Question

I have a static class Manager it should adapt between two tiers of logic would it be a bad practice
to devide functionalitlies by nesting static classes inside it?
I have about two dozen diffrent subjects to manage with 2 -3 functions each.
and would like to avoid creating 2 dozen classes for this

I mean use this:

static class Manager
{
    static class Type1
    {
        static void Method1();
        static void Method2();
        static void Method3(); 
    }
    static class Type2
    {
        static void Method4();
        static void Method5();
        static void Method6(); 
    }
    static class Type3
    {
        static void Method7();
        static void Method8();
        static void Method9();
    }
}

instead of:

static class Manager
{
        static void Method1();
        static void Method2();
        static void Method3(); 
        static void Method4();
        static void Method5();
        static void Method6(); 
        static void Method7();
        static void Method8();
        static void Method9();
}

something like namespaces, but inside a class.

Answer 1

There are a number of options, if you are about design choices.

First, you can pour everything into a single class which would be terribly hard to debug and mixed several responsibilities.

Second, you can create nested classes, as you also noted, where you have better seperation of concerns / code but still have everything hardcoded and in one big source-code file.

Third, which is much more extendable, you can consider any container pattern you wish. I have listed one below which keeps your classes seperate and more easily testable should you care, as well as swappable.

interface IManagementRole 
{
}

class Dummy1: IManagementRole
{
    public void Method1() { Console.WriteLine("Dummy1.Method1()"); }
    public void Method2() { Console.WriteLine("Dummy1.Method2()"); }
}

class Dummy2: IManagementRole
{
    public void Method3() { Console.WriteLine("Dummy2.Method3()"); }
    public void Method4() { Console.WriteLine("Dummy2.Method4()"); }
}

static class Manager
{
    private static Dictionary<Type, IManagementRole> myTypes = new Dictionary<Type, IManagementRole>();

    static Manager()
    {
        myTypes.Add(typeof(Dummy1), new Dummy1());
        myTypes.Add(typeof(Dummy2), new Dummy2());
    }

    public static T GetManagableType<T>() where T: class
    {
        if (myTypes.ContainsKey(typeof(T)))
        {
            return myTypes[typeof(T)] as T;
        }

        throw new ArgumentException("Type is not a managable type.", "T");
    }
}

class Program
{
    public static void Main(string[] args)
    {
        Manager.GetManagableType<Dummy1>().Method1();
        Manager.GetManagableType<Dummy1>().Method2();
        Manager.GetManagableType<Dummy2>().Method3();

        Console.Write("Press any key to continue . . . ");
        Console.ReadKey(true);
    }
}