"what is the difference between an interface and a class, and why i should use an interface when i can implement the methods directly in the class?" Code Answer

interfaces are excellent when you want to create something like it:

using system;

namespace myinterfaceexample
{
    public interface imyloginterface
    {
        //i want to have a specific method that i'll use in mylogclass
        void writelog();       
    }

    public class myclass : imyloginterface
    {

        public void writelog()
        {
            console.write("myclass was logged");
        }
    }

    public class myotherclass : imyloginterface
    {

        public void writelog()
        {
            console.write("myotherclass was logged");
            console.write("and i logged it different, than myclass");
        }
    }

    public class mylogclass
    {
        //i created a writelog method where i can pass as a parameter any object that implements imyloginterface.
        public static void writelog(imyloginterface mylogobject)
        {
            mylogobject.writelog(); //so i can use writelog here.
        }
    }

    public class mymainclass
    {
        public void dosomething()
        {
            myclass aclass = new myclass();
            myotherclass otherclass = new myotherclass();

            mylogclass.writelog(aclass);//myclass can log, and have his own implementation
            mylogclass.writelog(otherclass); //as myotherclass also have his own implementation on how to log.
        }
    }
}

in my example, i could be a developer who writes mylogclass, and the other developers, could create their classes, and when they wanted to log, they implement the interface imyloginterface. it is as they were asking me what they need to implement to use writelog() method in mylogclass. the answer they will find in the interface.