One of my favorite features in Mango is the ability for developers to let users pin a deep linking secondary tile to their start screen. It’s a simple concept but really opens up a lot of new opportunities for apps-within-an-app, shortcuts to oft-used functionality, plus many other innovations.

In 4th & Mayor, I use these to allow people to pin places to the start, and also to check-in a lot quicker. In my current released version, I actually found out after-the-fact about a remote URI bug, and wanted to share my notes on this.

If you’re looking for the basic reference on this deep-linking feature, do refer to the “Create, Delete, and Update Tiles for Windows Phone” entry on MSDN.

What’s the issue with remote URIs?

As best I can tell, the situation is: adding a secondary tile with a relative URI (pointing to an app’s content, such as SomeImage.png, that is packaged within the .Xap) is OK, and that secondary tile will always be present.

However, if you use a remote URI (such as a dynamically generated background image, or from a database or social network), that secondary tile is only present for that current device’s uptime: if you restart the device (or the battery dies, etc.), when you come back, the secondary tiles will no longer be present.

Users should still be able to re-pin any of their favorite secondary tiles to the start screen again. However, it turns out there is a bug here unfortunately: the secondary tile is still present in the ActiveTiles collection, and the OS seems to believe that it is still there, even though it is not.

The workaround is to search for the existing identical secondary tile and delete it, before re-pinning it, in your apps. This does mean that it’s not possible to tell whether a secondary tile with a remote URI is truly pinned or not – it will look pinned in the ActiveTiles collection but the user will not actually have the item pinned.

Using a remote URI

If you just use a remote URI (absolute), you will experience one-time pin ability; after that, and a device restart, it won’t be possible to re-pin the same page without first deleting the entry.

Using a remote URI, working around re-pin issues

Here is the code I’ve used to workaround these issues, effectively deleting the tile first, and re-pinning, only when using an absolute URI:

private void OnPinButtonPressed(object sender, RoutedEventArgs e)
{
    var backgroundImage = new Uri("http://tiles.4thandmayor.com/CrownBackground.png", UriKind.Absolute);

    var tile  = ShellTile.ActiveTiles
        .FirstOrDefault(x => x.NavigationUri == NavigationService.CurrentSource);

    // Only if this is a remote background image URI do we need to
    // delete and re-pin the secondary tile.
    if (tile != null && backgroundImage.IsAbsoluteUri)
    {
        tile.Delete();

        var newTile = new StandardTileData
        {
            BackgroundImage = backgroundImage,
            Title = "Secondary Tile",
        };

        ShellTile.Create(NavigationService.CurrentSource, newTile);
    }
}

9/29/11 1:40 PM PST note: It’s been pointed out to me that I don’t know how to code. The code above will re-pin, but not initially pin. A little more boolean logic is needed. I’ll try and update later, but the concept remains.

Hope this helps.