Was young

 首先AllowDrop 属性为true，然后要在DragEnter事件里这么写

        private void Form1_DragEnter(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.FileDrop)) e.Effect = DragDropEffects.Link;
            else e.Effect = DragDropEffects.None;
        }
这样就可以得到拖到文件的路径了，任意文件
        private void Form1_DragDrop(object sender, DragEventArgs e)
        {
            string[] filePath = (string[])e.Data.GetData(DataFormats.FileDrop);
            foreach (string file in filePath )
            {
                   //file就是单个文件路径
            }
        }