Sequence contains no elements?

From “Fixing LINQ Error: Sequence contains no elements”:

When you get the LINQ error “Sequence contains no elements”, this is usually because you are using the First() or Single() command rather than FirstOrDefault() and SingleOrDefault().

This can also be caused by the following commands:

• FirstAsync()
• SingleAsync()
• Last()
• LastAsync()
• Max()
• Min()
• Average()
• Aggregate()