c# 代理异步 回调

Class1.StuDele _dele = null;

public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
Class1 c1 = new Class1();

AsyncCallback callBack = new AsyncCallback(UploadComplete);

_dele += new Class1.StuDele(Do1);

IAsyncResult iResult = _dele.BeginInvoke("hha", callBack, null);
}

private void UploadComplete(IAsyncResult results)
{
System.Diagnostics.Debug.WriteLine("12345");
if (this.InvokeRequired)
{
AsyncCallback callback = new AsyncCallback(UploadComplete);
this.BeginInvoke(callback, results);
return;
}
}

string Do1(string str)
{
MessageBox.Show(str + "_1");

return "Haha Excuted Do1!";
}