nearby_search.cs

private void btnGeoWithAddress_Click(object sender, EventArgs e)
{
   search_view = base.LayoutInflater.Inflate(Resource.Layout.search_alert_layout, null);
   AlertDialog.Builder builder = new AlertDialog.Builder(this);
   builder.SetView(search_view);
   builder.SetTitle("Search Location");
   builder.SetNegativeButton("Cancel", (sender, arg) => { builder.Dispose(); });
   search_view.FindViewById<Button>(Resource.Id.btnSearch).Click += btnSearchClicked;
   alert = builder.Create();
   alert.Show();
}

private void btnSearchClicked(object sender, EventArgs e)
{
   string searchText = search_view.FindViewById<TextView>(Resource.Id.txtSearch).Text;
   GeocodeManager geocodeManager = new GeocodeManager(this);
   geocodeManager.NearbySearch(CurrentPosition, searchText);
}