Combined script file output failed unexpectedly in c# ashx

Question

<%@ WebHandler Language="C#" Class="CombineScriptsHandler" %>

  using System;

 using System.Web; 

using AjaxControlToolkit; 

 public class CombineScriptsHandler : IHttpHandler 

{     /// <summary>     /// ProcessRequest implementation outputs the combined script file     /// </summary>     /// <param name="context"></param>   

using System; using System.Web; 
using AjaxControlToolkit;  
public class CombineScriptsHandler : IHttpHandler 
{ 
public void ProcessRequest(HttpContext context)
 { 
if (!ToolkitScriptManager.OutputCombinedScriptFile(context)) 
{ throw new InvalidOperationException("Combined script file output failed unexpectedly.");//error here
 } 
} 
public bool IsReusable { 
get { 
return true; }
 }
 }