Replicating C Pointer in C#

pointer.cs

// 1) 'ref'

// ref keyword means "pass by reference" - edits
// made in this function affect the actual variable
int someNum = 5;
AddOne(ref someNum);
// someNum now = 6

void AddOne(ref int i)
{
    i++;
}

// 2) 'return'
// As stated you could return the value instead
int someNum = 5;

// Call AddOne, passing in our someNum value and set the value
// that AddOne returns back into out someNum variable.
someNum    = AddOne(someNum);

int AddOne(int i)
{
    // You could return right away by doing something like
    // return ++i;
    // however for verbosity, im not in this example.
    i += 1;
    return i;
}

// 3) 'Extension method'
int someNum    = 5;

// I cant think of how to correctly say what an extension method
// actually is so heres a link:
// https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/extension-methods
// https://www.dotnetperls.com/extension
someNum.AddOne();

public static int AddOne(this int i)
{
    i += 1;
    return i;
}