What is the difference between static methods in a Non static class and static methods in a static class?

Question

I have two classes Class A and ClassB:

static class ClassA
{
    static string SomeMethod()
    {
        return "I am a Static Method";
    }
}

class ClassB
{
    static string SomeMethod()
    {
        return "I am a Static Method";
    }
}

I want to know what is the difference between ClassA.SomeMethod(); and ClassB.SomeMethod();

When they both can be accessed without creating an instance of the class, why do we need to create a static class instead of just using a non static class and declaring the methods as static?

Answer 1

The only difference is that static methods in a nonstatic class cannot be extension methods.

---

In other words, this is invalid:

class Test
{
    static void getCount(this ICollection<int> collection)
    { return collection.Count; }
}

whereas this is valid:

static class Test
{
    static void getCount(this ICollection<int> collection)
    { return collection.Count; }
}