How to restrict user for checking null for singelton instance in C#, .NET?

Question

I don't want that end programmer can user == or != operator against my singelton class.

End user can't do

if( SingleInstace == null)

I have overloaded != and == operator but it doesn't help.

I have a scenario in which I want to dispose of the singleton instance and initialize it with different parameter. For example my singelton instance is DBAccess and I want to intialize it with different server name. Therefore in between the calls of disposing of the singleton instance and intialize it with different server name ; there may be call of null check. In that case my singelton instance will be initialize with old server name.

Please help!!

Answer 1

SingleInstance should be private inside the Singleton class, so that nobody can access it outside of the class's "GetInstance" method.

Answer 2

It is pointless to prevent this. The client code can always cast it to object.

Answer 3

To implement your singleton, you'll use something like this:

class HasSingleton
{
    static public HasSingleton Instance {
        get 
        {
            if (_instance==null)
            {
                _instance=new HasSingleton();
            }
            return _instance;
        }
    static private _instance;
}

That way, you will never be able to get null for

HasSingleton.Instance

I omitted locking code for brevity.