C# 文件拖放

private void FormMain_DragEnter(object sender, DragEventArgs e)
        {
            if(e.Data.GetDataPresent(DataFormats.FileDrop))
            {
                txtSourceBin.Text = "";
                txtGenerateBin.Text = "";
                e.Effect = DragDropEffects.Link;
            }
            else
            {
                e.Effect = DragDropEffects.None;
            }

        }

        private void FormMain_DragDrop(object sender, DragEventArgs e)
        {
            string filePath= ((System.Array)e.Data.GetData(DataFormats.FileDrop)).GetValue(0).ToString();        
            if (filePath.Substring(filePath.LastIndexOf(".")).ToLower() == ".bin")
            {
                txtSourceBin.Text = filePath;
                SetDefaultFileName(txtSourceBin.Text);
            }
        }