static class DrapDropExtend
{
    public static void SimpleDrapDrop<T>(this Control c, string dataformat, Action<T> hanlder) where T : class
    {
        c.AllowDrop = true;
        c.DragEnter += (s, e) =>
            {
                if (e.Data.GetDataPresent(dataformat))
                    e.Effect = DragDropEffects.Copy;
                else
                    e.Effect = DragDropEffects.None;
            };

        c.DragDrop += (s, e) =>
            {
                var data = e.Data.GetData(dataformat) as T;
                hanlder(data);
            };
    }

    public static void SimpleDrapDrop(this Control c, Action<DragEventArgs> enterHanlder, Action<DragEventArgs> dropHanlder)
    {
        c.AllowDrop = true;
        c.DragEnter += (s, e) => enterHanlder(e);
        c.DragDrop += (s, e) => enterHanlder(e);
    }

    public static void SimpleDrapDrop(this Control c, DragEventHandler enterHanlder, DragEventHandler dropHanlder)
    {
        c.AllowDrop = true;
        c.DragEnter += enterHanlder;
        c.DragDrop += dropHanlder;
    }
}

public Form1()
{
    InitializeComponent();
    this.SimpleDrapDrop<string>(DataFormats.Text, x => this.Text = x);
}