Put content in HttpResponseMessage object?

Several months ago, Microsoft decided to change up the HttpResponseMessage class. Before, you could simply pass a data type into the constructor, and then return the message with that data, but not anymore.

Now, you need to use the Content property to set the content of the message. The problem is that it is of type HttpContent, and I can't seem to find a way to convert a string, for example, to HttpContent.

Does anyone know how to deal with this issue? Thanks a lot.

For a string specifically, the quickest way is to use the StringContent constructor

response.Content = new StringContent("Your response text");

There are a number of additional HttpContent class descendants for other common scenarios.

You should create the response using Request.CreateResponse:

HttpResponseMessage response =  Request.CreateResponse(HttpStatusCode.BadRequest, "Error message");

You can pass objects not just strings to CreateResponse and it will serialize them based on the request's Accept header. This saves you from manually choosing a formatter.

Apparently the new way to do it is detailed here:

http://aspnetwebstack.codeplex.com/discussions/350492

To quote Henrik,

HttpResponseMessage response = new HttpResponseMessage();

response.Content = new ObjectContent<T>(T, myFormatter, "application/some-format");

So basically, one has to create a ObjectContent type, which apparently can be returned as an HttpContent object.

The easiest single-line solution is to use

return new HttpResponseMessage( HttpStatusCode.OK ) {Content =  new StringContent( "Your message here" ) };

For serialized JSON content:

return new HttpResponseMessage( HttpStatusCode.OK ) {Content =  new StringContent( SerializedString, System.Text.Encoding.UTF8, "application/json" ) };

For any T object you can do:

return Request.CreateResponse<T>(HttpStatusCode.OK, Tobject);

You can create your own specialised content types. For example one for Json content and one for Xml content (then just assign them to the HttpResponseMessage.Content):

public class JsonContent : StringContent
{
	public JsonContent(string content)
		: this(content, Encoding.UTF8)
	{
	}

	public JsonContent(string content, Encoding encoding)
		: base(content, encoding, "application/json")
	{
	}
}

public class XmlContent : StringContent
{
	public XmlContent(string content) 
		: this(content, Encoding.UTF8)
	{
	}

	public XmlContent(string content, Encoding encoding)
		: base(content, encoding, "application/xml")
	{
	}
}

Inspired by Simon Mattes' answer, I needed to satisfy IHttpActionResult required return type of ResponseMessageResult. Also using nashawn's JsonContent, I ended up with...

        return new System.Web.Http.Results.ResponseMessageResult(
            new System.Net.Http.HttpResponseMessage(System.Net.HttpStatusCode.OK)
            {
                Content = new JsonContent(JsonConvert.SerializeObject(contact, Formatting.Indented))
            });

See nashawn's answer for JsonContent.

No doubt that you are correct Florin. I was working on this project, and found that this piece of code:

product = await response.Content.ReadAsAsync<Product>();

Could be replaced with:

response.Content = new StringContent(string product);