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 58:         string server_v2 = Convert.ToString(Request.ServerVariables["SERVER_NAME"]);
Line 59:         int changdu = server_v2.Length;
Line 60:         if (server_v1.Substring(7, changdu) != server_v2)
Line 61:         {
Line 62:              Response.Write("网站维护,暂停上传");

Source File: e:\www\ccgq\www\user\addyz.aspx.cs    Line: 60

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
   pux_addyz.Page_Load(Object sender, EventArgs e) in e:\www\ccgq\www\user\addyz.aspx.cs:60
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +91
   System.Web.UI.Control.LoadRecursive() +74
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207

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