Rotating to a certain degree and stopping?

I'm a bit new to unity and c# and I can't manage to stop a rotation at a certain degree.

 using UnityEngine;
 using System.Collections;
 
 public class RotateBase : MonoBehaviour {
 
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
         if(Input.GetKey(KeyCode.RightArrow))
             transform.Rotate (Vector3.up * 0.5f);
 
         if (Input.GetKey(KeyCode.LeftArrow))
             transform.Rotate(Vector3.down * 0.5f);
 
         if (transform.rotation.y > 45)
             transform.Rotate (Vector3.up * 0.0f);
 
     }
 }

When I press the left and right arrows it rotates all the ways around. I tried stopping the rotation when it hit 45 degrees but I have no clue how to do it. All I know at the moment is basic C# code so if someone can show me how to make the rotation halt at 45 degrees when I'm pressing the right arrow and 315 degrees when I press the left arrow I would be very greatful. Try to keep it simple if you can please.