code:

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;


namespace SomethingAwful.Example
{
   public class Tile
   {
      public static Vector2 Size = new Vector2(128, 64);
      public static Vector2 SizeHalf = Size / 2;

      public static Texture2D TextureOne;
      public static Texture2D TextureTwo;
      public static Texture2D TextureThree;

      public static int OffsetX
      {
         get { return (int) (Size.X / 2); }
      }

      public static int OffsetY
      {
         get { return (int) (Size.Y); }
      }
   }

   public class Tilemap
   {
      private int[,] _tiles;

      public Tilemap()
      {
         _LoadTiles("blah");
      }

      public void Draw(SpriteBatch spriteBatch)
      {
         for (int x = 0; x < 10; x++)
         {
            for (int y = 0; y < 10; y++)
            {
               int tile = this._tiles[x, y];

               var position = new Vector2((y-x) * Tile.SizeHalf.X, (x+y) * Tile.SizeHalf.Y);
               position += new Vector2(Tile.SizeHalf.X * 10, 0.0f); // replaceme with world x,y translation

               var texture = tile == 0 ? Tile.TextureOne : (tile == 1 ? Tile.TextureTwo : Tile.TextureThree);
               position.Y -= texture.Height / 2;

               //spriteBatch.Draw(texture, position, Color.White);
               spriteBatch.Draw(texture, position, null, Color.White, 0.0f, Vector2.Zero, 0.5f, SpriteEffects.None, 0.0f);
            }
         }
      }

      private void _LoadTiles(string path)
      {
         // for now just fake it.
         this._tiles = new int[10,10]
                       {
                          { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 },
                          { 1, 1, 0, 0, 0, 0, 0, 0, 0, 1 },
                          { 1, 0, 0, 0, 0, 0, 0, 0, 0, 1 },
                          { 1, 0, 0, 2, 1, 2, 1, 0, 0, 1 },
                          { 1, 0, 0, 1, 1, 1, 1, 0, 0, 1 },
                          { 1, 0, 0, 2, 1, 2, 2, 0, 0, 1 },
                          { 1, 0, 0, 1, 1, 2, 2, 0, 0, 1 },
                          { 1, 0, 0, 0, 0, 0, 0, 0, 0, 1 },
                          { 1, 0, 0, 0, 0, 0, 0, 0, 1, 1 },
                          { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 },
                       };
      }
   }
}