# ?: Operator (C# Reference)

The conditional operator (`?:`

), commonly known as the ternary 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;
```

## Remarks

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";
else
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.

## Example

```
class ConditionalOp
{
static double sinc(double x)
{
return x != 0.0 ? Math.Sin(x) / x : 1.0;
}
static void Main()
{
Console.WriteLine(sinc(0.2));
Console.WriteLine(sinc(0.1));
Console.WriteLine(sinc(0.0));
}
}
/*
Output:
0.993346653975306
0.998334166468282
1
*/
```