kendo ui web selected combobox value set in textbox

Here i am using razor view

 <div class="editor-label">  
       @Html.LabelFor(model => model.ob_guid,"Im Objekt")  
     </div>  
     <div class="editor-field">  
       @(Html.Kendo().ComboBoxFor(model=>model.ob_guid)  
        .Name("categories")  
        .HtmlAttributes(new { style = "width:300px",id="categories" })  
        .Placeholder("Select category...")  
        .DataTextField("CategoryName")  
        .DataValueField("CategoryId")  
        .Filter(FilterType.Contains)  
        .DataSource(source =>  
        {  
          source.Read(read =>  
          {  
            read . Action ( "GetCascadeCategories" , "Limitations" );  
          });  
        })  
     )  
       </div>  
      <div class="editor-label">  
       @Html.LabelFor(model => model.von,"Code")  
     </div>  
     <div class="editor-field">  
       <input type="text" name="target" id="target" />  
     </div>  
     

<script>  
    $(document).ready(function () {  
      $("#categories").change(function () {  
        var url = '@Url.Content("~/")' + "Limitations/ThanaByDistrict_SelectedState";  
        var ddlsource = "#categories";  
        var ddltarget = "#target";  
        $.getJSON(url, { Sel_StateName: $(ddlsource).val() }, function (data) {  
          $(ddltarget).empty();  
          $(ddltarget).val(data);  
        });  
      });  
    });  
    </script>  

In my controller

  // Get object Combox vale  
     public JsonResult GetCascadeCategories ( )  
     {  
       return Json ( db . objects . Select ( c => new { CategoryId = c . ob_guid , CategoryName = c . ob_name } ) , JsonRequestBehavior . AllowGet );  
     }  
            // Get selected combox value  
     public JsonResult ThanaByDistrict_SelectedState ( Guid Sel_StateName )  
     {  
       JsonResult result = new JsonResult ( );  
       objects temp=db . objects . Single ( m => m . ob_guid == Sel_StateName );  
       result . Data = temp.ob_code;  
       result . JsonRequestBehavior = JsonRequestBehavior . AllowGet;  
       return result;  
     }