Functions

Function is a code block that executes certain task.

Syntax

funcType funcName(args) { // Code to execute. }

Void Example

A void function doesn't return any value.

Example:

using System; namespace csharp { class Program { static void Main(string[] args) { // Calling a function: printHi(); } static void printHi() { Console.Write("Hi!"); } } }

Output:

Hi!

Returning Result

Via the return keyword a result can be returned.

Let's have an example in which rectangle's area is calculated by passing arguments about it's sides.

Example:

using System; namespace csharp { class Program { static void Main(string[] args) { double area = calcRectangleArea(3, 4); Console.Write(area); } static double calcRectangleArea(double widthArg, double heightArg) { return widthArg * heightArg; } } }

Output:

12

There are couple of things to mark:

• A functions is defined at lines 13 - 16. It accepts two arguments - widthArg and heightArg both of type double.
• The function calcRectangleArea returns a double result.
• calcRectangleArea is called at line 9.
• It's returned value is set in the variable area.

Common Exceptions

Return Mismatch

If a function returns value different than the specified type, it causes an exception.

static string returnName() { return 5; // Causes exception. }

In this case 5 should be replaced with string value.

Arguments Type Mismatch

namespace csharp { class Program { static void Main(string[] args) { functionName("John"); // causes exception } static int functionName(int arg) { return 5; } } }

Atline 12 the function expects argument of type int.

At line 9 an argument of string type is passed.

The passed argument at line 9 should be replaced with integer value.

Arguments Count Mismatch

namespace csharp { class Program { static void Main(string[] args) { calcTrapezoidArea(3, 4); // causes exception } static double calcTrapezoidArea(double a, double b, double h) { return (a + b) / 2 * h; } } }

The function calcTrapezoidArea expects 3 arguments but only 2 are passed to it.

Default Value

Default value may be specified for function parameters.

Let's look at the following:

using System; namespace csharp { class Program { static void Main(string[] args) { print(5); print(); } static void print(int arg = 3) { Console.WriteLine(arg); } } }

Output:

5 3

At line 10 the function argument is not passed thus it takes the default value - 3 specified at line 13.