static void DeclareAndPrintVars(int x)
{
  int y = 3;
  // Using x and y inside the method is fine.
  Console.WriteLine(x + y);
}

static void Main()
{
  DeclareAndPrintVars(5);

  // x and y only exist inside the body of DeclareAndPrintVars, so we cannot use them here.
  Console.WriteLine(x * y);
}