SQL DataReader: System.IndexOutOfRangeException ASP.Net

District

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.IndexOutOfRangeException: District Source Error: 

Line 80:                 TxtMT8.Text = _dr["Service8"].ToString();
Line 81:                 DDL2.Items.FindByValue(_dr["Region"].ToString()).Selected = true;
Line 82: DdlDistrict.Items.FindByValue(_dr["District"].ToString()).Selected = true;

i am sure i have district column in my table

thanks