how to make something so that all functions can use it csharp code example

Example 1: c# funtion

public int AddNumbers(int number1, int number2){    int result = number1 + number2;    if(result > 10)    {    return result;    }    return 0;}

Example 2: functions c#

public void SayHello(string name) 
{
    Console.WriteLine("Hello");
}

public void SayName()
{
	Console.WriteLine("What is your name?");
	string name = Console.ReadLine(); 
	SayHello(name);
}