.Contains() on a list of custom class objects

I'm trying to use the .Contains() function on a list of custom objects

This is the list:

List<CartProduct> CartProducts = new List<CartProduct>();

And the CartProduct:

public class CartProduct
{
    public Int32 ID;
    public String Name;
    public Int32 Number;
    public Decimal CurrentPrice;
    /// <summary>
    /// 
    /// </summary>
    /// <param name="ID">The ID of the product</param>
    /// <param name="Name">The name of the product</param>
    /// <param name="Number">The total number of that product</param>
    /// <param name="CurrentPrice">The currentprice for the product (1 piece)</param>
    public CartProduct(Int32 ID, String Name, Int32 Number, Decimal CurrentPrice)
    {
        this.ID = ID;
        this.Name = Name;
        this.Number = Number;
        this.CurrentPrice = CurrentPrice;
    }
    public String ToString()
    {
        return Name;
    }
}

So i try to find a similar cartproduct within the list:

if (CartProducts.Contains(p))

But it ignores similar cartproducts and i don't seem to know what it checks on - the ID? or it all?

Thanks in advance! :)

If you are using .NET 3.5 or newer you can use LINQ extension methods to achieve a "contains" check with the Any extension method:

if(CartProducts.Any(prod => prod.ID == p.ID))

This will check for the existence of a product within CartProducts which has an ID matching the ID of p. You can put any boolean expression after the => to perform the check on.

This also has the benefit of working for LINQ-to-SQL queries as well as in-memory queries, where Contains doesn't.

You need to implement IEquatable or override Equals() and GetHashCode()

For example:

public class CartProduct : IEquatable<CartProduct>
{
    public Int32 ID;
    public String Name;
    public Int32 Number;
    public Decimal CurrentPrice;

    public CartProduct(Int32 ID, String Name, Int32 Number, Decimal CurrentPrice)
    {
        this.ID = ID;
        this.Name = Name;
        this.Number = Number;
        this.CurrentPrice = CurrentPrice;
    }

    public String ToString()
    {
        return Name;
    }

    public bool Equals( CartProduct other )
    {
        // Would still want to check for null etc. first.
        return this.ID == other.ID && 
               this.Name == other.Name && 
               this.Number == other.Number && 
               this.CurrentPrice == other.CurrentPrice;
    }
}

It checks to see whether the specific object is contained in the list.

You might be better using the Find method on the list.

Here's an example

List<CartProduct> lst = new List<CartProduct>();

CartProduct objBeer;
objBeer = lst.Find(x => (x.Name == "Beer"));

Hope that helps

You should also look at LinQ - overkill for this perhaps, but a useful tool nonetheless...

.Contains() on a list of custom class objects

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