C# Declare variable in lambda expression

Question

I want to do a simple lambda expression like this:

IList list = GetSomeList();

MyEntity1 result = list.SingleOrDefault(         


        

Answer 1

If you want to use the "query comprehension" syntactic form you can do this:

var query = from entity1 in list
            let entity2 = GetMyEntity2(entity1)
            where entity2 != null
            where entity2.Id != null 
            where entity2.Id > 0
            select entity1;
var result = query.SingleOrDefault();

Note also that the middle "where" clause might not be necessary. If "entity2.Id" is a nullable int then it will be correctly checked for null by the lifted > operator.