最近在学习citrix的xenserver6.2的源代码，发现多处用到System.Threading命名空间下的ThreadPool.QueueUserWorkItem方法：
public static bool QueueUserWorkItem(WaitCallback callBack, object state);
publicstaticbool QueueUserWorkItem(WaitCallback callBack);
参数WaitCallback 本身是一个delegate，它在System.Threading命名空间中的定义如下：
[ComVisible(true)] public delegate void WaitCallback(object state);
于是问题来了，该如何给QueueUserWorkItem传参呢？以下是我遇到的一些方式：
1,直接传delegate。（不明白object o去了哪里？）
ThreadPool.QueueUserWorkItem(delegate
{
for (int i = 0; i < 20 && TargetNode.Nodes.Count == 0; i++)
{
Thread.Sleep(100);
}
MainWindowCommandInterface.Invoke(delegate { TargetNode.Expand(); });
});
2,直接传方法名。
ThreadPool.QueueUserWorkItem(WaitForReboot, connection);
private void WaitForReboot(object o)
{
}
3,用delegate构造一个WaitCallback。
ThreadPool.QueueUserWorkItem(new WaitCallback(delegate(Object o)
{
ClientFillRectangle(0, 0, DesktopSize.Width, DesktopSize.Height, Color.Black);
}), null);
4,用含一个object类型的方法Connect构造一个WaitCallback。
ThreadPool.QueueUserWorkItem(new WaitCallback(Connect), new KeyValuePair<VNCGraphicsClient, Exception>(vncClient, null));
private void Connect(object o)
{
}
5，WaitCallback类型的delegate。
ThreadPool.QueueUserWorkItem((WaitCallback)delegate(object o)
{
// Sleep a short time before closing the splash
Thread.Sleep(500);
Program.Invoke(Program.MainWindow, Program.CloseSplash);
});
6,直接传Lambda表达式。
ThreadPool.QueueUserWorkItem(o =>
{
Program.Invoke(Program.MainWindow, () =>
{
PerformStorageSystemScan();
if (systemsAfter.Count > systemsBefore.Count)
{
// the new item should be selected
. comboBoxStorageSystem.SelectedItem = systemsAfter.Find(ss => !systemsBefore.Contains(ss));
comboBoxStorageSystem.DroppedDown = true;
}
});
});
