Net2.0實現帶參數的線程

如果你想為一個線程傳入變數你怎麼辦?

ThreadStart可不支援帶參數的方法.所以你無法使用Thread來啟動一個帶參數的方法..

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 過在.Net1.0下,你可以通過Delegate的非同步呼叫來實現.現在在.Net2.0下提供了ParameterizedThreadStart 這麼一個Delegate.它和ThreadStart 的不同就在於可以擁有一個object類型的參數.也就是說你可以通過它來使用Thread類以啟動一個線程並傳入參數, 和Java很象了,不錯的新功能.

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);
        }
    }
}

還有一個新增的類BackgroundWorker,可以用於啟動後台線程,並在後台計算結束後及時調用主線程的方法.
一個常見的應用就是在DataGrid中載入資料的時候.因為從資料庫中載入DataSet比較耗時, 所以你可以使用
BackgroundWorker來進行載入, 當DataSet構造好後就立即綁定上DataGrid. 其實該功能同樣可以通過Delegate的非同步呼叫實現不過BackgroundWorker用起來更方便一些.

//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();

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