Unity 3D picking target position on terrain with mouse c#

// Unity 3D example picking a target position on a terrain using the mouse cursor using ray casting

using UnityEngine;
using System.Collections;

public class MouseTarget : MonoBehaviour {

    void Update ()
    {
        Ray ray = camera.ScreenPointToRay(Input.mousePosition);
        RaycastHit hit;
        if(Terrain.active.collider.Raycast(ray,out hit,Mathf.Infinity))
        {
            transform.position = hit.point
        }
    }
}