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 > 0)
            {
                foreach (string item in filePaths)
                {
                    var lines = System.IO.File.ReadAllLines(item);
                    Array.ForEach(lines.ToArray(), n => richTextBox1.AppendText(n.ToString() + "\r\n"));
                }
            }
        }