Why is this error, 'Sequence contains no elements', happening?

Question

I am getting an Invalid Operation Exception, the stack is down below. I think it is because db.Responses.Where(y => y.ResponseId.Equals(item.ResponseId)).First();

Answer 1

In the following line.

temp.Response = db.Responses.Where(y => y.ResponseId.Equals(item.ResponseId)).First();

You are calling First but the collection returned from db.Responses.Where is empty.