The call is ambiguous between the following methods: Identical.NameSpace.InitializeComponent() and Identical.NameSpace.InitializeComponent()

It appears that you have declared the InitializeComponent method in two places in your class, probably one in each partial class. Try searching in all files for InitializeComponent in Visual Studio and I'm guessing that the results will list two places where it is declared. Delete one and the error will disappear.

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UPDATE >>>

I'm not sure what kind of answer you're expecting here... clearly, if you didn't add one of those InitializeComponent method definitions, then visual Studio has a bug. I very much doubt that there can be any kind of logical reason for this except that it's a bug.

UPDATE 2 >>>

I had a look on the Microsoft Connect website for any existing reported bugs like this but couldn't find any... I've left the link here if you do want to report it to them.

I had this issue when copying my XAML between controls. I just had to change my x:Class="mynamespace" where mynamespace is the proper namespace for your project. Recompiled and all went back to normal.

My problem was the project that was giving me the ambiguous call had a reference to its own dll. This was causing the method to be referenced from the dll as well as in the actual project. Once i removed the dll from the references the ambiguous call error went away.