Sample Backpack

BackpackManager

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

public class BackpackManager : MonoBehaviour {
	public List<ItemData.ItemAttribute> _BackpackItem = new List<ItemData.ItemAttribute>();
	public List<ItemData.ItemAttribute> m_BackpackItem {
		get { 
			return _BackpackItem; 
		}
		set {
			_BackpackItem = value;
		}
	}

	private BackpackUIManager m_BackpackUIManager;
	// Use this for initialization
	void Start () {
		m_BackpackUIManager = GetComponent <BackpackUIManager>();

		AddItemCount(1,3);
		AddItemCount(6,3);
		AddItemCount(6,-3);
	}
	
	void AddItemCount(int itemUid, int addCount){
		int itemIndex = m_BackpackItem.FindIndex(_item => _item.uid==itemUid);
		if (itemIndex <0){
			int theLastIndex = m_BackpackItem.Count;
			AddItemToList(itemUid, theLastIndex);
			m_BackpackItem[theLastIndex].count += addCount;
			// Send Add Item UI
			m_BackpackUIManager.AddItemToList(m_BackpackItem[theLastIndex]);
		}else{
			m_BackpackItem[itemIndex].count += addCount;
			// When Count <=0 RemoveItem
			if (m_BackpackItem[itemIndex].count <= 0){
				m_BackpackUIManager.RemoveItemFormList(m_BackpackItem[itemIndex]);
				m_BackpackItem.Remove(m_BackpackItem[itemIndex]);
			}
		}
	}

	void AddItemToList(int itemUid, int theLastIndex){
		ItemData.ItemAttribute newItemData = GetItemData(itemUid);
		m_BackpackItem.Add(new ItemData.ItemAttribute(){uid = itemUid});
	}

	ItemData.ItemAttribute GetItemData(int itemUid){
		ItemData.ItemAttribute _itemData = new ItemData.ItemAttribute()
		{
			uid = itemUid,
			name = "None Name",
			image = null,
		};
		return _itemData;
	}

}

BackpackUIManager

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

public class BackpackUIManager : MonoBehaviour {
	[System.Serializable]
	public class _BackpackItem{
		public int ItemUid;
		public GameObject ItemButton;
	}
	public List<_BackpackItem> m_BackpackItem = new List<_BackpackItem>();

	public GameObject ItemButtonPerfabs;
	public Transform BackpackList;

	// Update is called once per frame
	public void AddItemToList (ItemData.ItemAttribute itemInfo) {
		GameObject theItemButton = Instantiate(ItemButtonPerfabs) as GameObject;
		theItemButton.transform.SetParent(BackpackList,true);
		m_BackpackItem.Add(new _BackpackItem(){ItemUid = itemInfo.uid, ItemButton = theItemButton});
	}
	public void RemoveItemFormList(ItemData.ItemAttribute itemInfo){
		int theItemUid = m_BackpackItem.FindIndex(_Item => _Item.ItemUid == itemInfo.uid);
		Destroy(m_BackpackItem[theItemUid].ItemButton);
		m_BackpackItem.Remove(m_BackpackItem[theItemUid]);
	}
}

ItemData

using UnityEngine;
using System.Collections;

public class ItemData{
	[System.Serializable]
	public class ItemAttribute{
		public int _uid;
		public Sprite _image;
		public string _name;
		public int _count;
		public string _explanation;
		public int uid{
			get { 
				return _uid; 
			}
			set {
				_uid = value;
			}
		}
		public Sprite image{
			get { 
				return _image; 
			}
			set {
				_image = value;
			}
		}
		public string name{
			get { 
				return _name; 
			}
			set {
				_name = value;
			}
		}
		public int count{
			get { 
				return _count; 
			}
			set {
				_count = value;
				if (_count <=0){
					_count = 0;
				}
			}
		}
		public string explanation{
			get { 
				return _explanation; 
			}
			set {
				_explanation = value;
			}
		}
	}
}