Let's say you have the following block controller:

public class MyBlockController : BlockController<MyBlock>
{
    public override ActionResult Index(MyBlock currentBlock)
    {
        ...
        return PartialView(model);
    }
}

Create new base controller:

public abstract class BaseController<TContentData> : ActionControllerBase, IRenderTemplate<TContentData>, IRenderTemplate where TContentData : IContentData
{
 
}

Your block controller should look like this:

public class MyBlockController : BaseController<MyBlock>
{
    public async Task<ActionResult> Index(MyBlock currentBlock)
    {
        ...
        await DoAwaitableOperation();
        ...
        return PartialView(model);
    }
}

Hope this helps!

Hi Decan

Thanks for your reply., 

However I seem to have found a solution. 

Hi Muhammad, your first try should work. This is how I have implemented async task -> 

public async Task<ActionResult> Index(ArticlePage currentPage)
{

}

I inherit PageController. It works. You have the identical code, right?

Thanks guys

I have managed to solved it without hassle.  I used Andreas' approach which seems most easy.