Server Error in '/' Application.

'DropDownList1' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value

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.ArgumentOutOfRangeException: 'DropDownList1' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:


[ArgumentOutOfRangeException: 'DropDownList1' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value]
   System.Web.UI.WebControls.ListControl.PerformDataBinding(IEnumerable dataSource) +1379
   System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e) +408
   System.Web.UI.WebControls.ListControl.PerformSelect() +44
   System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +134
   System.Web.UI.WebControls.ListControl.OnPreRender(EventArgs e) +36
   System.Web.UI.Control.PreRenderRecursiveInternal() +132
   System.Web.UI.Control.PreRenderRecursiveInternal() +227
   System.Web.UI.Control.PreRenderRecursiveInternal() +227
   System.Web.UI.Control.PreRenderRecursiveInternal() +227
   System.Web.UI.Control.PreRenderRecursiveInternal() +227
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3671


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.8.4690.0