What's the best implementation of safe navigation operator

Question

Is there an operator in C# that behaves like the safe navigation operator in groovy?

For instance, in groovy, doing something like this will prevent it from getting a NullPointerException if SessionData.CurrentSeminar is null.

int respId = SessionData.CurrentSeminar?.SeminCbaRespId;

How is this accomplished with C#?

You haven’t mentioned which value you want if CurrentSeminar is null. Do you want null or 0? — Roman Starkov, Apr 16 '12 at 13:10
It's worth noting that C# 6.0 added the safe navigation operator that works like in the questions example. — Ozraptor, Apr 16 '18 at 01:43

score 1 · Accepted Answer · answered Apr 16 '12 at 13:02

1

That operator does not exist in C#. You could do it with an inline-if

int respId = SessionData.CurrentSeminar != null ? 
   SessionData.CurrentSeminar.SeminCbaRespId : default(int);

or as an extension method.

var respId = SessionData.CurrentSeminar.GetSeminCbaRespId();

public static int GetSeminCbaRespId(this typeofCurrentSeminar CurrentSeminar)
{
   return CurrentSeminar != null ? CurrentSeminar.SeminCbaRespId : default(int);
}

answered Apr 16 '12 at 13:02

Daniel A. White

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This seems to be a good workaround, thanks. It's weired that such a perfect operator does not exist in C#. – kbaccouche Apr 16 '12 at 13:10
http://connect.microsoft.com/VisualStudio/feedback/details/192177/a-bit-more-c-syntactic-sugar-for-nulls – Daniel A. White Apr 16 '12 at 13:11
http://stackoverflow.com/a/2081709/33080 - it’s Eric’s standard answer. We want this, but we can’t implement everything due to time constraints. – Roman Starkov Apr 16 '12 at 13:12

score 0 · Answer 2 · answered Apr 16 '12 at 13:04

0

Maybe workaround like this?

int respId= ReferenceEquals(SessionData.CurrentSeminar,null)?-1:SessionData.CurrentSeminar.SeminCbaRespId;

answered Apr 16 '12 at 13:04

Rami Alshareef

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score 0 · Answer 3 · edited May 23 '17 at 10:08

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There is no operator for this, but you can get close. Try the one from this answer:

int respId = SessionData.CurrentSeminar.NullOr(s => s.SeminCbaRespId) ?? 0;

This gets extra useful if you need to chain several of them:

var elem = xml.Element("abc")
    .NullOr(x => x.Element("def"))
    .NullOr(x => x.Element("blah");

edited May 23 '17 at 10:08

Community

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answered Apr 16 '12 at 13:05

Roman Starkov

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score 0 · Answer 4 · edited Apr 16 '12 at 13:09

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The closest operator is ?:, but it's not as sugary.
So, you could do:

int respId = SessionData.CurrentSeminar != null ? SessionData.CurrentSeminar.SeminCbaRespId : 0; // if 0 is the "null" value

edited Apr 16 '12 at 13:09

Jeff LaFay

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answered Apr 16 '12 at 13:05

Steve Wong

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What's the best implementation of safe navigation operator

4 Answers4