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 |  |
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