I'm using Web API 2 and I'm getting the following error when I send a POST to my API method using IIS 7.5 on my local box.

The inline constraint resolver of type 'DefaultInlineConstraintResolver' was unable to resolve the following inline constraint: 'string'.

Line 21: GlobalConfiguration.Configuration.EnsureInitialized();

None of my APIs work using IIS. However, I'm able to run my API project in Visual Studio using IIS Express and successfully make a POST to my login API, but when I try and make a GET request to another API call, I get the constraint resolver error.

In order to troubleshoot this, I created a brand new Web API 2 project in Visual Studio and started importing the existing APIs into the new project one at a time and running them to ensure they work. Using IIS Express with this new project, I get the same exact results as I did with my existing API project.

What am I missing here? Even with a brand new project I'm not able to make GET requests without running into this constraint resolver issue.