private void RemoveElement(Balance substractListElement)
 {
     foreach (Balance bal in _balanceList)
     {
         if (bal.BalanceName == substractListElement.BalanceName)
         {
             bal.Quantity -= substractListElement.Quantity;
         }
     }
 }
 private void AddElement(Balance addListElement)
 {
     foreach (Balance bal in _balanceList)
     {
         if (bal.BalanceName == addListElement.BalanceName)
         {
             bal.Quantity += addListElement.Quantity;
         }
     }
 }