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

Sure.

foreach(Activity activity in ActivityList.Where(a => a.Id == GuidToCompare) )
{        
    //Code here
}

But since Id implies there will be at most 1 activity:

//var act = ActivityList.Where(a => a.Id == GuidToCompare).SingleOrDefault(); // clearer
var act = ActivityList.SingleOrDefault(a => a.Id == GuidToCompare);          // shorter
if (act != null)
{
    //Code here
}

Answer 2

foreach(var activity in ActivityList.Where(p=>p.Id == GuidToCompare))
{

// Code here

}