Export (0) Print
Expand All

?: Operator (C# Reference)

The conditional operator (?:) returns one of two values depending on the value of a Boolean expression. Following is the syntax for the conditional operator.

condition ? first_expression : second_expression;

The condition must evaluate to true or false. If condition is true, first_expression is evaluated and becomes the result. If condition is false, second_expression is evaluated and becomes the result. Only one of the two expressions is evaluated.

Either the type of first_expression and second_expression must be the same, or an implicit conversion must exist from one type to the other.

You can express calculations that might otherwise require an if-else construction more concisely by using the conditional operator. For example, the following code uses first an if statement and then a conditional operator to classify an integer as positive or negative.

int input = Convert.ToInt32(Console.ReadLine());
string classify;

// if-else construction.
if (input > 0)
    classify = "positive";
    classify = "negative";

// ?: conditional operator.
classify = (input > 0) ? "positive" : "negative";

The conditional operator is right-associative. The expression a ? b : c ? d : e is evaluated as a ? b : (c ? d : e), not as (a ? b : c) ? d : e.

The conditional operator cannot be overloaded.

class ConditionalOp
    static double sinc(double x)
        return x != 0.0 ? Math.Sin(x) / x : 1.0;

    static void Main()
Was this page helpful?
(1500 characters remaining)
Thank you for your feedback
© 2014 Microsoft