C#控件刷新

int count = 0;
int success_count = 0;
foreach (string gen in fn_gen)
{
    //MessageBox.Show(gen);
    Bitmap Bi = new Bitmap(gen);  //使用打开的图片路径创建位图对像
    Image Image = Bi;
    if (Image.Width >= 170 && Image.Height >= 200)
    { 
        string destinationFile = result + gen.Substring(gen.LastIndexOf(@""), gen.Length - gen.LastIndexOf(@""));
        bool isrewrite = true; // true=覆盖已存在的同名文件,false则反之
        System.IO.File.Copy(gen, destinationFile, isrewrite);
        success_count++;
        this.Txt_Count.Refresh();
        this.Txt_Count.Text = success_count.ToString() + "/" + count.ToString();
        Application.DoEvents();// Application.DoEvents()的作用：处理所有的当前在消息队列中的Windows消息。
        System.Threading.Thread.Sleep(100);
    }
    count++;
    Bi = null;
    System.GC.Collect();
}