How to return raw string with ApiController?

I have an ApiController that serves XML/JSON, but I would like one of my actions to return pure HTML. I tried the below but it still return XML/JSON.

public string Get()
{
    return "<strong>test</strong>";
}

This is what the above returns:

<string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">&lt;strong&gt;test&lt;/strong&gt;</string>

Is there a way to return just the pure, unescaped text without even the surrounding XML tags (maybe a different return type of action attribute)?

You could have your Web Api action return an HttpResponseMessage for which you have full control over the Content. In your case you might use a StringContent and specify the correct content type:

public HttpResponseMessage Get()
{
    return new HttpResponseMessage()
    {
        Content = new StringContent(
            "<strong>test</strong>", 
            Encoding.UTF8, 
            "text/html"
        )
    };
}

or

public IHttpActionResult Get()
{
    return base.ResponseMessage(new HttpResponseMessage()
    {
        Content = new StringContent(
            "<strong>test</strong>", 
            Encoding.UTF8, 
            "text/html"
        )
    });
}

Another possible solution. In Web API 2 I used the base.Content() method of APIController:

    public IHttpActionResult Post()
    {
        return base.Content(HttpStatusCode.OK, new {} , new JsonMediaTypeFormatter(), "text/plain");
    }

I needed to do this to get around an IE9 bug where it kept trying to download JSON content. This should also work for XML-type data by using the XmlMediaTypeFormatter media formatter.

Hope that helps someone.