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 21:         if (!Page.IsPostBack)
Line 22:         {
Line 23:             num1 = Request.QueryString["num"].ToString();
Line 24:             //加載QQ
Line 25:             DataSet dsft1 = part.SelectAll("Information_Table");

Source File: d:\web\ynzzyt\Product.aspx.cs    Line: 23

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
   Product.Page_Load(Object sender, EventArgs e) in d:\web\ynzzyt\Product.aspx.cs:23
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +37
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +95
   System.Web.UI.Control.OnLoad(EventArgs e) +145
   System.Web.UI.Control.LoadRecursive() +134
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3419


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