Avoiding Null-object reference Entity framework

Question

I have a question about using Entity Framework.

I want to access a property of a model connected with another model. But if "parent" object is Null, the ?? operator does not help.

For example: My Customer model has Company model inside. I want to access Customer.Company.Name property. Where the Customer object is allready null, I get the null object reff error.

Sample of accessing the property on null object

If the object is null I would like it to return "". One solution is to write a loner code like:

(Customer!=null) ? ((Customer.Company!=null) ? Customer.Company.Name ?? "" : "" ) : ""

I know this is not the clean way, but there would be nice if there is a solution like ?? which detects null in parent object, too.

Your answer for a clean solution is null operator (informit.com/articles/article.aspx?p=2421572). Unfortunately it is available since C# version 6. Otherwise, you have no alternative than what you have already written, that means check every parent explicitly if it is null — jambonick
– jambonick, Commented Mar 8, 2017 at 8:00
@jambonick Well, you do have some alternatives. You could write some helper methods that act a bit like '?.', say. — Rawling
– Rawling, Commented Mar 8, 2017 at 8:08

Tamás Szabó · Accepted Answer · 2017-03-08 07:59:45Z

2

As Lei Yang mentioned in the comments you can write something like

var name = Customer?.Company?.Name;

(If you are using C# 6)

answered Mar 8, 2017 at 7:59

Tamás Szabó

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5 Comments

gtu Over a year ago

This actually opened a whole new chapter in my programming life :) Thank you for this. This kind of propagates null to the last check. Also my first example is kind of dumb, because Name which is of type 'string' is never null if the object exists. So the Name??"" is useless. Firstly I didn't know which version am I using. I read somewhere that C#6 came with .NET4.6 and in my project I am using 4.5.2 and I wasn't sure if it would work. But it does. :) Thank you all very much,

Ivan Stoev Over a year ago

A bit off topic, but since C# 7 is coming today, do we still need to say "if you are on C# 6" - I never saw specifically mentioning C# 5, 4, etc.

Tamás Szabó Over a year ago

I just added that make sure... For example at work some of our older projects are still using .NET4.5.

Ivan Stoev Over a year ago

It comes with VS, not .NET version. C#6 => VS2015, C#7 => VS2017 etc. Anyway.

Tamás Szabó Over a year ago

You're right, I'm sorry. I don't know why I thought it depended on the framework. It's also using VS2013 so that might have confused me.

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