check if something is on a list by one argument

I've looking for a way to do this, I created a custom class for the Items stored in the players inventory (a list), but I want to check if the Item is there using its "name" argument so if it is not there add it, and if it is there augment its quantity by +1

I've look into List.Contains but since what I need to compare it to its not of the same class I cant use it.

here the code of the Inventory manager (ignore the comments, they are not mine)

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 // This behaviour script would be attached to the player
 public class InventoryManager : MonoBehaviour {
   // stores items picked up
   private int ItemID;
   public AudioClip[] PotionSounds;
   private List<IItem> itemsInInventory = new List<IItem>();
   void Update() {
         Debug.Log(itemsInInventory[0].name + "_" + itemsInInventory[0].Cantidad);
         if (Input.GetButtonDown("use")== true){
             Use();
             
         }
         if (itemsInInventory[ItemID].Cantidad == 0){
              itemsInInventory.RemoveAt(ItemID);
         }
     // check for use input to use item here, or in OnGUI, and call Use()   
   }
     public void AddItem(GameObject Item){
       // We cast to IItem to match our list type. 
       // We can do this because Potion implements IItem.
       // This means we could store different types of items in the list, 
       // as long as they implement IItem.
         Potion ItemScript = Item.GetComponent<Potion>();
         itemsInInventory.Contains
         
         itemsInInventory.Add(new IItem(Item.name,ItemScript.Cantidad,ItemScript.Icon,ItemScript.PotionValue, ItemScript.PotionParticles,ItemScript.Type));
         }  
         
         
         
         
         
           
         // adds new item to end of list
     
 void Use() {
         if (itemsInInventory[ItemID].Cantidad > 0){
         if (itemsInInventory[ItemID].Type == "Potion"){
     GameObject Player = GameObject.FindGameObjectWithTag("Player");
     Player.SendMessage("AddjustCurrentHealth", itemsInInventory[ItemID].Value);
     Player.audio.PlayOneShot(PotionSounds[(Random.Range(0,PotionSounds.Length))]);
     Instantiate(itemsInInventory[ItemID].Particles, Player.transform.position, Quaternion.identity);
     itemsInInventory[ItemID].Cantidad += -1;
         }
     }
     //if (itemsInInventory.Count > 0) {
       // execute UseItem method of first item in list
       /*itemsInInventory[0].UseItem();
       // remove item from list since it has been used
       itemsInInventory.RemoveAt(0);*/
     
     }
 }

IItem class:

 // Interface, containing only signature (design), not implementation
 using UnityEngine;
 using System.Collections;
 
 public class IItem  {
   // classes that implement Item should define this method
   public string Type;
   public string name;
   public int Cantidad;
   public Texture2D Icon;
   public int Value;
   public GameObject Particles;
     public IItem(string newName, int newCantidad, Texture2D newIcon, int newValue, GameObject newParticles, string newType){
         name = newName;
         Cantidad = newCantidad;
         Icon = newIcon;
         Value = newValue;
         Particles = newParticles;
         Type = newType;
         
         
     }
 }

Thanks