grpc/examples/csharp/HelloworldXamarin/HelloworldXamarin.Android/Assets/AboutAssets.txt

Any raw assets you want to be deployed with your application can be placed in
this directory (and child directories) and given a Build Action of "AndroidAsset".

These files will be deployed with your package and will be accessible using Android's
AssetManager, like this:

public class ReadAsset : Activity
{
    protected override void OnCreate (Bundle bundle)
    {
        base.OnCreate (bundle);

        InputStream input = Assets.Open ("my_asset.txt");
    }
}

Additionally, some Android functions will automatically load asset files:

Typeface tf = Typeface.CreateFromAsset (Context.Assets, "fonts/samplefont.ttf");