C# 窗体打开拖动到窗体的文件

         private void Form3_DragEnter(object sender, DragEventArgs e)
         {
             if (e.Data.GetDataPresent(DataFormats.FileDrop))
             {
                 e.Effect = DragDropEffects.All;
             }
             else
             {
                 e.Effect = DragDropEffects.None;
             }

         }

         private void Form3_DragDrop(object sender, DragEventArgs e)
         {
             string[] filePaths = (string[])e.Data.GetData(DataFormats.FileDrop, false);
             if (null != filePaths && filePaths.Length > )
             {
                 foreach (string item in filePaths)
                 {
                     var lines = System.IO.File.ReadAllLines(item);
                     Array.ForEach(lines.ToArray(), n => richTextBox1.AppendText(n.ToString() + "\r\n"));
                 }
             }
         }