DataGridView 密码列（显示为*号）的设置

/// <summary>
        /// 单元格显示格式事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
        {
            // 把第4列显示*号，*号的个数和实际数据的长度相同
            if (e.ColumnIndex == 3)
            {
                if (e.Value != null && e.Value.ToString().Length > 0)
                {
                    e.Value = new string('*',e.Value.ToString().Length);
                }
            }
        }

        /// <summary>
        /// 编辑单元格控件事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            // 编辑第4列时，把第4列显示为*号
            TextBox t = e.Control as TextBox;
            if (t != null)
            {
                if (this.dataGridView1.CurrentCell.ColumnIndex == 3)
                    t.PasswordChar = '*';
                else
                    t.PasswordChar = new char();
            }
        }