Server Error in '/' Application.

Sequence contains no elements

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.InvalidOperationException: Sequence contains no elements

Source Error:


Line 27:                 int GI = int.Parse(Request.QueryString["tag"]);
Line 28: 
Line 29:                 var tag = (from r in db.SubGroups
Line 30:                            where (r.Id == GI & r.Group.Title == "تگ")
Line 31:                            select r).First();

Source File: c:\HostingSpaces\imenpower.com\httpdocs\tag.aspx.cs    Line: 29

Stack Trace:


[InvalidOperationException: Sequence contains no elements]
   System.Linq.Enumerable.First(IEnumerable`1 source) +417
   tag.Page_Load(Object sender, EventArgs e) in c:\HostingSpaces\imenpower.com\httpdocs\tag.aspx.cs:29
   System.Web.UI.Control.OnLoad(EventArgs e) +108
   System.Web.UI.Control.LoadRecursive() +90
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1533


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.8.4700.0