IDE0029 Null check can be simplified C# 6.0 ASP.NET

Question

In my visual studio 2017, there is a message in Error List windows like this.

IDE0029 Null check can be simplified

I google it and found this link Null-conditional operators ?. and ?[] but i don't understand.

My code is simple like this:

string varIP = Request.UserHostAddress != null ? Request.UserHostAddress : "IP null";

How to simplify it again?

Answer 1

string varIP = Request.UserHostAddress != null ? Request.UserHostAddress : "IP null";

Can be re-written with the null-coalescing operator:

string varIP = Request.UserHostAddress ?? "IP null";

This will use the value of UserHostAddress, unless it is null in which case the value to the right ("IP null") is used instead.

If there is any possibility of Request being null, you can additionally used the null-conditional operator that you mentioned in the question:

string varIP = Request?.UserHostAddress ?? "IP null";

In this case if the Request is null then the left hand side will evaluate as null, without having to check UserHostAddress (which would otherwise throw a NullReferenceException), and the value to the right of the null-coalescing operator will again be used.