虚拟异步方法

Question

我想定义未在基类异步一个虚拟方法，但它是异步的派生类和呼叫者使用委托调用它（实际上它是由一个按钮来激活一个ICommand屏幕上）我该怎么做。

public class BaseClass 
{ 
    BIONESSBindingCommand mLogoffCommand; 

    public ICommand LogoffCommand 
    { 
     get 
     { 
      if (mLogoffCommand == null) 
      { 
       mLogoffCommand = new BIONESSBindingCommand(
        Param => Logoff(), //Command DoWork 
        Param => true); //Always can execute 
      } 

      return mLogoffCommand; 
     } 
    } 

    public virtual Task Logoff() 
    { 
     DoLogoff(); 
     return null; //??? 
    } 
} 

public class DerivedClass : BaseClass 
{ 
    public override async Task Logoff() 
    { 
     await SomeWoAsyncWork(); 
     base.Logoff(); //Has warninngs 
    } 
} 

Answer 1

呼叫Task.FromResult得到完成Task。另外，await它在派生类中（这将启用错误传播）。

public class BaseClass 
{ 
    public virtual Task Logoff() 
    { 
    DoLogoff(); 
    return Task.FromResult(false); 
    } 
} 

public class DerivedClass : BaseClass 
{ 
    public override async Task Logoff() 
    { 
    await SomeWoAsyncWork(); 
    await base.Logoff(); 
    } 
}