3、使用 BackgroundWorker
多线程返回值最简单方法是:使用 BackgroundWorker 组件来管理线程,在任务完成时引发事件,然后用事件处理程序处理结果。
小注:
BackgroundWorker 组件用来执行诸如数据库事务、文件下载等耗时的异步操作。
在应用程序中添加一个BackgroundWorker实例,如果用的是VS,可以从工具上直接拖到应用程序:
BackgroundWorker backgroundWorker1 = new BackgroundWorker();
为了开始在后台操作,必须调用BackgroundWorker的RunWorkerAsync()方法,当调用此方时,BackgroundWorker 通过触发DoWork 事件,开始执行后台操作,DoWork 事件的代码是在另一个线程里执行的。
当后台操作完成以后,无论是completed 还是cancelled,则RunWorkerCompleted 事件被触发,通过此方法可以将后台操作的完成结果反馈给用户。
另外,通过RunWorkerCompletedEventArgs实例的Cancelled 属性,以判断是否是Cancel操作使得后台操作终止。
具体demo如下:
using System; using System.Windows.Forms; namespace WindowsFormsApplication1 { public partial class Form2 : Form { public Form2() { InitializeComponent(); } private void Form2_Load(object sender, EventArgs e) { //TransitionalClass tc = new TransitionalClass("xiaoming", 10); //ThreadPool.QueueUserWorkItem(new WaitCallback(TransitionalClass.TestFunction), tc); } private void button1_Click(object sender, EventArgs e) { this.TestArea2(); } private System.ComponentModel.BackgroundWorker BackgroundWorker1 = new System.ComponentModel.BackgroundWorker(); private void TestArea2() { InitializeBackgroundWorker(); AreaClass2 AreaObject2 = new AreaClass2(); AreaObject2.Base = 30; AreaObject2.Height = 40; // Start the asynchronous operation. BackgroundWorker1.RunWorkerAsync(AreaObject2); } private void InitializeBackgroundWorker() { // Attach event handlers to the BackgroundWorker object. BackgroundWorker1.DoWork += new System.ComponentModel.DoWorkEventHandler(BackgroundWorker1_DoWork); BackgroundWorker1.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(BackgroundWorker1_RunWorkerCompleted); } private void BackgroundWorker1_DoWork( object sender, System.ComponentModel.DoWorkEventArgs e) { //在执行DoWork 事件时,DoWorkEventArgs 实例的Result 属性,返回值到用户;在RunWorkerCompleted 事件里,RunWorkerCompletedEventArgs 实例的Result 属性接收值; AreaClass2 AreaObject2 = (AreaClass2)e.Argument; // Return the value through the Result property. e.Result = AreaObject2.CalcArea(); } private void BackgroundWorker1_RunWorkerCompleted( object sender, System.ComponentModel.RunWorkerCompletedEventArgs e) { // Access the result through the Result property. double Area = (double)e.Result; MessageBox.Show("The area is: " + Area.ToString()); } } } |
demo代码来自MSDN:点击打开链接
参考文章:点击打开链接
4、如果不如返回值的时候,应该怎么优雅的写呢?匿名函数啊
FunctionClass类新增,测试函数如下:
public static void TestFunction2(string name, int age)
{
//内部处理省略
}
调用如下:
private void Form1_Load(object sender, EventArgs e)
{
Thread t1 = new Thread(new ThreadStart(delegate
{
FunctionClass.TestFunction2("eee", 5);
}));
t1.Start();
}
小注:
如果通过WCF来调用的话,应该把起线程的函数放到服务端,如果放到客户端,很容易因为WCF客户端的时间限制,造成造成主程序的莫名崩溃。
崩溃的原因主要是客户端wcf响应时间是有限制。