Why Does a 200 OK Ajax Response Sometimes Trigger an Error Event?

200 OK Response Triggers Error Event in Ajax: Root Cause and Solution

When an Ajax request returns a 200 OK response, jQuery's default behavior is to execute the success event. However, in some cases, an error event may be triggered instead. This discrepancy arises from a mismatch between the expected response and the actual response.

The Case of Invalid JSON Response

In the example provided, the jQuery code specifies a dataType of "json." This triggers jQuery to expect a valid JSON response from the server. However, the C# code returns HTML with a 200 OK status code.

Since the response does not conform to the expected JSON format, jQuery interprets it as an error and fires the error event. To resolve this, it is recommended to remove the dataType parameter from the jQuery code. This will instruct jQuery to treat the response as a raw data string.

Returning a JavaScript Response

Another solution is to modify the server-side code to return a valid JavaScript response. This can be achieved by setting the Content-Type header to "application/javascript" and then embedding the desired JavaScript code (e.g., "alert('Record Deleted');") as the response.

Returning a JSON Response

For greater flexibility, it is often preferable to return a JSON response and handle the parsing and display in the success callback. To do this, the server-side code should:

1. Set the Content-Type header to "application/json"
2. Return a JSON object containing the desired message (e.g., {"message": "Record deleted"})

In the jQuery code, the success callback can then be modified to parse the JSON response and display the message accordingly.

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