PostAsJsonAsync doesnt seem to post body parameters

Question

I have created an Azure logic app that exposes a REST endpoint.

The following JSON body works fine when I call it through postman.

{
   "to": "[email protected]",
   "subject": "Hello there",
   "message": "Hello there!!!!!"
}

I'm able to see the incoming request formed nicely

{
    "headers": {
        "Cache-Control": "no-cache",
        "Connection": "keep-alive",
        "Accept": "*/*",
        "Accept-Encoding": "gzip,deflate",
        "Host": "maskedout.northcentralus.logic.azure.com:443",
        "User-Agent": "PostmanRuntime/6.4.1",
        "Content-Length": "99",
        "Content-Type": "application/json"
    },
    "body": {
        "to": "[email protected]",
        "subject": "Hello there",
        "message": "Hello there!!!!!"
    }
}

However, when I try to make the same call using C# PostAsJsonAsync with this code:

        var email = new Email
        {
            to = "[email protected]",
            subject = "from webapp",
            message = "hello world"
        };
        var client = new HttpClient();
        var uri = "maskedout";
        var response = await client.PostAsJsonAsync<Email>(uri, email);

I'm able to call my REST endpoint successfully, but it does not contain the body

This is the incoming request I see:

{
    "headers": {
        "Connection": "Keep-Alive",
        "Transfer-Encoding": "chunked",
        "Host": "maskedout.northcentralus.logic.azure.com",
        "x-ms-request-root-id": "9e5513c2-43961642a3688718",
        "x-ms-request-id": "|9e5513c2-43961642a3688718.1.",
        "Request-Id": "|9e5513c2-43961642a3688718.1.1.",
        "Content-Type": "application/json; charset=utf-8",
        "Content-Length": "0"
    }
}

What am I missing here? What's different in my C# code compared to postman?

Answer 1

I've just run into this problem too. The issue appears to be the Content-Length header. In Postman it is the length of the content but using HttpClient the length is 0 so I am guessing the endpoint is ignoring the body as it is being told it is empty.

I created my own extension to get around this:

public static async Task<HttpResponseMessage> PostJsonAsync<T>(
        this HttpClient client,
        string requestUri,
        T value)
    {
        var data = JsonConvert.SerializeObject(value);
        var content = new StringContent(data,
                                        Encoding.UTF8,
                                        MimeTypes.Json);
        Debug.WriteLine(client.BaseAddress + requestUri);
        return await client.PostAsync(requestUri,
                                      content)
                           .WithRequestTimeout()
                           .ConfigureAwait(false);
    }