Unity drag drop 2d

using System.Collections;
using System.Collections.Generic;
using UnityEngine;


public class DragDrop : MonoBehaviour {
    public string SpawnGroupName = "SpawnGroup";
    public float ScaleSpeed = 1;
    //public GameObject DragObj;
    public bool OnClick = false;
    private GameObject PlantNew;

    public List<GameObject> PlantList;

    private GameObject SpawnGroup;

    Vector3 MousePosition()
    {
        Vector3 MousePos = Input.mousePosition;
        MousePos = Camera.main.ScreenToWorldPoint(MousePos);
        MousePos = new Vector3(MousePos.x, MousePos.y, 0f);
        return MousePos;
    }

    void Start () {
        SpawnGroup = new GameObject(SpawnGroupName);

    }
    void Update () {

        //OnClick = false;
        Vector3 MousePos = MousePosition();
        bool IsFlipped = false;
        if (Input.GetKey("f"))
        {
            IsFlipped = true;
        }
        if (Input.GetMouseButton(0))
        {
            if (OnClick == false) {
                int ListIndex = Random.Range(0, PlantList.Count);
                //Debug.Log(ListIndex);
                PlantNew = (GameObject)Instantiate(
                PlantList[ListIndex],
                MousePos + new Vector3(0,0, Random.Range(-0.1f, 0.1f)),
                transform.rotation);

                PlantNew.transform.parent = SpawnGroup.transform;
                OnClick = true;
            }

            if (PlantNew)
            {
                //PlantNew.transform.position = MousePos;

                Vector3 diff = MousePos - PlantNew.transform.position;
                float MagScale = Vector3.Distance(MousePos, PlantNew.transform.position) * ScaleSpeed;
                //Debug.Log(MagScale);
                float AngleInRadians = Mathf.Atan2(diff.y, diff.x);
                float AngleInDegrees = AngleInRadians * Mathf.Rad2Deg;
                PlantNew.transform.rotation = Quaternion.Euler(0.0f, 0.0f, AngleInDegrees);
                if (IsFlipped)
                {
                    PlantNew.transform.localScale = new Vector3(-MagScale, MagScale, 1);
                }
                else
                {
                    PlantNew.transform.localScale = new Vector3(MagScale, MagScale, 1);

                }

            }



        }
        if (Input.GetMouseButtonUp(0))
        {
            OnClick = false;
        }
    }
}