How to consume XML Web Services with Parameters

//to allow call from script
[System.Web.Script.Services.ScriptService]
public class DummyService : System.Web.Services.WebService
{
   [WebMethod]
    public string DummyMethod(string id)
    {
        try
        {
              //TO DO: method implementation will goes here
              return id      
        }
        catch
        {
            return null;
        }
    }

   [WebMethod]
    public DummyModel DummyModelMethod(string id, string name)
    {
        try
        {
              //TO DO: method implementation will goes here
              return new DummyModel{Id=int.parse(id), Name=name};
        }
        catch
        {
            return null;
        }
    }
}
public class DummyModel 
{
   public int Id{set;get;}
   public int Name{set;get;}
}

function jqAjaxPost(webmethod, paramArray, successFn, errorFn) {   
    //Create list of parameters in the form : {"paramName1":"paramValue1","paramName2":"paramValue2"}      
    var paramList = '';
    if (paramArray.length > 0) {
        for (var i = 0; i < paramArray.length; i += 2) {
            if (paramList.length > 0)
                paramList += ',';
            paramList += '"' + paramArray[i] + '":"' + paramArray[i + 1] + '"';
        }
    }
    paramList = '{' + paramList + '}';
    //Call the page method
    $.ajax({
        type: "POST",
        url: webmethod,
        contentType: "application/json; charset=utf-8",
        data: paramList,
        dataType: "json",
        success: successFn,
        error: errorFn
    });
}

<script type="text/javascript">
jqAjaxPost("DummyService.asmx/DummyMethod",
                  ["id", "1"],
                  function (msg) {
                      if (msg.d == null) {
                          alert("service error.");                         
                          return;
                      }
                      //alert("sucsess");
                      alert(msg.d);
                  },
                    function () {
                        alert('service method not found');                       
                    });
jqAjaxPost("DummyService.asmx/DummyModelMethod",
                  ["id", "1", "name", "hoho"],
                  function (msg) {
                      if (msg.d == null) {
                          alert("service error.");                         
                          return;
                      }
                      //alert("sucsess");
                      alert(msg.d.Id);
                      alert(msg.d.Name);
                  },
                    function () {
                        alert('service method not found');                       
                    });
</script>