Can constructors be async?

I have a project where I’m trying to populate some data in a constructor:

public class ViewModel
{
    public ObservableCollection<TData> Data { get; set; }

    async public ViewModel()
    {
        Data = await GetDataTask();
    }

    public Task<ObservableCollection<TData>> GetDataTask()
    {
        Task<ObservableCollection<TData>> task;

        //Create a task which represents getting the data
        return task;
    }
}

Unfortunately, I’m getting an error:

The modifier async is not valid for this item

Of course, if I wrap in a standard method and call that from the constructor:

public async void Foo()
{
    Data = await GetDataTask();
}

it works fine. Likewise, if I use the old inside-out way

GetData().ContinueWith(t => Data = t.Result);

That works too. I was just wondering why we can’t call await from within a constructor directly. There are probably lots of (even obvious) edge cases and reasons against it, I just can’t think of any. I’ve also search around for an explanation, but can’t seem to find any.