How to return IAsyncOperation<TReturn> result?

Question

I want to perform CPU intensive work asynchronously. I thought to use code like this one:

   ....
   updateGUIObj = await setSelectedGUICellValueAsync(arg1, arg2, cssId, isInitializeCbxChecked);
   ....


   public IAsyncOperation<UpdateGUIObj> setSelectedGUICellValueAsync(int arg1, int arg2, String cssId, bool isInitializeCbxChecked)
   {
        updateGUIObj = new UpdateGUIObj();

        ....  // compute intensive work setting "updateGUIObj" 

        return ?????;
    }

How should I write the above return statement?

Answer 1

Returning IAsyncOperation<TResult> is necessary if you're writing a WinRT component. However, I recommend writing the IAsyncOperation<TResult> code just as a simple wrapper around the more natural async/await implementation.

There's an extension method that was written specifically for this scenario:

public IAsyncOperation<UpdateGUIObj> setSelectedGUICellValueAsync(int arg1, int arg2, String cssId, bool isInitializeCbxChecked)
{
  return SetSelectedGuiCellValueAsync(arg1, arg2, cssId, isInitializeCbxChecked).AsAsyncOperation();
}

private async Task<UpdateGUIObj> SetSelectedGuiCellValueAsync(int arg1, int arg2, String cssId, bool isInitializeCbxChecked)
{
  updateGUIObj = new UpdateGUIObj();
  await Task.Run(....);
  return updateGUIObj;
}

Answer 2

You can use async/await pattern and returns Task<> objects instead:

...
var updateGUIObj = await setSelectedGUICellValueAsync(arg1, arg2, cssId, isInitializeCbxChecked);
...

public async Task<UpdateGUIObj> setSelectedGUICellValueAsync(int arg1, int arg2, String cssId, bool isInitializeCbxChecked)
{
    var updateGUIObj = new UpdateGUIObj();

    // .... compute intensive work setting "updateGUIObj" 

    return updateGUIObj;
}