Thread th = new Thread(delegate() {
　　append();
});
th.IsBackground = true;
th.Start();

//在append方法里面需要调用前台控件

public void append(){

　　// ... 业务处理　　

　　this.Invoke(new flushMessage(showMessage), new object[] { row["Code"].ToString(), res });
}

//委托flushMessage和方法showMessage签名必须一致
private delegate void flushMessage(String id, String res);
private void showMessage(String id,String res)
{
if (res == "true")
{
txtMsg.Text += "\t\t\t\t" + id + "\t\t\t\t导入成功\r\n";
}
else
{
txtMsg.Text += "\t\t\t\t" + id + "\t\t\t\t\t导入失败\r\n";
}
}