first= 111 &second= 222 

  [WebService( Namespace = "http://tempuri.org/" )]
  [WebServiceBinding( ConformsTo = WsiProfiles.BasicProfile1_1 )]
  [System.ComponentModel.ToolboxItem( false )]
  [System.Web.Script.Services.ScriptService]
  public class ListingService : WebService
  {
    [WebMethod]
    public string SampleMethod( string first, string second )
    {
      return string.Format( "Hello, {0} {1}!", first, second );
    }
  }

function callService()
{
  var data = { first: "Ivan", second: "Petrov" };
  $.ajaxDotNet( g_ListingServicePath + "/SampleMethod",
                { verb: "POST",
                  data: data,
                  success: function( obj ) 
                  {
                    alert( "Call succeeded: «" + obj.d + "»" );
                  }
                } 
              );

}

POST /Services/ListingService.asmx/SampleMethod HTTP/ 1 . 1 
Host: localhost
User-Agent: Mozilla/ 5 . 0  (Windows; U; Windows NT  5 . 2 ; en-US; rv: 1 . 9 . 0 . 10 ) Gecko/ 2009042316  AdCentriaIM/ 1 . 7  Firefox/ 3 . 0 . 10  (.NET CLR  3 . 5 . 30729 )
Accept: text/html,application/xhtml+xml,application/xml;q= 0 . 9 ,*/*;q= 0 . 8 
Accept-Language: en-us,en;q= 0 . 5 
Accept-Encoding: gzip,deflate
Accept-Charset: ISO- 8859 - 1 ,utf- 8 ;q= 0 . 7 ,*;q= 0 . 7 
Keep-Alive:  300 
Connection: keep-alive
Content-Type: application/json; charset=utf- 8 
Content-Length:  34 
Pragma: no-cache
Cache-Control: no-cache

{"first":"Ivan","second":"Petrov"}

first=Ivan&second=Petrov