我们知道，缺省的编辑框仅支持剪接板的剪切、拷贝、粘贴操作，不支持拖放操作，本程序扩展了CEdit类为CDragEdit类，并再实现了CDEDropTarget和CDEDataSource，实现编辑之间拖放文本的操作-We know that the default edit box only support the shear plate editing, copy, paste operation, does not support drag and drop, this program extends the CEdit category CDragEdit category, and again and realized CDEDropTarget CDEDataSource. editor drag and drop text between the operation