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The outcome of the || operator is true if either of the Boolean expressions it evaluates is true. You
use the || operator to determine whether any one of a combination of Boolean expressions is true. For
example, the following statement assigns the value true to invalidPercentage if the value of percent is
less than 0 or the value of percent is greater than 100:
bool invalidPercentage;
invalidPercentage = (percent < 0) || (percent > 100);
Short circuiting
The && and || operators both exhibit a feature called short circuiting. Sometimes, it is not necessary to
evaluate both operands when ascertaining the result of a conditional logical expression. For example,
if the left operand of the && operator evaluates to false, the result of the entire expression must be
false, regardless of the value of the right operand. Similarly, if the value of the left operand of the ||
operator evaluates to true, the result of the entire expression must be true, irrespective of the value of
the right operand. In these cases, the && and || operators bypass the evaluation of the right operand.
Here are some examples:
(percent >= 0) && (percent 100)
In this expression, if the value of percent is less than 0, the Boolean expression on the left side of
|| evaluates to true. This value means that the result of the entire expression must be true, and the
Boolean expression to the right of the || operator is not evaluated.
If you carefully design expressions that use the conditional logical operators, you can boost the
performance of your code by avoiding unnecessary work. Place simple Boolean expressions that can
be evaluated easily on the left side of a conditional logical operator, and put more complex expressions
on the right side. In many cases, you will find that the program does not need to evaluate the
more complex expressions.
Summarizing operator precedence and associativity
The following table summarizes the precedence and associativity of all the operators you have
learned about so far. Operators in the same category have the same precedence. The operators in
categories higher up in the table take precedence over operators in categories lower down.
Category Operators Description Associativity
Primary ()
++
--
Precedence override
Post-increment
Post-decrement
Left
90 PART I Introducing Microsoft Visual C# and Microsoft Visual Studio 2015