Can I use an embedded lambda with the Contains method?

Question

I want to filter a list with FindAll

If I write:

.FindAll(
    p => p.Field == Value && 
    p.otherObjList.Contains(otherObj));

it's ok, but if I write

.FindAll(
    p => p.Field == Value && 
    p.otherObjList.Contains(
        q => q.Field1 == Value1 && 
        q.Field2 == Value2));

I get C# syntax error message: Unknown Method FindAll(?) of .. the otherObjList

I cannot define the otherObj exactly, because I know only the values of two fields, Field1 and Field2.

What have I done wrong? What can I do in this case?

Answer 1

The Contains() method for both most collection types as well as the LINQ version expects an argument of the same type as the collection, not a lambda.

It appears you are just trying to check if any item matches some condition. You should use the Any() method.

.FindAll(p => p.Field == Value
           && p.otherObjList.Any(q => q.Field1 == Value1 && q.Field2 == Value2))