如何在c＃中asynchronous调用任何方法
有人可以告诉我一小段代码演示如何在c＃中asynchronous调用一个方法吗？
如果使用action.BeginInvoke（），则必须在某处调用EndInvoke ，否则框架必须在堆上保存asynchronous调用的结果，导致内存泄漏。
如果你不想用async / await关键字跳转到C＃5，那么你可以在.Net 4中使用Task Parallels库。它比使用BeginInvoke / EndInvoke要好得多，忘记asynchronous作业：
using System.Threading.Tasks; ... void Foo(){} ... new Task(Foo).Start(); 如果你有调用这个参数的方法，你可以使用lambda来简化调用，而不必创build委托：
void Foo2(int x, string y) { return; } ... new Task(() => { Foo2(42, "life, the universe, and everything");}).Start();
我非常确定（但肯定不是肯定的），C＃5asynchronous/等待语法只是任务库周围的语法糖。
从.Net 4.5开始，你可以使用Task.Run来简单地开始一个动作：
void Foo(string args){} ... Task.Run(() => Foo("bar"));
http://blogs.msdn.com/b/pfxteam/archive/2011/10/24/10229468.aspx
这是一个办法：
// The method to call void Foo() { } Action action = Foo; action.BeginInvoke(ar => action.EndInvoke(ar), null);
当然，如果方法具有不同的签名，则需要用另一种types的委托来replaceAction
查看MSDN文章asynchronous编程与asynchronous和等待，如果你能负担得起玩新的东西。 它被添加到.NET 4.5。
链接示例代码片段（本身来自此MSDN示例代码项目 ）：
// Three things to note in the signature: // - The method has an async modifier. // - The return type is Task or Task<T>. (See "Return Types" section.) // Here, it is Task<int> because the return statement returns an integer. // - The method name ends in "Async." async Task<int> AccessTheWebAsync() { // You need to add a reference to System.Net.Http to declare client. HttpClient client = new HttpClient(); // GetStringAsync returns a Task<string>. That means that when you await the // task you'll get a string (urlContents). Task<string> getStringTask = client.GetStringAsync("http://msdn.microsoft.com"); // You can do work here that doesn't rely on the string from GetStringAsync. DoIndependentWork(); // The await operator suspends AccessTheWebAsync. // - AccessTheWebAsync can't continue until getStringTask is complete. // - Meanwhile, control returns to the caller of AccessTheWebAsync. // - Control resumes here when getStringTask is complete. // - The await operator then retrieves the string result from getStringTask. string urlContents = await getStringTask; // The return statement specifies an integer result. // Any methods that are awaiting AccessTheWebAsync retrieve the length value. return urlContents.Length; }
引用：
如果
AccessTheWebAsync在调用GetStringAsync和等待其完成之间没有任何工作，那么可以通过在以下单个语句中调用和等待来简化代码。
string urlContents = await client.GetStringAsync();
更多细节在链接 。
public partial class MainForm : Form { Image img; private void button1_Click(object sender, EventArgs e) { LoadImageAsynchronously("http://media1.santabanta.com/full5/Indian%20%20Celebrities(F)/Jacqueline%20Fernandez/jacqueline-fernandez-18a.jpg"); } private void LoadImageAsynchronously(string url) { /* This is a classic example of how make a synchronous code snippet work asynchronously. A class implements a method synchronously like the WebClient's DownloadData(…) function for example (1) First wrap the method call in an Anonymous delegate. (2) Use BeginInvoke(…) and send the wrapped anonymous delegate object as the last parameter along with a callback function name as the first parameter. (3) In the callback method retrieve the ar's AsyncState as a Type (typecast) of the anonymous delegate. Along with this object comes EndInvoke(…) as free Gift (4) Use EndInvoke(…) to retrieve the synchronous call's return value in our case it will be the WebClient's DownloadData(…)'s return value. */ try { Func<Image> load_image_Async = delegate() { WebClient wc = new WebClient(); Bitmap bmpLocal = new Bitmap(new MemoryStream(wc.DownloadData(url))); wc.Dispose(); return bmpLocal; }; Action<IAsyncResult> load_Image_call_back = delegate(IAsyncResult ar) { Func<Image> ss = (Func<Image>)ar.AsyncState; Bitmap myBmp = (Bitmap)ss.EndInvoke(ar); if (img != null) img.Dispose(); if (myBmp != null) img = myBmp; Invalidate(); //timer.Enabled = true; }; //load_image_Async.BeginInvoke(callback_load_Image, load_image_Async); load_image_Async.BeginInvoke(new AsyncCallback(load_Image_call_back), load_image_Async); } catch (Exception ex) { } } protected override void OnPaint(PaintEventArgs e) { if (img != null) { Graphics grfx = e.Graphics; grfx.DrawImage(img,new Point(0,0)); } }
