How can i have var in c#

 var forward = transform.TransformDirection(Vector3.forward);
 var input = Input.GetAxis("Vertical");
 function Update(){
 transform.position += forward * input * Time.deltaTime;
 transform.Rotate( 0 , Input.GetAxis("Horizontal") * 45 * Time.deltaTime , 0 );
 }

I want conver javascript to c# but i have some errors:

 using UnityEngine;
 using System.Collections;
 
 public class TransformDirectionx : MonoBehaviour {
     float forward = transform.TransformDirection(Vector3.forward);
     float input = Input.GetAxis("Vertical");
 
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
         transform.position += forward * input * Time.deltaTime;
         transform.Rotate( 0 , Input.GetAxis("Horizontal") * 45 * Time.deltaTime , 0 );
     
     }
 }