WF4.0 基础篇 (二十四) Async Activity

 

例子下载:

http://files.cnblogs.com/foundation/AsyncCodeActivitySample.rar

 

项目说明:

Async Activity

Async的意思是异步,但有一点一定要注意,不能按字面理解,该Activity的功能是以同步的方式调用异步方法的Activity

建议看过[WF4.0 基础篇 (十三) InvokeMethod 调用方法 ]后,再看本文

 

 

类名	System.Activities.AsyncCodeActivity
文件	System.Activities.dll
结构说明	继承 Activity 是一个 abstract类 override 了 [CacheMetadata方法] 提供两个 abstract方法 [BeginExecute],[EndExecute]
功能说明	AsyncCodeActivity的主要目的是实现当Activity中有异步操作时,如何等待有异步完成后才向下执行的问题,也就是说如何将并行变为串行

 

 

类名	System.Activities.AsyncCodeActivity<TResult>
文件	System.Activities.dll
结构说明	继承 Activity<TResult> 是一个 abstract类 override 了 [CacheMetadata方法] 提供两个 abstract方法 [BeginExecute],[EndExecute]
功能说明	与AsyncCodeActivity,可以在[EndExecute]方法中return 返回值

 

 

 

 

 

 

 

例1:AsyncCodeActivity

等待[BeginXXX]方法(以FileStream.BeginWrite为例)

 

myAsyncWriteFile	public sealed class myAsyncWriteFile: AsyncCodeActivity { public InArgument<string> fileName { set; get; }   public InArgument<string> fileData { set; get; }   protected override IAsyncResult BeginExecute(AsyncCodeActivityContext context, AsyncCallback callback, object state) { string fn = context.GetValue(fileName); string fd = context.GetValue(fileData);   System.Console.WriteLine("开始写入文件"); FileStream fileStream = File.Open(fn, FileMode.Create); context.UserState = fileStream; byte[] bytes = UnicodeEncoding.Unicode.GetBytes(fd); IAsyncResult r = fileStream.BeginWrite(bytes, 0, bytes.Length, callback, state); return r; }   protected override void EndExecute(AsyncCodeActivityContext context, IAsyncResult result) { System.Threading.Thread.Sleep(5000);   FileStream file = (FileStream)context.UserState; file.EndWrite(result); file.Flush(); file.Close(); System.Console.WriteLine("写入文件完成"); } }
流程
宿主	WorkflowInvoker.Invoke(new myAsyncWriteFileWorkflow());
结果

 

例2:AsyncCodeActivity<TResult>

等待[BeginXXX]方法(以FileStream.BeginWrite为例)

 

myAsyncWriteFileByResult	public sealed class myAsyncWriteFileResult : AsyncCodeActivity<string> { public InArgument<string> fileName { set; get; }   public InArgument<string> fileData { set; get; }   protected override IAsyncResult BeginExecute(AsyncCodeActivityContext context, AsyncCallback callback, object state) { string fn = context.GetValue(fileName); string fd = context.GetValue(fileData);   System.Console.WriteLine("开始写入文件"); FileStream fileStream = File.Open(fn, FileMode.Create); context.UserState = fileStream; byte[] bytes = UnicodeEncoding.Unicode.GetBytes(fd); IAsyncResult r = fileStream.BeginWrite(bytes, 0, bytes.Length, callback, state); return r; }   protected override string EndExecute(AsyncCodeActivityContext context, IAsyncResult result) { System.Threading.Thread.Sleep(5000);   FileStream file = (FileStream)context.UserState; file.EndWrite(result); file.Flush(); file.Close(); System.Console.WriteLine("写入文件完成"); return "写入成功"; }     }
流程
宿主	WorkflowInvoker.Invoke(new myAsyncWriteFileByResultWorkflow());
结果