Making a GUI Object stay in screen using ViewportToWorldPoint

So, the code below works but it moves the Panel gui to the bottom left corner
Here's the code:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class dragablePanel : MonoBehaviour {
6.  
7.     float OffsetX;
8.     float OffsetY;
9.     // Use this for initialization
10.     void Start () {
11.      
12.     }
13.  
14.     // Update is called once per frame
15.     void Update () {
16.      
17.     }
18.  
19.     public void BeginDrag()
20.     {      
21.         OffsetX = transform.position.x - Input.mousePosition.x;
22.         OffsetY = transform.position.y - Input.mousePosition.y;
23.     }
24.  
25.     public void OnDrag()
26.     {
27.         // Old Working without border!?
28.         //transform.position = new Vector3(OffsetX + Input.mousePosition.x, OffsetY + Input.mousePosition.y);
29.  
30.         float dist = (OffsetY - Camera.main.transform.position.y);
31.         float leftLimitation = Camera.main.ViewportToWorldPoint(new Vector3(0, 0, dist)).x;
32.         float rightLimitation = Camera.main.ViewportToWorldPoint(new Vector3(1, 0, dist)).x;
33.  
34.         float upLimitation = Camera.main.ViewportToWorldPoint(new Vector3(0, 0, dist)).z;
35.         float downLimitation = Camera.main.ViewportToWorldPoint(new Vector3(0, 1, dist)).z;
36.  
37.         float tempx = Mathf.Clamp(OffsetX + Input.mousePosition.x, upLimitation, downLimitation);
38.         float tempy = Mathf.Clamp(OffsetY + Input.mousePosition.y, leftLimitation, rightLimitation);
39.         transform.position = new Vector3(tempx, tempy);
40.     }
41. }
42.