I was writing some Unit Tests on default ASP.NET MVC Movie Application. Application can be created by following tutorials here http://www.asp.net/mvc/tutorials/mvc-5/introduction/getting-started or alternatively you can download sample application as well. Okay so while writing unit test, I had to pass null value for id in Edit action. Compiler was not happy me passing null and I got compile time error as given in below image,

Error is clearly saying that there is ambiguous between two methods. On examining Edit action found it was overloaded,

• Id parameter
• Instance of Movie parameter

Now when I passed null, complier was not able to decide which overloaded Edit action needed to be called. Because null can be pass for integer id value and for object Movie as well. And that’s the reason complier was throwing compile time error.

How to solve it? Of course you can change definition of Edit action. But we may not want to do it. Other option is to forcefully pass null either as movie or integer id. Null can be passed as integer id as below,

Remember this solution not restricted only for MVC and can work in any code written using C#. So, the call is ambiguous between the following methods in C# can be resolved as easily as given discussed above.