Question

How to insert a default value to the returned collection if the where condition returns no results?

from i in data.collection
where i.Type == type
select i.Count

Answer 1

Use the Enumerable.DefaultIfEmpty method to do this.

Example (in method syntax because it IMHO is less awkward):

data.collection.Where(i => i.Type == type)
               .DefaultIfEmpty(defaultObject)
               .Select(i => i.Count);