using System.Web.Mvc; 

public class JsonpResult : JsonResult 
{ 
  
  public string Callback { get; set; } 

  public JsonpResult() 
  { 
    JsonRequestBehavior = JsonRequestBehavior.AllowGet; 
  } 

  public override void ExecuteResult(ControllerContext context) 
  { 
    var httpContext = context.HttpContext; var callback = Callback; 
    if(string.IsNullOrWhiteSpace(callback)) callback = httpContext.Request["callback"]; 
    
    httpContext.Response.Write(callback + "("); base.ExecuteResult(context); httpContext.Response.Write(");"); 
  } 
}