2D raycast for Unity3D

raycast.cs

RaycastHit2D hit = Physics2D.Raycast((Vector2)transform.position, direction, length, layerMask);

// check hit in direction
if (hit.collider != null) {
    // we hit something check what it is
    if (hit.collider.gameObject.CompareTag("wall")) {
        // we hit a wall so don't translate in this direction
    }
}