Resolving the Issue of Ajax Function Always Returning undefined in ASP.NET Core

Discover why your AJAX call is returning undefined and learn how to fix it effectively in ASP.NET Core applications.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Ajax Function Always Returning undefined

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding the Ajax Function Returning undefined

When you're developing applications using ASP.NET Core and AJAX, a common problem that many developers encounter is receiving an undefined response. This can lead to confusion, especially when you expect to retrieve meaningful data from your server. In this post, we'll break down the issue of the AJAX function returning undefined and provide a clear solution to resolve it.

The Problem at Hand

Your code set-up appears relatively straightforward. You're sending a JavaScript object to your server and expecting it to return some data. However, instead of the data you expect, you find yourself staring at an undefined response. Here’s a summary of your code setup:

JavaScript: Using jQuery to send an AJAX POST request.

C# Controller: Handling the incoming request in your ASP.NET Core application.

The AJAX request looks something like this:

[[See Video to Reveal this Text or Code Snippet]]

And your C# controller action looks like this:

[[See Video to Reveal this Text or Code Snippet]]

The AJAX call is expecting a response that includes Name and DateTime. The problem arises because the C# method returns a view instead of JSON data.

The Solution Explained

Returning JSON Data

To fix the issue, you need to return a JSON object instead. This is how you can modify the controller action:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes

Here’s a breakdown of the changes made:

Return Type: Rather than return View();, we use return Json(...) to ensure that we are sending back JSON data rather than HTML content.

JSON Object: The object returned now contains properties Name and DateTime, which match the expectation from the AJAX success callback.

Conclusion

By making these adjustments, your AJAX function will respond with the expected JSON data, allowing you to successfully access the properties response.Name and response.DateTime. No longer will you encounter the frustrating undefined value!

This solution highlights the importance of matching the data type expected by the client-side code with the response sent from the server. With this in mind, you can troubleshoot similar issues in your future development work.

Remember, when dealing with AJAX requests, always ensure that the server responds with the correct data type that your client-side code is designed to handle!