Do we put something inside parentheses just because we want to able to call a method?

Question

When I call the Check method, I put "5" in parentheses. I do it because it requires an integer to call the method. Does this have anything to do with user input, or is it a necessary thing to be able to call method?

How can I not put something in parenthesis, but still be able to call the Check method?

static void Main(string[] args)
{
    Check(5);
    Console.Read();
}

public static void Check(int myInt)
{
    Console.WriteLine("Enter a number to checkc if it is odd or even number: ");
    string userInput = Console.ReadLine();
    int userInputNum;
    int parsedValue;

    if (Int32.TryParse(userInput, out userInputNum))
    {
        parsedValue = userInputNum;
    }
    else
    {
        parsedValue = 0;
        Console.WriteLine("You did not enter a number or anything.");
    }

    if ((parsedValue % 2) == 0)
    {
        Console.WriteLine("It is a even number.");
    }
    else
    {
        Console.WriteLine("It is an odd number.");
    }
}

Answer 1

The declaration of public static void Check(int myInt) method states it accepts a mandatory int parameter and calls it myInt.

Because of this, wherever you want to call the Check method, you have to provide a value for this parameter: Check(5), Check(100), Check(Random.Shared.NextInt()) and so on.

It is illegal to call the method without a value for its parameter, i.e. Check().

Now, the method Check accepts a mandatory parameter int myInt, but it doesn't actually use it anywhere. Since the parameter is useless, you may as well remove it from the method requirements.

public static void Check()
{
...

Once you remove the int myInt parameter from the method signature, you no longer have to provide a value for that parameter when you call the method. You call parameterless methods with simply Check() in your code.