C++异步执行顺序 task.wait() error

Question

void ImagesShow::TimerShaft::GetImagePropertys(Platform::String^ folderName)
{	   		
  create_task(KnownFolders::PicturesLibrary->GetFolderAsync(folderName)).then([this](StorageFolder^ folder)
 {
    if (folder != nullptr)
    {			
	create_task(folder->GetFilesAsync()).then( [folder](IVectorView<StorageFile^>^ files) 
	{
	  std::for_each(begin(files), end(files), [files](  StorageFile^ file)
          {					
	   if (file)
	       {    
                    create_task(file->Properties->GetImagePropertiesAsync()).then([file]( ImageProperties^ ImgProperty  )		
                    {							
                        //（1）Do something  								
                    });						 
                     create_task(file->GetThumbnailAsync(ThumbnailMode::SingleItem, 1024, ThumbnailOptions::UseCurrentScale)).then([file](StorageItemThumbnail^ thumbnail)				             
                      {							
                        //（2）Do something  		              		
                      });					 
                }
           });						
        }); 			
      }
      //（3）Do something 
   });	
}

大家好，请问一下怎么等待（1）（2）执行完再执行（3）呢？？

Thanks

Answer 1

void ImagesShow::TimerShaft::GetImagePropertys(Platform::String^ folderName)
{	   		
  create_task(KnownFolders::PicturesLibrary->GetFolderAsync(folderName)).then([this](StorageFolder^ folder)
 {
    if (folder != nullptr)
    {			
	create_task(folder->GetFilesAsync()).then( [folder](IVectorView<StorageFile^>^ files) 
	{
	  std::for_each(begin(files), end(files), [files](  StorageFile^ file)
          {					
	   if (file)
	       {    
                    create_task(file->Properties->GetImagePropertiesAsync()).then([file]( ImageProperties^ ImgProperty  )		
                    {							
                        //（1）Do something  								
                    });						 
                     create_task(file->GetThumbnailAsync(ThumbnailMode::SingleItem, 1024, ThumbnailOptions::UseCurrentScale)).then([file](StorageItemThumbnail^ thumbnail)				             
                      {							
                        //（2）Do something  		              		
                      });					 
                }
           });						
        }); 			
      }
      //（3）Do something 
   });	
}

大家好，请问一下怎么等待（1）（2）执行完再执行（3）呢？？

Thanks

求助啊！