API Debugging in .NET: 7 Common Problems and How to Fix Them You send a request to an API. The endpoint looks correct, the server is running, and the request payload appears valid. Yet the response is 400 Bad Request , authentication fails, or the application returns an error that provides almost no useful information. Sound familiar? API debugging is an essential part of modern backend and full-stack development. Even experienced developers can spend hours investigating problems that eventually turn out to be a missing JSON property, an incorrect content type, an expired JWT token, or a mismatch between a request payload and a C# model. The real challenge is not just finding the error. It is identifying which layer of the API request is failing and why . In this guide, we'll explore seven common API debugging problems, demonstrate how to troubleshoot them using C# and ASP.NET Core, and explain how to identify the root cause without making unnecessary code changes. We...
