Autocomplete textbox in wpf with c# code

private void PopulateNames(object sender, PopulatingEventArgs e)
        {
            try
            {
                conn.Open();
                List<string> types = new List<string>();
                string accountQuery = "SELECT EmpName FROM EmpDetails WHERE EmpName LIKE '" + e.Parameter + "%'";
                SqlDataReader accountTypes = null;
                SqlCommand query = new SqlCommand(accountQuery, conn);
                accountTypes = query.ExecuteReader();
                while (accountTypes.Read())
                {
                    types.Add(accountTypes["EmpName"].ToString());                    
                }
                AutoCompleteBox accountType = (AutoCompleteBox)sender;
                accountType.ItemsSource = types;
                accountTypes.Close();
                conn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);

                // Close the DB if there was an error.
                if (conn.State == ConnectionState.Open)
                    conn.Close();
            }
        }