ItemDragHandler.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
public class ItemDragHandler : MonoBehaviour, IDragHandler,IDropHandler,IBeginDragHandler
{

    public static GameObject itemDragging;
    Transform StartParent;

    Vector3 startPosition;
    public void OnBeginDrag(PointerEventData eventData)
    {
        itemDragging = gameObject;
        startPosition = transform.position;
        StartParent = transform.parent;
        //GetComponent<CanvasGroup>().blocksRaycasts = false;
    }

    public void OnDrag(PointerEventData eventData)
    {
        transform.position = Input.mousePosition;
    }

    public void OnDrop(PointerEventData eventData)
    {
        itemDragging = null;
        //GetComponent<CanvasGroup>().blocksRaycasts = true;
        if (transform.parent == StartParent)
        {
            transform.position = startPosition;
        }

    }

   
}