How to Update IconicTile & LockScreen defined by WMAppManifest.xml - windows-phone-8

Question

I'm trying to create an IconicTile for Windows Phone 8. I've defined with VS2012 the type of Tile Template to TemplateIconic and added a Tile Title and two images for small and medium.
If I pin my app to the start screen, I can choose between small and medium tiles like expected.
Now I want to update the IconicTile I defined in my WMAppManifest.xml. As I understand IconicTile, it needs to be updated in code and will also update the LockScreen icon and count, if I defined one. I've added a DeviceLockImageURI and this Extensions:
<Extensions>
<Extension ExtensionName="LockScreen_Notification_IconCount" ConsumerID="{111DFF24-AA15-4A96-8006-2BFF8122084F}" TaskID="_default"/>
<Extension ExtensionName="LockScreen_Notification_TextField" ConsumerID="{111DFF24-AA15-4A96-8006-2BFF8122084F}" TaskID="_default" />
</Extensions>
First question: Is this ConsumerID always the same or which ID is it?
To update the IconicTile I've defined in WMAppManifest.xml, I need to get hold of any pinned Tiles of my Application on the screen. I've read a lot of tutorials explaining how to add tiles manually from your application, but I only want to use the tile I've defined in WMAppManifest.xml. Therefore all tutorials recommended to get the current active Tile with this code:
ShellTile.ActiveTiles.FirstOrDefault();
ActiveTiles is an IEnumeration and only offers me: Equals, GetEnumerator, GetHashCode, GetType and ToString
Second question: What am I missing here? Does FirstOrDefault only work for FlipTiles or CycleTiles? I only want to use the IconicTile!
So I'm stuck at identifying the current active IconicTile on the screen, so that I can use an IconicTileData object to update the count or text of the IconicTile. What am I missing here?

Answer 1

For the first question:
I've seen a Tile ID when you create an IconicTile from Xml:
<wp:Tile Id="[Tile ID]" Template="IconicTile">
Maybe it is this ID? Otherwise I'll go with allways the same static ID, as there is no documentation on how to create this ID.
For the second question:
I've found the error: I was missing
using System.Linq;
This using enables access to the Linq Methods necessary to use FirstOrDefault or similar commands. I was mislead by
using System.Xml.Linq;
which is definitevly not the same Linq class ;)