an option.

There seems to be a xaml child element tag, which the editor accepts. This gives two errors:
XDG0038 The property "Child" cannot be empty.
MC3063 Property 'Child' does not have a value.

 <xamlhost:WindowsXamlHost x:Name="StackPanel" InitialTypeName="Windows.UI.Xaml.Controls.StackPanel"  >
 <xamlhost:WindowsXamlHost.Child>


 </xamlhost:WindowsXamlHost.Child>
 </xamlhost:WindowsXamlHost>

Also tried:

        <xamlhost:WindowsXamlHost x:Name="StackPanel" InitialTypeName="Windows.UI.Xaml.Controls.StackPanel"  >
            <xamlhost:WindowsXamlHost.Child  x:Name="txtBox" InitialTypeName="Windows.UI.Xaml.Controls.TextBox">

            </xamlhost:WindowsXamlHost.Child>
        </xamlhost:WindowsXamlHost>

And also got two errors:
MC3057 Cannot set properties on property elements.
XDG0038 The property "Child" cannot be empty.

If this is not possible, then returning to the old wpf stack panel is not such a problem.