What is wrong with this ASP.Net and Fiddler example? - asp.net-web-api

Question

I am using Visual Studio 2012 RC. I am using the default routes and have the following Web API controller:
public class FooController : ApiController
{
// GET api/foo
public IEnumerable<string> Get()
{
return new string[] { "value1", "value2" };
}
// GET api/foo/5
public string Get(int id)
{
return "value";
}
// POST api/foo
public string Post(string abc)
{
Console.WriteLine("value: {0}", abc);
return "foo" + abc;
}
// PUT api/foo/5
public void Put(int id, string value)
{
}
// DELETE api/foo/5
public void Delete(int id)
{
}
}
I wanted to do a simple test of POST in Fiddler, so I have
Request Headers
User-Agent: Fiddler
Content-Type: application/json
Request Body
{"abc": "def"}
When I debug the request, the parameter abc comes in as null, not "def". Is there something wrong with my Fiddler syntax?

Answer 1

(1) By default, simple types are taken from the URI. To read a simple type from the request body, add the [FromBody] attribute to the parameter.
public string Post([FromBody] string abc)
(2) '{"abc": "def"}' defines an object with a property named "abc" - to send a JSON string, the request body should just be "def"

Answer 2

This answer comes from a link on the ASP.Net Web API site sending-html-form-data , which turns out to be Mike's blog post (I didn't realize that at first). The Web API team has made a few decisions with parameter binding that are quite different from normal MVC controllers.
The correct syntax for sending "simple types" is
public HttpResponseMessage PostSimple([FromBody] string value)
{
// code goes here
And in Fiddler, you put
=def //THIS CANNOT HAVE QUOTES AND = IS MANDATORY
OK, so here are the parts that work very differently from MVC.
You must use [FromBody], as Mike says.
You can only have 1 parameter. If you want more than 1 parameter, you have 2 choices: i) use url query parameters, instead of request body or ii) use a complex object (i.e. your own class).
The request body should be a simple =def and cannot use named parameters.