How to pass path to plugin?

Hi guys, I'm writing my first plugin, it is a Windows Phone 8 one, how can I send a the path of a texture to a function so it can access the texture?

I want it to update the live tile and couldn't found sample codes.

Edit:

The plugin is a DLL that will update the Live Tile of the app, for this I must supply to it some parameters, but the DLL will be running device code, even if it is still C# it is not Unity C# anymore, so only have access to classes available in the Windows Phone 8 SDK.

Here is the DLL code:

 public static void Update(string title, int count, string imgPath)
         {
             ShellTile PinnedTile = ShellTile.ActiveTiles.First();
 
             FlipTileData updatedTileData = new FlipTileData
             {
                 Title = title,
                 Count = count,
                 BackTitle = "de traz",
                 BackgroundImage = new Uri(imgPath)
             };
 
             PinnedTile.Update(updatedTileData);
         }

And this is my code in Unity

  LiveTilesPlugin.UpdateTile.Update("Title App", 55, "doge.jpg");

What should I pass to the imgPath parameter so it can access the file? Just the file name resulted in crash.

Edit 2:

Still with error using

 path = System.IO.Path.Combine(Application.streamingAssetsPath, "doge.png");

The result string on the Emulator is the following: "C:/Data/Programs/{7545C7EA-396B-4ECA-9306-5E095280BB60}/Install/Data/StreamingAssets\\doge.png"

Are these double \\ correct?