Net2.0 的新线程 ParameterizedThreadStart &BackgroundWorker

如果你想为一个线程传入变量你怎么办?  

ThreadStart可不支持带参数的方法.所以你无法使用Thread来启动一个带参数的方法.. 

 

ThreadStart myThreadDelegate = new ThreadStart(ThreadMethod);
//public delegate void ThreadStart();  u can't pass a Parameter
Thread myThread = new Thread(myThreadDelegate);
myThread.Start();  //myThread.Start(o); Wrong!

不过在.Net1.0下,你可以通过Delegate的异步调用来实现 
http://www.cnblogs.com/idior/articles/100666.html 

现在在.Net2.0下提供了 ParameterizedThreadStart 这么一个Delegate.它和ThreadStart 的不同就在于可以拥有一个object类型的参数.也就是说你可以通过它来使用Thread类以启动一个线程并传入参数, 和Java很象了,不错的新功能. 

 

using System;
using System.Threading;
namespace ParameterizedThreadStartTest
{
class Program
{
static void Main(string[] args)
{
ParameterizedThreadStart myParameterizedThreadDelegate = new ParameterizedThreadStart(ThreadMethod);
Thread myThread = new Thread(myParameterizedThreadDelegate);
object o = "hello";
myThread.Start(o);
}
private static void ThreadMethod(object o)
{
string str = o as string;
Console.WriteLine(str);
}
}
}

还有一个新增的类 BackgroundWorker,可以用于启动后台线程,并在后台计算结束后及时调用主线程的方法.一个常见的应用就是在DataGrid中载入数据的时候.因为从数据库中载入DataSet比较耗时, 所以你可以使用 BackgroundWorker来进行载入, 当DataSet构造好后就立即绑定上DataGrid. 其实该功能同样可以通过Delegate的异步调用实现不过 BackgroundWorker用起来更方便一些. 

 

//1. Instantiate a BackgroundWorker instance:
BackgroundWorker myDataWorker = new BackgroundWorker();
//2. Setup a DoWork delegate that does the work that you want to be done on the background thread.

myDataWorker.DoWork += new DoWorkEventHandler(delegate(object o, DoWorkEventArgs workerEventArgs)
{
workerEventArgs.Result = new XXXDAL().GetData();
}
);
//3. Setup a RunWorkerCompleted delegate that handles updating your UI with the data recieved on the background thread.
myDataWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(delegate(object o, RunWorkerCompletedEventArgs workerEventArgs)
{
DataSet data = (DataSet) workerEventArgs.Result;
this.dataGrid.DataSource = data;
}
);
//4.Run your worker by calling the RunWorkerAsync() method on your BackgroundWorker instance.
myDataWorker.RunWorkerAsync();