Functions

A function is a block of code that performs a specific task and can be called from other parts of the program. In C#, functions are also called methods.

Function structure

A function structure includes several key elements:

Return type - indicates the type of data the method returns. If the method returns nothing, the keyword void is used.
Method name - the identifier by which the method will be called.
Parameter list - in parentheses, the method's input parameters are listed (if any), each with a type and a name.
Method body - a block of code enclosed in curly braces {}, containing the method implementation.


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[return type] MethodName([parameters])
{
    // Method body
    // Execution logic
    // Return value (if the return type is not void)
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Function with no return value and no parameters

Used simply as a reusable block of code.


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void Hello()
{
    Console.WriteLine("Hello!");
}
Hello(); // function call
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Function with no return value and one parameter

For example, a function accepts a name parameter and inserts it into a greeting string


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void Hello(string name)
{
    Console.WriteLine($"Hello, {name}!");
}
Hello("John");
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Function with a return value and no parameters

For example, a function returns a greeting string


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string Hello()
{
    return "Hello!";
}
// declaring a variable and assigning it the function result
string helloString = Hello();
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Function with a return value and one parameter

For example, a function returns a greeting string in which name is inserted from the parameter


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string Hello(string name)
{
    return $"Hello, {name}!";
}
// you can use the function result immediately without declaring a variable
Console.WriteLine(Hello("John"));
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Function with a return value and multiple parameters

Functions can accept multiple parameters but return only one value (or nothing). For example, a function accepts 2 numbers as parameters and returns their sum


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int Add(int a, int b)
{
    int sum = a + b;
    return sum;
}
var result = Add(1, 2);
Console.WriteLine(result);
// or use the function result immediately without declaring a variable
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Exercises

Write a function with no return value and no parameters that always prints your birth year to the console.


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void MyYear()
{
    // Your code
}
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Write a function with no parameters that always returns your birth year.


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int MyYear()
{
    // Your code
}
int year = MyYear(); // function call
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Write a function that accepts a birth year, calculates age, and returns it. Call the function with your birth year and with another person's birth year.


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Write a function that accepts a name and birth year, calculates age, and returns a string in the format Name: {name}, age: {age}


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