Help with shift-RUN on a Simple FPS controller

Hello, I am new to unity and created a simple script for just movement which works. Now I want to add running with ‘‘left shift’’ key but I cant get it to work. Here is my script with the line for running which I cant get to work: Hope someone can help me out with this.

using UnityEngine;
using System.Collections;

public class Movement : MonoBehaviour {

public float playerSpeed = 8.0f;
public float RunSpeed = 10.0f;

// Use this for initialization
void Start () {


}

// Update is called once per frame
void Update () {
	transform.Translate (Vector3.right * Input.GetAxis("Horizontal") * playerSpeed * Time.deltaTime);
	transform.Translate (Vector3.forward * Input.GetAxis("Vertical") * playerSpeed * Time.deltaTime);
	if (Input.GetButtonDown("KeyCode.LeftShift")){
	playerSpeed = RunSpeed; 
            {



}

}

You had to use GetKeyDown instead of GetButtonDown, GetButtonDown only use for Input Manager

Change from this line of code

if (Input.GetButtonDown("KeyCode.LeftShift")){

To this

if (Input.GetKeyDown(KeyCode.LeftShift)){

Btw, if you wish to hold and run, maybe you should try with GetKey

if (Input.GetKey(KeyCode.LeftShift)){

thanks alot!! this got me somewhere it works but keeps sprinting after touching shift 1 time so now i have to trigger it to stop running when releasing the button.