Книга: C# 2008 Programmer

if-else Statement

if-else Statement

The most common flow-control statement is the if-else statement. It evaluates a Boolean expression and uses the result to determine the block of code to execute. Here's an example:

int num = 9;
if (num % 2 == 0) Console.WriteLine("{0} is even", num);
else Console.WriteLine("{0} is odd", num);

In this example, if num modulus 2 equals to 0, the statement "9 is even" is printed; otherwise (else), "9 is odd" is printed.

Remember to wrap the Boolean expression in a pair of parentheses when using the if statement.

If you have multiple statements to execute after an if-else expression, enclose them in {}, like this:

int num = 9;
if (num % 2 == 0) {
 Console.WriteLine("{0} is even", num);
 Console.WriteLine("Print something here...");
else {
 Console.WriteLine("{0} is odd", num);
 Console.WriteLine("Print something here...");

Here's another example of an if-else statement:

int num = 9;
string str = string.Empty;
if (num % 2 == 0) str = "even";
else str = "odd";

You can rewrite these statements using the conditional operator (?:), like this:

str = (num % 2 == 0) ? "even" : "odd";
Console.WriteLine(str); //---odd---

?: is also known as the ternary operator.

The conditional operator has the following format:

condition ? first_expression : second_expression;

If condition is true, the first expression is evaluated and becomes the result; if false, the second expression is evaluated and becomes the result.

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