Convert the following program to use methods

Always keep common methods or Business Logic method's loosely coupled with UI , this means while creating method don't use any keywords that are specific to a particular UI, for example Console.ReadLine() or WritleLine() methods are specific to Console Apps so if you will use those methods inside your user defined (custom) methods then you won't be able to use them or call them from windows app, mobile app or MVC web app or web forms.

so,

first create a class library project inside your solution and inside that create a class , name it as common and create methods as

public class Common
{
public bool IsEven(int n)
{
return  n%2==0; // any integer which is not even will always be odd so no need to create odd method
}

}

use it inside your console apps as

using System;

public class Program
{
   static void Main(string[] args)
{
    Common c= new Common();
int i=0;
   while(i<3)
{
     Console.WriteLine("Enter a value ");
   int value = int.Parse(Console.ReadLine());
    if (c.IsEven(value))
    {
        Console.WriteLine($"{value} is even");
    }
    else
    {
        Console.WriteLine($"{value} is odd");
    }
i++;
}
}


}

you can also create method within UI program class as

using System;

public class Program
{
   static void Main(string[] args)
{
    Common c= new Common();
int i=0;
   while(i<3)
{
     Console.WriteLine("Enter a value ");
   int value = int.Parse(Console.ReadLine());
    if (c.IsEven(value))
    {
        Console.WriteLine($"{value} is even");
    }
    else
    {
        Console.WriteLine($"{value} is odd");
    }
i++;
}
}

public class Common
{
public bool IsEven(int n)
{
return  n%2==0; // any integer which is not even will always be odd so no need to create odd method
}

}
}