C# nullable check optimization

Question

Can anyone tell me how do I optimize below code.

if (report != null && 
    report.Breakdown != null &&
    report.Breakdown.ContainsKey(reportName.ToString()) &&
    report.Breakdown[reportName.ToString()].Result != null
    )

Which version of C# are you using? C# 6's null conditional operator can help here. — Jon Skeet, Apr 09 '17 at 07:32
Create an IsNull() operation on your Report type definition which does all the null checking for the report. Then you can just call it. — tom redfern, Apr 09 '17 at 07:36

Douglas · Accepted Answer · 2017-04-09T08:15:25.403

3

As others have mentioned, you can use the ?. operator to combine some of your null checks. However, if you're after optimizing for performance, you should avoid the double dictionary lookup (ContainsKey and index access), going for a TryGetValue instead:

MyType match = null;   // adjust type
if (report?.Breakdown?.TryGetValue(reportName.ToString(), out match) == true &&
    match?.Result != null)
{
    // ...
}

edited Apr 09 '17 at 08:15

answered Apr 09 '17 at 08:07

Douglas

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Don't do "== true" ;-) – Lucero Apr 09 '17 at 08:53
@Lucero: You need to in this case, since the result is `bool?`; otherwise, the compiler will give a syntax error. – Douglas Apr 09 '17 at 09:22
@Douglas You could use the null coalescing operator `??`, either are fine though. – TheLethalCoder Apr 09 '17 at 09:36

Ayman El Temsahi · Answer 2 · 2017-04-09T07:52:01.043

0

You can use null conditional operator but only on C# 6

if ( report?.Breakdown?.ContainsKey(reportName.ToString()) == true &&
     report.Breakdown[reportName.ToString()].Result != null )

edited Apr 09 '17 at 07:52

answered Apr 09 '17 at 07:34

Ayman El Temsahi

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Gives compile time error as: Operator && can not be applied to operands of type bool and bool? – Fahad Farooqi Apr 09 '17 at 07:45
sorry about that, it's fixed now – Ayman El Temsahi Apr 09 '17 at 07:54

score 0 · Answer 3 · answered Apr 09 '17 at 07:49

Ayman's answer is probably the best you can do for C# 6, for before that what you have there is pretty much the best you can do if all those objects are nullable.

The only way to optimize this further is to be checking if those objects are null before even calling the code, or better yet proofing your platform so this particular function shouldn't even be called in the first place if the values are null.

If you are just getting the value from from the dictionary however you can also simplify with the null coalescing operater '??'

Example:

MyDictionary['Key'] ?? "Default Value";

Thus if the Value at that entry is null you'll get the default instead.

So if this is just a fetch I'd just go

var foo = 
     report != null && 
     report.Breakdown != null &&
     report.Breakdown.ContainsKey(reportName.ToString()) ?
     report.Breakdown[reportName.ToString()].Result ?? "Default" :
     "Default";

But if you are actually doing things in the loop, then yeah you're pretty much at the best you can get there.

score 0 · Answer 4 · answered Apr 09 '17 at 07:51

0

For C# 6 and newer, you can do it this way:

if (report?.Breakdown?.ContainsKey(reportName.ToString()) == true &&
    report.Breakdown[reportName.ToString()].Result != null)

answered Apr 09 '17 at 07:51

Shadowed

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score 0 · Answer 5 · answered Apr 09 '17 at 08:03

Can you try below? Also probably better to ship it to a method.

// unless report name is already a string
string reportNameString = reportName.ToString();
if ( report?.Breakdown?.ContainsKey(reportNameString) &&
     report.Breakdown[reportNameString].Result != null )
{
    // rest of the code
}

C# nullable check optimization

5 Answers5