How to modify a class having different methods..

Question

Hi....
I have a class having different methods with different parameters now I want to overload a method by increasing the one extra parameter like bellow..

public void Uper_PermonentMethod(string comm, long code, string itemname, string length, string collar, string neck, string chest, string waist, string cuff, string elbow, string hip, string ShoulderShape, string sleeves, string loosing, string armhole)
    {
    }
    public void Uper_PermonentMethod(string comm, long code, string itemname, string length, string collar, string neck, string chest, string waist, string cuff, string elbow, string hip, string ShoulderShape, string sleeves, string loosing, string armhole,string OrderType)
    {
    }

bold method is overloaded method with OrderType Field...

But when I perform event in my application that exception is happening that

Method Not Found...

please help me...