Web Api参数始终为null

Question

Why is the parameter always null when I call the below Post method with the below ajax?

public IEnumerable<string> Post([FromBody]string value)
{
    return new string[] { "value1", "value2", value };
}

Here is the call to the Web API method via ajax:

  function SearchText() {
        $("#txtSearch").autocomplete({
            source: function (request, response) {
                $.ajax({
                    type: "POST",
                    contentType: "application/json; charset=utf-8",
                    url: "api/search/",
                    data: "test",
                    dataType: "text",
                    success: function (data) {
                        response(data.d);
                    },
                    error: function (result) {
                        alert("Error");
                    }
                });
            }
        });
    }

Answer 1

You cannot use a simple type for the [FromBody] attribute with the JSON content type. Although the default in Visual Studio has a string from body this is for the application/x-www-form-urlencoded content type.

Put the string value as a property on a basic model class and the deserialiser will work.

public class SimpleModel()
{
    public string Value {get;set;}
}

public IEnumerable<string> Post([FromBody]SimpleModel model)
{
    return new string[] { "value1", "value2", model.Value };
}

Change the JSON you are sending to:

{"Value":"test"}