Question

here’s my code. it works

var someField = "abc";

var list = Entities.Where(x=>SomeField).FirstOrDefault();

here’s the problem, someField can also be null or string.empty. If someField is null or string.empty, I will select everything where SomeField is null or string.empty.

var list = Entities.Where(x=>SomeField  == null || SomeField == string.empty).FirstOrDefault();

right now, I have an if else statement to check if someField has value,then decided which query to use.

I need to combine the 2 queries into one. because if there are fields we need to check, then this if else statemetn will get very long.

Answer 1

I suspect you actually want to match x.SomeField == someField, or everything if someField is null or empty, right?

I would do this:

var fetchAll = string.IsNullOrEmpty(someField);
var list = Entities.FirstOrDefault(x => fetchAll || x.SomeField == someField);

You can inline it, but I think the above is clearer than checking whether someField is null or empty within the query.

Note that I’ve used the overload of FirstOrDefault which takes a predicate – this is equivalent to using Where followed by FirstOrDefault, but a bit more concise.