Server Error in '/' Application.

Input string was not in a correct format.

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.FormatException: Input string was not in a correct format.

Source Error:

Line 21:     protected void Page_Load(object sender, EventArgs e)
Line 22:     {
Line 23:         newsid1 = int.Parse(Request.QueryString["newsid"] ?? "") - 1;
Line 24:         newsid2 = int.Parse(Request.QueryString["newsid"] ?? "") + 1;
Line 25:         //shownews();

Source File: s:\Bnt_NanJingLongxiao\readnews.aspx.cs    Line: 23

Stack Trace:

[FormatException: Input string was not in a correct format.]
   System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +14292453
   System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) +305
   readnews.Page_Load(Object sender, EventArgs e) in s:\Bnt_NanJingLongxiao\readnews.aspx.cs:23
   System.Web.UI.Control.LoadRecursive() +71
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3178

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34280