WPF: VS2012 designer shows "The component 'XXX' does not have a resource identified by the URI YYY"

Question

As the title suggests, this error is thrown by the designer, which means the designer can't display my UserControl correctly which in turn means I can't navigate smoothly from element to element in this UserControl to make modification. Really annoying.

XXX is the name of my UserControl, while the URI YYY is actually XXX's path. So I don't know understand it can't find itself as resource. I googled this error, but most of them happened in the runtime. In my case it doesn't happen at all when I execute it. The description of this error is really not explanatory enough, because I am not sure who in the CLR is loading the file itself as a resource.

Another thing might be worth mentioning is, this error only happens after I build my application project, which the error UserControl resides in. After I click to clean the project, the designer can display the whole stuff (but obviously I can't clean the project every time before I make any change, since the building takes time)

Answer 1

It is possible that the control's .g.cs or .g.i.cs file has been corrupted. Try to clean, close visual studio and restart it. I think that helped for me in several cases especially when I copy paste controls from one solution to another.

Answer 2

Just delete subfolders in

%LOCALAPPDATA%\Microsoft\VisualStudio\12.0\Designer\ShadowCache

Answer 3

If you refactor a UserControl down a lower level project that the UserControl was previously referencing then you will see this error.

Removing the assembly reference from the namespace fixes the issue.

<UserControl xmlns:ui="clr-namespace:MyCompany.Core.UI;assembly=MyCompany.Core.UI"

should be

<UserControl xmlns:ui="clr-namespace:MyCompany.Core.UI"

The designer is not smart enough to highlight this.