c# - GridView doesn't display data

I'm a beginner in C# and Xamarin. I have this code but I don't know what's wrong with it, that doesn't display data in gridview.

this is the code of my activity:

public class MenuFoodActivity : Activity
{
string dpPath = Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "HotelDb.db3");

GridView gv;
ArrayAdapter adapter;
JavaList tvShows = new JavaList();


protected override void OnCreate(Bundle savedInstanceState)

{
    base.OnCreate(savedInstanceState);
    SetContentView(Resource.Layout.MenuFood);
    gv = FindViewById(Resource.Id.gridViewMenu);
    adapter = new ArrayAdapter(this, Android.Resource.Layout.SimpleListItem1, tvShows);            
    Retrieve();

}
private void Retrieve()
{

    var db = new SQLiteConnection(dpPath);
    var data = db.Table();
    var data1 = (from values in data
                 select new FoodTable
                 {
                     Shenase = values.Shenase,
                     Types = values.Types,
                     Names = values.Names,
                     Costs = values.Costs


                 }).ToList();

    tvShows.Add(data1);
    if (tvShows.Size() > 0)
    {
        gv.Adapter = adapter;
    }
    else
    {


        Toast.MakeText(this, "not found.", ToastLength.Short).Show();
    }
}
}

and this one is for axml file:

android:minWidth="25px"

android:minHeight="25px"
android:layout_width="wrap_content"
android:layout_height="200dip"
android:id="@+id/gridViewMenu"
android:background="#aaa"
android:layout_marginTop="10dip" />

every thing seems fine and I can enter to the if statment but there's nothing in my gridview. Anyone knows what's the problem with this code?
Thanks beforehand.

I've tried to use

List tvShows = new List();
JavaList tvShows = new JavaList();
JavaList tvShows = new JavaList();

but they didn't work for me.