Setting design time DataContext on a Window is giving a compiler error?

Question

I have the following XAML below for the main window in my WPF application, I am trying to set the design time d:DataContext below, which I can successfully do f

Answer 1

Wow, what a pain! Let's hope MS puts in some VS design-time support for x:Bind.

We to be able to use the VS designer but also be able to switch easily to x:Bind instead of Binding. Here's what I did:

• In my View, I added a property to get my ViewModel. This makes sense because x:Bind paths are relative to the Page (i.e. the View object).

• In my Page XAML, I added the following to the at the top of the XAML:

  mc:Ignorable="d" 
  d:DataContext="{d:DesignInstance Type=local:MyView, IsDesignTimeCreatable=False}" 
  DataContext="{x:Bind}"
  

This way, the Page's actual data context is set to the Page itself due to the {x:Bind}. That's because x:Bind is relative to the Page and there is no path given.

At the same time, due to the d:DataContext line, the VS designer reflects on the MyView class (without creating an instance) for the purpose of the VS designer interaction. This lets VS design from MyView, where you can then scroll down to the ViewModel property, expand it and select the item that you want to bind to.

When you do all that, the VS designer will create a Binding statement whose path is relative to the View, i.e. it happens to be exactly the same as the path that x:Bind expects. So, if you want to switch to x:Bind later on, you can just search and replace all "{Binding" with "{x:Bind".

Why do we even need the d:DataContext line to tell VS what class to look at? Good question, since you would think that VS could figure out the very next line sets the DataContext to the Page, using DataContext={x:Bind}. Go ahead and try it, it does not work and neither does it work if you change x:Bind to Binding relative to self.

Hopefully this situation will get cleaned up by MS !!