Insert only if new else update in BindingList

Hi I have a custom BindingList Containing Products with the following information

string ProductID
int Amount;

How would I make it possible to do the following.

ProductsList.Add(new Product("ID1", 10));
ProductsList.Add(new Product("ID2", 5));
ProductsList.Add(new Product("ID2", 2));

The list should then contain 2 Products

ProductID = "ID1"   Amount = 10
ProductID = "ID2"   Amount = 7;

So It workes kind of like a Shopping Cart

Im looking at the AddingNew Event and override void InsertItem(int index, T item)

But I could really need a little he开发者_高级运维lp getting started

i really don't know why you require this custom list as there are many good collections in the .net library but i have tried something below.

 public class ProductList
{
   public string ProductID {get;set;}
   public int Amount {get;set;}
}

public class MyBindingList<T>:BindingList<T> where T:ProductList
{

    protected override void InsertItem(int index, T item)
    {

        var tempList = Items.Where(x => x.ProductID == item.ProductID);
        if (tempList.Count() > 0)
        {
           T itemTemp = tempList.FirstOrDefault();
           itemTemp.Amount += item.Amount;


        }
        else
        {
            if (index > base.Items.Count)
            {
                base.InsertItem(index-1, item);
            }
            else
                base.InsertItem(index, item);

        }

    }

    public void InsertIntoMyList(int index, T item)
    {
        InsertItem(index, item);
    }



}

and in the client code where you can use this list.

        ProductList tempList = new ProductList() { Amount = 10, ProductID = "1" };
        ProductList tempList1 = new ProductList() { Amount = 10, ProductID = "1" };
        ProductList tempList2 = new ProductList() { Amount = 10, ProductID = "2" };
        ProductList tempList3 = new ProductList() { Amount = 10, ProductID = "2" };

        MyBindingList<ProductList> mylist = new MyBindingList<ProductList>();

        mylist.InsertIntoMyList(0, tempList);
        mylist.InsertIntoMyList(1, tempList1);
        mylist.InsertIntoMyList(2, tempList2);
        mylist.InsertIntoMyList(3, tempList);
        mylist.InsertIntoMyList(4, tempList1);
        mylist.InsertIntoMyList(0, tempList3);

Creating your own collection is rarely the right choice - I would favor containment rather than inheritance in this case. Something like

class ProductsList
{
    private readonly SortedDictionary<string, int> _products 
                                   = new Dictionary<string,int>();

    public void AddProduct(Product product)
    {
        int currentAmount;
        _products.TryGetValue(product.ProductId, out currentAmount);

        //if the product wasn't found, currentAmount will be 0
        _products[product.ProductId] = currentAmount + product.Amount;
    }
}

Comments:

• If you need an actual IEnumerable (as opposed to a dictionary), use a KeyedCollection
• Instead of creating your own class (which forces you to implement all the methods you want), you can write an extension method for IEnumerable<Product>, something like AddProduct - but that won't hide the regular Add method do I guess it's more of a quick and dirty way of doing it

Lastly, don't worry about the IBindingList part - you can always use a BindingSource