Capture Primary Key Violation Error

Hello,,

I need to capture the primary key violation error:

        If e.CommandName = "Insert" Then
            Dim EmployeeIDTextBox As TextBox = CType(dvContact.FindControl("EmployeeIDTextBox"), TextBox)
            Dim LastName As TextBox = CType(dvContact.FindControl("LastName"), TextBox)
            Dim FirstName As TextBox = CType(dvContact.FindControl("FirstName"), TextBox)     

            Using cmdAdd As New System.Data.SqlClient.SqlCommand

                'Establish connection to the database connection
                Dim sqlcon As New SqlClient.SqlConnection(ConfigurationManager.ConnectionStrings("eConnString").ToString)

                'Open connection
                sqlcon.Open()

                'Pass opened connection (see above) to the command object
                cmdAdd.Connection = sqlcon

                'Using "With/End With" pass content to columns from text objects and datatime variables (see above)
                With cmdAdd
                    .Parameters.Add(New SqlClient.SqlParameter("@EmployeeID", EmployeeIDTextBox.Text))
                    .Parameters.Add(New SqlClient.SqlParameter("@LastName", LastName.Text))
                    .Parameters.Add(New SqlClient.SqlParameter("@FirstName", FirstName.Text))
         
                    'Establish the type of commandy object
                    .CommandType = CommandType.Text

                    'Pass the Update nonquery statement to the commandText object previously instantiated
                    .CommandText = "INSERT INTO ATTEmployee(EmployeeID, LastName, FirstName & _
                         "VALUES (@EmployeeID, @LastName, @FirstName)"
                End With


                'Execute the nonquerry via the command object
                cmdAdd.ExecuteNonQuery() '<==Need to capture primaryKey violation, give user message, cancel insert,return to detailView ReadOnly

               'I haven't figured out the correct code to capture the primary key violation

               EDITMsg.Text="You can not insert an duplicate record.  Try Again."

                'Close the sql connection
                sqlcon.Close()
            End Using
        End If

 

Thank you for your help