page level error checking for update / delete / insert and general errors

put in main aspx.
Protected Sub Page_Error(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Error
        ' BEGIN - catching errors due to referential integrity constraints
        ' getting the exception
        Dim objErr As Exception = Server.GetLastError().GetBaseException()
        Dim tempMsg As String
        Dim tempStrAndErrCompDELETE As Boolean
        Dim tempStrAndErrComp As Boolean
        ' getting the message from objerr (the real exception raised)
        Dim tempErrorMessage As String
        tempErrorMessage = objErr.Message.ToString()
        ' comparing variables for violations
        tempStrAndErrCompDELETE = tempErrorMessage.Contains("DELETE")
        tempStrAndErrComp = tempErrorMessage.Contains("")
        ' looking for DELETE violation
        If (tempStrAndErrCompDELETE = True) Then
            tempMsg = "This is a non-critical error. There was an error during DELETE operation. This was because the record you tried to delete is already being used. If a record is already being used in another table then deleting it would also delete its entry from there and that would create null references. For further explanation of this please contact Saad Hashmi, Asst. IT Programmer." _
                      + vbCrLf + " Error: " + tempErrorMessage
            Server.Transfer("TempErrorAdmin.aspx?request_tempMsg=" + tempMsg)
            ' looking for GENERAL violation
        ElseIf (tempStrAndErrComp = True) Then
            tempMsg = "This is a critical general error. For further explanation of this please contact Saad Hashmi, Asst. IT Programmer." _
                    + " Error: " + tempErrorMessage
            Server.Transfer("TempErrorAdmin.aspx?request_tempMsg=" + tempMsg)
        End If
        ' clearing the server error raised
        Server.ClearError()
    End Sub
make a TempErrorAdmin.aspx page and place code...

Partial Class TempErrorAdmin
    Inherits System.Web.UI.Page
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim tmp_lbl_ErrorLabel As Label
        tmp_lbl_ErrorLabel = CType(FindControl("ErrorLabel"), Label)
        tmp_lbl_ErrorLabel.Text = Request.QueryString("request_tempMsg")
    End Sub
    Protected Sub btn_back_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn_back.Click
        ' If the querystring had a DELETE in it then transfer it back
        ' to requesting page on press of BACK BUTTON.
        ' However if querystring had something other than DELETE then transfer
        ' to default.aspx.
        ' This is because if querystring was something other than DELETE (or a ref. integrity violation)
        ' then the requesting page will transfer it back to error page since its a critical error.
        Dim temp_PreviousPage As String
        Dim tempStrAndErrCompDELETE As Boolean
        Dim tempStrAndErrComp As Boolean
        'Dim tmp_ContentPlaceHolder As ContentPlaceHolder = CType(Master.FindControl("ContentPlaceHolder1"), ContentPlaceHolder)
        Dim tmp_lbl_ErrorLabel As Label = CType(FindControl("ErrorLabel"), Label)
        tmp_lbl_ErrorLabel.Text = Request.QueryString("request_tempMsg")
        ' comparing variables for violations
        tempStrAndErrCompDELETE = tmp_lbl_ErrorLabel.Text.Contains("DELETE")
        tempStrAndErrComp = tmp_lbl_ErrorLabel.Text.Contains("")
        ' looking for DELETE violation
        If (tempStrAndErrCompDELETE = True) Then
            temp_PreviousPage = Request.UrlReferrer.ToString
            Response.Redirect(temp_PreviousPage)
            ' looking for GENERAL violation
        ElseIf (tempStrAndErrComp = True) Then
            temp_PreviousPage = "Default.aspx"
            Response.Redirect(temp_PreviousPage)
        End If
    End Sub
End Class