Calling Awaitable Methods in Property Accessor [Windows Store Apps/Metro Apps]

Question

I have a custom class (to simplify stuff, I have stripped down the codes): ``` public class AlbumItem { public StorageFile AlbumThumbnail { get; set;} } ``` When I bind this to a ListView: ``` ``` The `Image`'s source is set to `AlbumSource`, as I have thought to implement `AlbumSource` as a `Get`-only property: ``` public class AlbumItem { public StorageFile AlbumThumbnail { get; set;} public BitmapImage AlbumSource { get { BitmapImage bmp = new BitmapImage(); bmp.SetSource(await AlbumThumbnail.OpenReadAsync()); return bmp; } } } ```…

Accepted Answer

IMHO property accessors should always return almost immediately. Long running operations should not execute inside a property accessor as this can have significant perfromance impacts because of the widely held assumption that an accessor is basically a variable read operation (i.e. properties can be accessed a lot, in loops, not cached for subsequent access etc).

I'd do something like this:

```
private async Task SetAlbumSourceAsync()
{
    bmp = new BitmapImage();
    var source = await AlbumThumbnail.OpenReadAsync();
    bmp.SetSource(source);
    RaisePropertyChanged("AlbumSource");
}

BitmapImage bmp;
public BitmapImage AlbumSource
{
    get
    {
        if (bmp == null) // might need a better sync mechanism to prevent reentrancy but you get the idea
            SetAlbumSourceAsync();

return bmp;
    }
}
```

Calling Awaitable Methods in Property Accessor [Windows Store Apps/Metro Apps]

Solution

Problem