415 Unsupported Media Type

I had been struggling with a odd error when performing a POST from a WebApi project.

The server was refusing the request because the request is in a format not supported by that method.

The code causing the error:

    var content = new StringContent(json);
    HttpResponseMessage response = await client.PostAsync("Preview", content);

1 2	var content = new StringContent(json); HttpResponseMessage response = await client.PostAsync("Preview", content);

Fortunately the StringContent has an overload that allows the formatting to be supplied

    var content = new StringContent(json, Encoding.UTF8, "application/json");
    HttpResponseMessage response = await client.PostAsync("Preview", content);

1 2	var content = new StringContent(json, Encoding.UTF8, "application/json"); HttpResponseMessage response = await client.PostAsync("Preview", content);

And that fixes this error