CODEWITHSUNDEEP
c#.netvisual-studiounreachable-code
Subin Jacob
Subin Jacob

Reputation: 4864

How this if condition is unreachable?

IsSaveNew is type of bool? CoverLetterId is type of int?

if (coverLetter.IsSaveNew ?? true || coverLetter.CoverLetterId == null)

coverLetter.CoverLetterId == null. This statement is marked as unreachable in visual studio(2012).

But if IsSaveNew was false, then it would reach at the second condition. Why Visual Studio says so?

Upvotes: 1

Views: 127

Answers (4)

Soner Gönül
Soner Gönül

Reputation: 98740

|| has highger precedence than ?? operator.

Check out 7.2.1 Operator precedence and associativity

Your true || coverLetter.CoverLetterId == null works first. If you want coverLetter.IsSaveNew ?? true should work first, just use parentheses around it.

Like;

if ((coverLetter.IsSaveNew ?? true) || coverLetter.CoverLetterId == null)

But still visual studio says its unreachable

That means (probably) your coverLetter.IsSaveNew ?? true returns true, that's why your second operand doesn't evaluate.

From || Operator (C# Reference)

If the first operand evaluates to true, the second operand isn't evaluated. If the first operand evaluates to false, the second operator determines whether the OR expression as a whole evaluates to true or false.

Upvotes: 3

Ramashankar
Ramashankar

Reputation: 1658

You can put coverLetter.IsSaveNew ?? true in paranthesis to solve this. like-

if ((coverLetter.IsSaveNew ?? true) || coverLetter.CoverLetterId == null)

Upvotes: 1

Patrick Hofman
Patrick Hofman

Reputation: 156918

You'd better use GetValueOrDefault as the ?? part will always evaluate to true

Upvotes: 0

Frédéric Hamidi
Frédéric Hamidi

Reputation: 262919

Looks like an operator precedence issue. Your statement is evaluated as:

if (coverLetter.IsSaveNew ?? (true || coverLetter.CoverLetterId == null))

So the right-hand operand to the || operator will never be evaluated since its left-hand operand is the literal true.

You can add parentheses to solve this problem:

if ((coverLetter.IsSaveNew ?? true) || coverLetter.CoverLetterId == null)

Upvotes: 6

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