Server Error in '/' Application.

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

Line 28:     {
Line 29:         string abo = "";
Line 30:         if (Request.QueryString["num"].ToString() == "1")
Line 31:         {
Line 32:             if (num == 1)

Source File: d:\web\ynzzyt\Left.ascx.cs    Line: 30

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
   Left.ABO(Int32 num) in d:\web\ynzzyt\Left.ascx.cs:30
   ASP.left_ascx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in d:\web\ynzzyt\Left.ascx:3
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +149
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +54
   System.Web.UI.Control.Render(HtmlTextWriter writer) +39
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +94
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +343
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +64
   ASP.about_aspx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\708a2e40\b5bad168\App_Web_bzb3mo2n.14.cs:0
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +149
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +54
   System.Web.UI.Control.Render(HtmlTextWriter writer) +39
   System.Web.UI.Page.Render(HtmlTextWriter writer) +49
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +94
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +343
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +64
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +6017


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1