Xaml designer doesn't show content of a userco

问题:

We have a specialized TabItem defined in xaml:

<TabItem  x:Class="MyApp.MyViewTab" xmlns:my="clr-namespace:MyApp">
    <my:MyView />
</TabItem>

and code behind: public class MyViewTab : TabItem. And MyView is a UserControl:

MyView is correctly shown in the xaml designer and also at run time correctly displayed as the content of the TabItem.

Why does the xaml designer not display the content of MyView? It is a gray rectangle, top half light-gray, bottom half darker-gray.

回答1:

Try splitting the screen between the UI designer and the code and then clicking on the code line where you declared your MyView control. This should focus the designer on the contents of that TabItem:

<TabItem  x:Class="MyApp.MyViewTab" xmlns:my="clr-namespace:MyApp">
    <my:MyView />   <!--Click here-->
</TabItem>

If you click anywhere within the TabItem, it should do the same.