Using .Contains() on a property in a list

Question

I have a List of Activity. In the Activity class is an ID property (a Guid for arguments sake). I want to check if this list has an Activity in it with a Guid I have. Rather

Answer 1

For those who can't use LINQ:

List ActivityList = new List();

foreach (Activity activity in ActivityList.FindAll(delegate(Activity a)
    {
        return a.Id == GuidToCompare;
    }))
{
    //Code here
}