namespace WindowsFormsApplication1{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();            richTextBox1.AllowDrop = true;            richTextBox1.DragEnter += new DragEventHandler(richTextBox1_DragEnter);            richTextBox1.DragDrop += new DragEventHandler(richTextBox1_DragDrop);        }        private void richTextBox1_DragEnter(object sender, DragEventArgs e)        {            if (e.Data.GetDataPresent(DataFormats.FileDrop))            {                e.Effect = DragDropEffects.Link;            }            else            {                e.Effect = DragDropEffects.None;            }        }        private void richTextBox1_DragDrop(object sender, DragEventArgs e)        {            Array arrayFileName = (Array)e.Data.GetData(DataFormats.FileDrop);            string strFileName = arrayFileName.GetValue(0).ToString();            StreamReader sr = new StreamReader(strFileName,System.Text.Encoding.Default);            richTextBox1.Text = sr.ReadToEnd();            sr.Close();        }    }}