Set request Content-Type on WinRT HttpClient

Question

I'm developing a Windows 8.1 Store apps with C# and .NET Framework 4.5.1.

I'm trying to do a POST to a REST API but I get an Unsupported Media Type with this code:

public async Task<HttpResponseMessage> POST(string url, string jsonContent)
{
    Uri resourceUri;

    resourceUri = ValidateUri(url);

    HttpClient httpClient = new HttpClient();
    HttpResponseMessage response = new HttpResponseMessage();

    HttpRequestHeaderCollection headers = httpClient.DefaultRequestHeaders;

    // Try to add user agent to headers.
    if (headers.UserAgent.TryParseAdd(_userAgent))
        headers.UserAgent.ParseAdd(_userAgent);

    // Add Content-Type and Content-Length headers
    headers.Accept.Add(new HttpMediaTypeWithQualityHeaderValue("application/json"));

    response = await httpClient.PostAsync(resourceUri, new HttpStringContent(jsonContent));

    return response;
}

If I change this line:

response = await httpClient.PostAsync(resourceUri, new HttpStringContent(jsonContent));

With this one:

response = await httpClient.PostAsync(resourceUri, new HttpStringContent(string.Empty));

It works. I don't get 415 status code.

jsonContent value is:

{"UserName":"My Name","Provider":"Facebook","ExternalAccessToken":"Access token omitted"}

Answer 1

Because I haven't found any similar code on Internet, and I only have 4 views on this question; I will share the answer.

I have fixed this problem changing the post with this code:

response = await httpClient.PostAsync(resourceUri,
    new HttpStringContent(jsonContent, UnicodeEncoding.Utf8, "application/json"));

You can pass "Content-Type" on HttpStringContent constructor. More info here.