用csharp实现的截屏功能，鼠标拖拽捕获要截屏的区域，截屏，并保存成选择的图片格式。 可以用鼠标反向拖拽关闭程序。-Achieved with csharp screenshot function, drag the mouse to capture screen shots of the area, screen shots, and save the image into the selected format. Drag with the mouse can turn off the