how to call static method inside non static method through instance

Question

I understand that we could use the class name.method but I was wondering if there was a way to do it through an instance. Can you provide me an example also. The reason I'm asking is because my professor said:

You MUST invoke the extension method using calls that use the static call form and the instance call form

Answer 1

With the edit that this is talking about extension methods, then it becomes easier!

With the same example as below:

bool hasValue1 = s.HasValue(); // use the instance syntax
bool hasValue2 = StringExtensions.HasValue(s); // use the static syntax

Note that these are 100% identical; once compiled to IL you cannot determine which form was used.

---

Short answer: "no", per CS0176:

CS0176 Member '{name}' cannot be accessed with an instance reference; qualify it with a type name instead

Slightly longer answer: if you really want to do that, maybe extension methods are what you are looking for; for example:

static class StringExtensions
{
    public static bool HasValue(this string value)
    {
        return !string.IsNullOrEmpty(value);
    }
}
class Program
{
    static void Main()
    {
        string s = /* some string or null reference */
        bool hasValue = s.HasValue();
    }
}