Question

I often find myself needing to compose a list of items from attributes of another list of items.
An approach I take is often similar to the following:

    public class MyClass
    {
        public Guid Identifier { get; set; }
        public byte[] Bytes { get; set; }
        public int ForeignKey { get; set; }

        public static List<MyClass> AllMyClass { get; }
    }

    private List<Guid> GetIdentifiers(int foreignKey)
    {
        List<Guid> identifiers = new List<Guid>();
        foreach (var item in MyClass.AllMyClass.FindAll(c => c.ForeignKey == foreignKey)
        {
            identifiers.Add(item.Identifier);
        }
        return identifiers;
    }

Now, is there any faster/simpler way of implementing this with a lamda expression? As in, I’d like to condense the operation into one line:

List<Guid> identifiers = MyClass.AllMyClass.MagicExpression(c => c.ForeignKey == foreignKey);

In addition, would such as expression be possible for the .NET 2.0 framework?

Answer 1

I think that something like that will work :

List<Guid> identifiers = MyClass.AllMyClass.Where(x => x.ForeignKey == foreignKey).Select(x => x.Identifier).ToList();

More over, they’re no lambda expressions in .Net 2.0.