金科玉律:不要在UI线程上执行耗时的操作;不要在除了UI线程之外的其他线程上访问UI控件!
NET1.1的BeginInvoke异步调用,需要准备3个方法:功能方法GetWebsiteLength,结果方法DownloadComplete,呼叫方法BeginInvoke!
但很不幸,在UI线程之外访问UI线程控件!调用失败。线程同步必须在线程所属进程的公共区域保留同步区,以此实现线程间的通讯。
二、C#2.0引入了BackgroundWorker,从而极大的简化了线程间通讯。
三、C#4.0引入的async和await关键字,使得一切变得如此简单!
async和await关键字
using System; using System.Windows.Forms; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace AsyncDemo { class MyForm:Form { Label lblInfo; Button btnCaculate; public MyForm() { lblInfo = new Label { Location = new System.Drawing.Point(10, 20), Text = "Length" }; btnCaculate = new Button { Location = new System.Drawing.Point(10, 50), Text = "GetLength" }; btnCaculate.Click += DisplayWebsiteLength; AutoSize = true; this.Controls.Add(lblInfo); this.Controls.Add(btnCaculate); } async void DisplayWebsiteLength(object sender,EventArgs e) { lblInfo.Text = "Fetching..."; using (System.Net.Http.HttpClient client = new System.Net.Http.HttpClient()) { //string text = await client.GetStringAsync("http://flaaash.cnblogs.com"); //lblInfo.Text = text.Length.ToString(); Task<string> task = client.GetStringAsync("http://www.sina.com"); string contents = await task; lblInfo.Text = contents.Length.ToString(); } } static void Main(string[] args) { Application.Run(new MyForm()); } } }
BackgroundWorker
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace AsyncDemo { class BackWorker : Form { Label lblInfo; Button btnCaculate; System.ComponentModel.BackgroundWorker worker; BackWorker() { lblInfo = new Label { Location = new System.Drawing.Point(10, 20), Text = "Length" }; btnCaculate = new Button { Location = new System.Drawing.Point(10, 50), Text = "GetLength" }; btnCaculate.Click += (o, e) => { worker.RunWorkerAsync(); }; this.Controls.Add(lblInfo); this.Controls.Add(btnCaculate); worker = new System.ComponentModel.BackgroundWorker(); worker.DoWork += (o, e) => { System.Net.WebClient client = new System.Net.WebClient(); string contents = client.DownloadString("http://www.sina.com"); e.Result = contents.Length; }; worker.RunWorkerCompleted += (o, e) => lblInfo.Text = e.Result.ToString(); } public static void MainTest(string[] args) { Application.Run(new BackWorker()); } } }
时间: 2024-11-05 22:12:50