The call is ambiguous between single method i.e extension method

Question

I have an extension method like

public static class Extension {     public static string GetTLD(this string str)     {         var host = new System.Uri(str).Host;         int index = host.LastIndexOf('.'), last = 3;         while (index >= last - 3)         {             last = index;             index = host.LastIndexOf('.', last - 1);         }         var domain = host.Substring(index + 1);         return domain;     } } 

And I am calling this like

string domain = "." + _url.GetTLD(); 

I am getting no error at building and clean build.
But I am getting compilation error at run time error saying

The call is ambiguous between the following methods or properties: 'myIGNOU.Extension.GetTLD(string)' and 'myIGNOU.Extension.GetTLD(string)'

I swear that I don't have this extension method placed any where else too in the project. Why I am getting this error only at run time..?

But if I delete this method then I am getting error at build time not not at run time. Everything works fine without the code of this method.

Here is compilation error page

Answer 1

I had the same problem but for me it solved the problem to remove the own project from the project references. Resharper accidentally added a reference to the compiled binary of the same project. That way I had the same extension class 2 times within my project. During building it couldn't distinguish between the source-version or the binary-version of the extension class.

So basically: Check your project references if it contains a reference to itself.

Answer provided by @shashwat is also a case.

Answer 2

This is not a real solution and I can't explain how did it work but it worked.

I was trying everything in Project Properties, References, bin, obj but nothing helped me really. And I was just trying every option and chose 'Convert to Web Application' from the context menu. Although It was a Web Application itself before. It showed me a warning saying that .designer.cs files will be added to each aspx file and I just clicked OK.

Everything remained same except App_Code folder (where all these classes were) was renamed to Old App_Code and I'd build the project. And now I am not getting compilation error at run time.

I know App_Code folder are meant to Website Project and I was having no issue with this till this time in WAP. But I just realize I should not have App_Code folder in WAP as it is discussed here in a wrox forum (1st point). Author has said here that

App_Code is not supported in a WAP. The App_Code folder is compiled at run-time; all code in a WAP is compiled at compile / development time. So, when you add an App_Code folder to a WAP. you end up with duplicate code; for example, a class defined in App_Code will also show up in the wap DLL. The fix is easy: just name the folder something else like Classes or CodeFiles.

I have tried it renaming too before conversion but that time it did not work.