Question

I have a multiview on my ASPX page whose ActiveViewIndex I want to set using JavaScript. For this, I have used UpdatePanel inside which the MultiView control is placed. I have enabled the EnablePageMethods="True" of the ScriptManager.

Whenever I am calling the Server Method I am getting:

Object reference not set to an Instance of an Object

function CallScreens(id)  {     // var id,var type     // Call server side function     alert('Hello');     PageMethods.SetScreens("-1","screen",OnCallSumComplete,OnCallSumError,""); } 

The Server Side code is as given below

[System.Web.Services.WebMethod]  public static void SetScreens(string id,string Type) {     try     {         TreeView obj = new TreeView();//Name of my Class         obj.MultiView1.ActiveViewIndex=1;     }     catch (Exception ex)     {         throw ex;     } } 

Answer 1

Are you getting this error because MultiView1 has not been instantiated in the TreeView object? Also, webmethods don’t have access to the page elements because they are treated as static.