Azure Functions - Difference between return type HttpResponseMessage and IActionResult

Question

I have created Http Trigger Azure Function and its default return type is Task<IActionResult>.

Is there any difference if I changed it to Task<HttpResponseMessage>?

Azure function with Task<IActionResult> return type:

 public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Function, "post", Route = null)] HttpRequest req,

Azure function with Task<HttpResponseMessage>

 public static async Task<HttpResponseMessage> Run(
            [HttpTrigger(AuthorizationLevel.Function, "post", Route = null)]
            HttpRequestMessage message,

Answer 1

Is there any difference if I changed Task<IActionResult> to Task<HttpResponseMessage>?

You can use the Task<HttpResponseMessage> to be the return type of your function. There shouldn't be a problem in executing with that.

Having said that, the difference between using the two lies in just the way you return response from your function.

• In case of an IActionResult type of response, there is lesser code to write while constructing a response and it makes unit testing simpler.
• On the other hand, HttpResponseMessage gives more control on the Http response message sent across the wire.

Just as a side note,

In HttpTrigger Azure function v1.0, types Task<HttpResponseMessage> and HttpRequestMessage were used as defaults for return type and request type respectively.

From v2.0 onwards, types Task<IActionResult> and HttpRequest are being used as default return type and request type respectively as it conforms to .net core API structure.