I need help fixing error on a C# script

Hello I am trying to make a c# code for my platformer. I already have code for moving left and right, but I am trying to make one that will make the character jump. This is what I have now, but it says
"error CS0102: An object reference is required to access non static member ‘UnityEngine.Transform.TransformDirection(UnityEngine.Vector3)’ "

using UnityEngine;

using System.Collections;

public class jump_controller : MonoBehaviour {

public float speed = 6.0F;

public float jumpSpeed = 8.0F;

public float gravity = 20.0F;

private Vector3 moveDirection = Vector3.zero;

void Update() {

    CharacterController controller = GetComponent<CharacterController>();

    if (controller.isGrounded) {

        moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));

        moveDirection = transform.TransformDirection(moveDirection);

        moveDirection *= speed;

        if (Input.GetButton("Jump"))

            moveDirection.y = jumpSpeed;
    moveDirection.y -= gravity * Time.deltaTime;

    controller.Move(moveDirection * Time.deltaTime);


Please keep in mind this is my 2nd script and I don’t know much about this so please keep it simple.

This script compiles fine for me. The error you list is one you would get if you use ‘Transform.TransformDirection()’ with an upper case ‘t’ to start rather than ‘transform.TransformDirection()’. And the part of the error you list has an upper case ‘T’.