Unity Drag.

_dragAndDrop.gif

OrtographicDrag.cs

using UnityEngine;
using UnityEngine.EventSystems;

public class OrtographicDrag: MonoBehaviour, IDragHandler
{
    private Camera _mainCamera;
    public float DistanceToCamera;

    public void OnDrag(PointerEventData eventData)
    {
        var screenPosition = new Vector3(eventData.position.x, eventData.position.y, DistanceToCamera);

        var worldPosition = _mainCamera.ScreenToWorldPoint(screenPosition);
        transform.position = worldPosition;
    }
    // Use this for initialization
    private void Awake()
    {
        _mainCamera = Camera.main; //Cache the camera, micro optimization.
    }
}

PerspectiveDrag.cs

using UnityEngine;
using UnityEngine.EventSystems;

public class PerspectiveDrag: MonoBehaviour,  IDragHandler
{
    private Camera _mainCamera;
    private Plane _plane;
    [SerializeField] float Offset = 0;

    public void OnDrag(PointerEventData eventData)
    {
        var ray = _mainCamera.ScreenPointToRay( eventData.position);
        float enter;
        if( _plane.Raycast( ray, out enter ) )
        {
            var rayPoint = ray.GetPoint(enter);
            transform.position = rayPoint;
        }
    }

    // Use this for initialization
    private void Awake()
    {
        _plane = new Plane( Vector3.up, -Offset );
        _mainCamera = Camera.main; //Cache the camera, micro optimization.
    }

    //If someone changes the offset.
    private void OnValidate()
    {
        _plane = new Plane( Vector3.up, -Offset );
    }
}

ThePackage.unitypackage

UIDrag.cs

using System;
using UnityEngine;
using UnityEngine.EventSystems;

public class UIDrag: MonoBehaviour, IDragHandler
{
    public void OnDrag(PointerEventData eventData)
    {
        transform.position = eventData.position;
    }




}