using System;

class Program
{
    static void Main() => new Program().Foo();

    bool someCondition;
    void Foo()
    {
        DoSomething<string>("abc", someMethod);
        DoSomething<string[]>("abc", someMethod);
    }

    public void DoSomething<T>(string someString, Func<T, bool> someMethod)
    {
        if (someCondition)
        {
            string A = null;
            bool resultA = method(A);
        }
        else
        {
            string[] B = null;
            bool resultB = method(B);
        }
        // Some other stuff here ...
    }

    bool someMethod(string simpleString) => true;
    bool someMethod(string[] stringArray) => true;

    private bool method(string[] b)
    {
        throw new NotImplementedException();
    }

    private bool method(string a)
    {
        throw new NotImplementedException();
    }
}