C# 'or' operator?

Question

Is there an or operator in C#?

I want to do:

if (ActionsLogWriter.Close or ErrorDumpWriter.Close == true)
{
    // Do stuff here
}

But I'm not sure how I could do something like that.

@lndebi: Your questions reveal a strikingly uneven grasp of C#. Consider walking through some tutorials to balance yourself out before tacking package managers and whatever else you're working on. msdn.microsoft.com/en-us/library/… is a place to start. — Michael Petrotta, Nov 17 '09 at 03:01
Not to mention you've got a weird if statement to begin with. Why are you only explicit about the 2nd condition being true, and implicit with the first? — mpen, Nov 17 '09 at 03:11
Yeah, i'm kinda self-taught with this stuff and eventually I will take a class, but I like learning as I go more than learning all at once using a book or written text because I can't ask a piece of paper why something isn't working or why it works that way. That is way I'm asking a lot of questions of StackOverflow — Jarred Sumner, Nov 17 '09 at 05:29
I'm self taught also. I can use the or operator all day in Python. Now I'm reading some C# code and seeing this || everywhere and I don't know what to ask. Thanks to he who asked the question and BIG thanks to those that just give an answer and move on. — Justin, Feb 24 '12 at 20:58
@Justin remember that python uses | for bitwise or, so it's not very different... — fabspro, Apr 24 '13 at 14:21
I think it's healthy for stackoverflow to contain answers to questions across the entire spectrum from easy to complex. One stop shops are very powerful. There is a reason why WalMart and Amazon sell everything from bread to vacuum cleaners. — Jeff, Oct 18 '22 at 19:25

Jeff Sternal · Accepted Answer · 2011-01-06T20:49:18.763

96

C# supports two boolean or operators: the single bar | and the double-bar ||.

The difference is that | always checks both the left and right conditions, while || only checks the right-side condition if it's necessary (if the left side evaluates to false).

This is significant when the condition on the right-side involves processing or results in side effects. (For example, if your ErrorDumpWriter.Close method took a while to complete or changed something's state.)

edited Jan 06 '11 at 20:49

answered Nov 17 '09 at 03:00

Jeff Sternal

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Should that read: || only checks the right-side condition if the left side evaluates to false? Since TRUE OR ANYTHING is always TRUE? – ParmesanCodice Nov 17 '09 at 08:21
Just a minor thing - there are ofcourse more boolean operators than that, maybe rephrase to "two boolean/logic OR operators". – sharkin Nov 17 '09 at 11:39
4

Be careful: || is a logical operator and | is a binary operator – Matthieu Nov 17 '09 at 11:42
10

@Matthieu: No, if the operands are boolean, the |-operator is a logical operator. It's only treated as binary if operands are integral. – sharkin Nov 17 '09 at 11:47
There is also the `or` keyword now too... – justin.m.chase Dec 01 '22 at 15:47

score 14 · Answer 2 · answered Mar 15 '21 at 20:32

As of C# 9, there is an or keyword that can be used in matching a "disjunctive pattern". This is part of several new pattern matching enhancements in this version.

An example from the docs:

public static bool IsLetter(this char c) => c is >= 'a' and <= 'z' or >= 'A' and <= 'Z';

score 9 · Answer 3 · answered Nov 17 '09 at 03:03

9

Also worth mentioning, in C# the OR operator is short-circuiting. In your example, Close seems to be a property, but if it were a method, it's worth noting that:

if (ActionsLogWriter.Close() || ErrorDumpWriter.Close())

is fundamentally different from

if (ErrorDumpWriter.Close() || ActionsLogWriter.Close())

In C#, if the first expression returns true, the second expression will not be evaluated at all. Just be aware of this. It actually works to your advantage most of the time.

answered Nov 17 '09 at 03:03

Josh

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Does it matter if it's a property or method? In this context I would guess the property-code is called just as well as for methods. – sharkin Nov 17 '09 at 11:50
That is a good point. If the properties had side effects (which is also very bad design) the same caveat applies. – Josh Nov 17 '09 at 19:36

score 4 · Answer 4 · answered Nov 17 '09 at 02:57

4

if (ActionsLogWriter.Close || ErrorDumpWriter.Close == true)
{    // Do stuff here
}

answered Nov 17 '09 at 02:57

Dave Barker

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score 3 · Answer 5 · answered Jan 18 '14 at 04:47

The single " | " operator will evaluate both sides of the expression.

    if (ActionsLogWriter.Close | ErrorDumpWriter.Close == true)
{
    // Do stuff here
}

The double operator " || " will only evaluate the left side if the expression returns true.

    if (ActionsLogWriter.Close || ErrorDumpWriter.Close == true)
{
    // Do stuff here
}

C# has many similarities to C++ but their still are differences between the two languages ;)

score 2 · Answer 6 · answered Nov 17 '09 at 02:58

2

just like in C and C++, the boolean or operator is ||

if (ActionsLogWriter.Close || ErrorDumpWriter.Close == true)
{
    // Do stuff here
}

answered Nov 17 '09 at 02:58

Jeff Paquette

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score 2 · Answer 7 · answered Nov 17 '09 at 02:58

2

Or is || in C#.

You may have a look at this.

answered Nov 17 '09 at 02:58

Secko

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C# 'or' operator?

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