Question

I have an interface list which stores a variety of objects derived from that interface. I would like to write a function where the caller specifies the type to extract. I’ve tried this:

List<IParts> PartList;

…

public List<IPart> Fetch(Type PartType)
{
   return this.PartList.OfType<PartType>().Cast<IPart>().ToList();
}

But it doesn’t like a passed type. Any suggestions?

Answer 1

If you have to support various types at runtime (rather than at compile time with generics):

public List<IPart> Fetch(Type PartType)
{
    if (!typeof(IPart).IsAssignableFrom(PartType))
    {
        throw new ArgumentOutOfRangeException("PartType", "Must derive from IPart");
    }
    return this.PartList.Where(i => i != null && PartType.IsAssignableFrom(i.GetType())).ToList();
}