I'm building my very first game with XNA and i'm trying to get my sprite to run. Everything is working fine for the first sprite. E.g : if I go right(D) my sprite is looking right , if I go left(A) my sprite is looking left and if I don't touch anything my sprite is the default one. Now what I want to do is if the sprite goes Right, i want to alternatively change sprites (left leg, right leg, left leg etc..) xCurrent is the current sprite drawn xRunRight is the first running Sprite and xRunRight1 is the one that have to exchange with xRunRight while running right. This is what I have now :

    protected override void Update(GameTime gameTime)
    {
        float timer = 0f;
        float interval = 50f;
        bool frame1 = false ;
        bool frame2 = false;
        bool running = false;

        KeyboardState FaKeyboard = Keyboard.GetState();
        // Allows the game to exit
        if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
            this.Exit();


            if ((FaKeyboard.IsKeyUp(Keys.A)) || (FaKeyboard.IsKeyUp(Keys.D)))
            {
                xCurrent = xDefault;
            }

            if (FaKeyboard.IsKeyDown(Keys.D))
            {

                timer += (float)gameTime.ElapsedGameTime.TotalMilliseconds;
                if (timer > interval)
                {
                    if (frame1)
                    {
                        xCurrent = xRunRight;
                        frame1 = false;
                    }
                    else
                    {
                        xCurrent = xRunRight1;
                        frame1 = true;

                    }
                }

                xPosition += xDeplacement;


            }

Any ideas...? I've been stuck on this for a while.. Thanks in advance and let me know if you need any other part from the code.