Removing specific items in an Appointment List

Question

I have a list of calendar items that I have retrieved using EWS:

List<Appointment> apts = tApts.Items.ToList<Appointment>();

I am trying to remove all of the appointments in the list that have a subject that contains "Canceled" at the beginning of the title:

apts.RemoveAll(apt => apt.Subject.StartsWith("Canceled:"));

This is throwing me a "Object reference not set to an instance of an object."} System.Exception {System.NullReferenceException}.

I am assuming that this is happening because the Appointment subject is null.

However my solution to this is:

foreach (Appointment apt in apts)
{
    if (apt.Subject == null)
        continue;

    if (apt.Subject.StartsWith("Canceled:"))
        apts.Remove(apt);
}

However this also throws an error because I am changing the size of the List while I am iterating through it.

So what would be the best way to remove all the items in the last whose subject starts with "Canceled:", even though the subject may be null.

Answer 1

You could check if Subject property is null inside your lambda expression:

apts.RemoveAll(apt => apt.Subject != null && apt.Subject.StartsWith("Canceled:"));