Why FromBody Behave like this ? - asp.net-web-api

Question

I want to understand why FromBody behave like this for common request.
Case 1:
Controller
public void Post([FromBody]string value)
{
}
POSTMAN Request
Problem
In this case value is my post method will not bind to value parameter to test.
Case 2:
Model
public class Test
{
public string value { get; set; }
}
Controller
public void Post([FromBody]Test model)
{
}
POSTMAN Request
Same as Case 1
Result :
Now model value property successfully bind to "test".
Why it is behave like this ?

Answer 1

Because that's the way the API was designed. Note that in your second example you could have elided [FromBody] and WebApi would have searched the body for the data anyways because Test is a complex type.
This article explains the rules by which WebApi binds data:
http://blogs.msdn.com/b/jmstall/archive/2012/04/16/how-webapi-does-parameter-binding.aspx
EDIT: As commented, the article linked above clearly states you should be able to do
void Get([FromBody]string value)
This is true, but it means you can read the value of the body as plain text into the parameter value. This means if you go this route, you MUST use the raw option (from postman) and either clear Content-Type or make sure it's set to text/plain.
In other words, on Postman, if you set the send method to raw, and type in "this is a sentence" as is in the text area provided, your value, when the issue below is fixed, will be "this is a sentence".
Now, if you tried doing this from a fresh template, you will run into this error:
{
"Message": "The request entity's media type 'text/plain' is not supported for this resource.",
"ExceptionMessage": "No MediaTypeFormatter is available to read an object of type 'String' from content with media type 'text/plain'.",
"ExceptionType": "System.Net.Http.UnsupportedMediaTypeException",
"StackTrace": " at System.Net.Http.HttpContentExtensions.ReadAsAsync[T](HttpContent content, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger, CancellationToken cancellationToken)\r\n at System.Net.Http.HttpContentExtensions.ReadAsAsync(HttpContent content, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger, CancellationToken cancellationToken)\r\n at System.Web.Http.ModelBinding.FormatterParameterBinding.ReadContentAsync(HttpRequestMessage request, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger, CancellationToken cancellationToken)"
}
This article explains how to allow WebApi to accept text/plain data from the body:
https://myadventuresincoding.wordpress.com/2012/06/19/c-supporting-textplain-in-an-mvc-4-rc-web-api-application/
It's kind of stupid that the default ValuesController exposes a method with that signature, but does not provide a MediaTypeFormatter for text/plain, but I guess that's Microsoft for you.

Answer 2

Given this method:
// POST api/values
[HttpPost]
public void Post([FromBody]string value)
{
Values.Add(value);
}
Postman must be configured correctly in order for our value to bind to its C# string object...one way to ensure this works in our case is to send our server a JSON request. Follow these steps:
Make sure you've selected POST.
Make sure you've entered an appropriate URL, i.e. http://localhost:1337/api/values.
Go to Body, tick the option for raw.
In the drop-down to the right, select JSON (application/json).
In the text area of Postman, insert only "Hello, world." (with the quotes as well, otherwise it won't be valid JSON).
It should now work once you hit Send.

Answer 3

For JSON you can do this:
public HttpResponseMessage Webhook(JToken json)
{
}
Where JToken is Newtonsoft.Json.Linq.JToken.
JObject works if the data is an actual JSON object (not an array)