Winform开发遇到的问题之TextBox与ChenckedListBox

1.代码块：

       //CheckListBox:名称AreaList,TextBox:名称txt_Area[重点：控件的事件要选对]
        /// <summary>
        /// CheckedListBox与TetxBox组合使用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void AreaList_SelectedIndexChanged(object sender, EventArgs e)
        {
            string str = string.Empty;
            for (int i = 0; i < AreaList.Items.Count; i++)
            {
                if (AreaList.GetItemChecked(i))
                {
                    if (str == string.Empty)
                    {
                        str = AreaList.GetItemText(
         AreaList.Items[i]);
                    }
                    else
                    {
                        str = str + "," + AreaList.
         GetItemText(AreaList.Items[i]);
                    }
                }
            }
            txt_Area.Text = str;
        }

2.效果图：