Asp.net web api exception only after deploying at IIS : A route named 'HelpPage_Default' is already in the route collection

Question

I just ran into the same issue. I think the error was caused because I had pushed another solution to my site previously and there were leftover files that were somehow getting in the way.

To fix this I checked the box that says "Remove additional files at destination" while publishing through Visual Studio to my Azure site. I would assume you could just manually delete any old files that were on the server before publishing as well. After this the site ran fine with no errors.

1. Right click your solution in Visual Studio -> click Clean Solution
2. Remove all files under your \Project\bin\ folders
3. Rebuild your solution in Visual Studio Cheers.

I renamed a Namespace by refactoring it and doing that missed this hardcoded string:

Project > Areas > HelpPage > AppStart:

public static class HelpPageConfig
    {
        [SuppressMessage("Microsoft.Globalization", "CA1303:Do not pass literals as localized parameters",
            MessageId = "<CORRECT NAMESPACE>.Areas.HelpPage.TextSample.#ctor(System.String)",

I have the same issue after renamed the project name. So,

1. Find & Replace the correct name across the entire solution.
2. Clean solution
3. Delete bin & obj folder of the project.
4. Rebuild solution

..yes, it works.

I had this same issue and tried multiple proposed solutions from different threads with similar issues and got nowhere.

I finally just checked out a clean copy of the solution from team explorer and that fixed it for me.