How to check for null before I use in linq?

问题

I have an list of objects that contains another object in it.

List<MyClass> myClass = new List<MyClass>();

I want to do some linq like this

myClass.Where(x => x.MyOtherObject.Name = "Name").ToList();

Thing is sometimes "MyOtherObject" is null. How do I check for this?

回答1:

Simple, just add an AND clause to check if it's not null:

myClass.Where(x => x.MyOtherObject != null && x.MyOtherObject.Name = "Name").ToList();

回答2:

As of C# 6, you can also use a null conditional operator ?.:

myClass.Where(x => x.MyOtherObject?.Name == "Name").ToList();

This will essentially resolve the Name property to null if MyOtherObject is null, which will fail the comparison with "Name".

Try it online

回答3:

You can just make your predicate check for null...

myClass.Where(x => (x.MyOtherObject == null) ? false : x.MyOtherObject.Name == "Name").ToList();

回答4:

I would do something like this:

myClass.Where(x => x.MyOtherObject != null)
       .Where(y => y.MyOtherObject.Name = "Name")
       .ToList();

来源：https://stackoverflow.com/questions/5601397/how-to-check-for-null-before-i-use-in-linq