Creating a Utilities Class?

You will be better off using a static class with static methods. Then you won't need to instantiate your utilities class to use it. It will look something like this:

public static Utilites
{
  public static int sum(int number1, int number2)
  {
     test = number1+number2;
     return test;
  }
}

Then you can use it like this:

int result = Utilites.sum(1, 3);

If you are working with .NET 3.0 or above, you should look into extension methods. They allow you to write a static function that will act against a particular type, like Int32, while seeming to be a method on that object. So then you could have: int result = 1.Add(2);.

Try this out; it might just show you another way. ;)

C# Tutorial - Extension Methods

You should make it a static class, like this:

public static class Utilities {
    public static int Sum(int number1, int number2) {
        return number1 + number2;
    }
}

int three = Utilities.Sum(1, 2);

The class should (usually) not have any fields or properties. (Unless you want to share a single instance of some object across your code, in which case you can make a static read-only property.