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嗯。。。我也是在园子待了不短时间的人了，一直以来汲取着园友的知识，感觉需要回馈什么。
于是以后有空我都会把一些小技巧小知识写下来，有时候可能会很短甚至很简单，但希望能帮到大家咯。
第一篇文章来说说async 和 await吧。
这是微软关于Async的介绍：http://msdn.microsoft.com/en-us/library/hh156513.aspx
这是await ：http://msdn.microsoft.com/en-us/library/hh156528.aspx
这是综合起来讲：http://msdn.microsoft.com/en-us/library/hh191443.aspx
async和await用起来并不是很难，大部分人是这么用的，微软的sample是这么写的：
private async void StartButton_Click(object sender, RoutedEventArgs e) { // ExampleMethodAsync returns a Task<int>, which means that the method // eventually produces an int result. However, ExampleMethodAsync returns // the Task<int> value as soon as it reaches an await. ResultsTextBox.Text += "\n"; try { int length = await ExampleMethodAsync(); // Note that you could put "await ExampleMethodAsync()" in the next line where // "length" is, but due to when ‘+=‘ fetches the value of ResultsTextBox, you // would not see the global side effect of ExampleMethodAsync setting the text. ResultsTextBox.Text += String.Format("Length: {0}\n", length); } catch (Exception) { // Process the exception if one occurs. } } public async Task<int> ExampleMethodAsync() { var httpClient = new HttpClient(); int exampleInt = (await httpClient.GetStringAsync("http://msdn.microsoft.com")).Length; ResultsTextBox.Text += "Preparing to finish ExampleMethodAsync.\n"; // After the following return statement, any method that‘s awaiting // ExampleMethodAsync (in this case, StartButton_Click) can get the // integer result. return exampleInt; } // Output: // Preparing to finish ExampleMethodAsync. // Length: 53292
上面是微软给的写法，给按钮的响应方法加上async，然后await ExampleMethodAsync，让一个Length变量来接收返回值。
但是其实async和await还有另一种用法：
private async void button_Click(object sender, RoutedEventArgs e) { TB_Result.Text = await exampleAsync(); }
private async Task<string> exampleAsync() { return await Task.Run(() => { WebClient w = new WebClient(); w.DownloadFile("http://provissy.com", "webPage1"); w.DownloadFile("http://microsoft.com", "webPage2"); string a = w.DownloadString("http://microsoft.com"); return a; }); }
Task.Run 和 Lambda表达式，用起来其实更加简单。
在 => { }范围内写任何代码都是异步执行的，因此不用担心某几个语句是否会长时间堵住UI线程。
当然，你不能访问UI线程，否则会抛出异常。
如果不返回值，那就更简单了
private async Task exampleAsync() {
// 用 await exampleAsync(); 来调用即可，会立即返回。 await Task.Run(() => { WebClient w = new WebClient(); w.DownloadFile("http://provissy.com", "webPage1"); w.DownloadFile("http://microsoft.com", "webPage2"); });
}
好了就这么多，以后会尽量写详细点。。。
C# & WPF 随手小计之一 ——初探async await 实现多线程处理
标签：style blog http io ar color os sp for
原文地址：http://www.cnblogs.com/provissy/p/4122112.html
