What's the Difference Between the `||` and `|` Operators in Programming?

Using OR Operators in Programming: | vs ||

When working with OR expressions in programming languages like C# and PHP, it's common to use the double pipe (||) operator. However, occasionally, the single pipe (|) is also used. What's the difference between these two operators?

Short-Circuiting Behavior

The double pipe (||) is a "short-circuit" operator. This means that in an OR expression involving multiple conditions, if the first condition evaluates to true, the remaining conditions will not be evaluated.

For example:

if (condition1 || condition2 || condition3)

If condition1 is true, the evaluation stops, and condition2 and condition3 are not checked.

Regular Evaluation

In contrast, the single pipe (|) operator performs regular evaluation. This means that it will always evaluate all the conditions in an OR expression, regardless of the result of the first condition.

if (condition1 | condition2 | condition3)

In this example, all three conditions will be evaluated, even if condition1 is true.

Potential Caveats

While the single pipe (|) operator generally provides better performance, it has one potential caveat. Unlike the short-circuit OR, the regular OR operator does not stop evaluating when it encounters a null reference or similar error.

For example:

if (class != null || class.someVar < 20)

If class is null, the regular OR operator will still try to evaluate class.someVar, resulting in a NullReferenceException.

Bitwise Operations

In addition to their use in OR expressions, the | and & operators can also be used for bitwise operations. In this context, they perform binary operations on the binary representations of their operands.

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