Let's talk OOP Again

Let’s talk OOP again

You will encounter same problem, no matter what kind of software products you design or develop: how to design “User Object”? I usually design “User Object” like this ( The following is a simple example): I think most of us design “User Object” like this. En , looked as if there is no problems , Moreover ,it had became some people's habit We do like design “Add method” like “Add(xxx,xxx,xxx,xxx,xxx,xxx)” But, when I review some base OOP knowledge recently; I found there is something wrong. So, I change my old design(The following is sample example too):   If you can see I mind? Why “Example1” change to “Example2”? Two important changes at there: 1, I use “Property” replace “public variable”; public   virtual   string  UserName         ... {            get ...{ return _userName; }            set            ...{                if (_userName != value)                ...{                    if (value.Length > 16||value.Length<4)                    ...{                        throw new Exception("you can input 4-16 characters to UserID only");                    }                    if(...)                    ...{                        throw new Exception("... ...")                    }                    if(...)                    ...{                        throw new Exception("... ...")                    }                    _userName = value;                }            }        } 2, I use “Add (User xxx)” replace “Add (XXX,XXX,XXX)”; Do you know why? First, Use Property can get more control, the following code will show it: You can code like this: User objUser = new  User();Users objUser = new  Users();User.userName = TxtUserName.Text.Trim();User.Password = TxtPassword.Text;objUser.Add(objUser); Attention, if username is too long or short, “User Object” will throw a Exception, we can catch this exception. If you use old design,your code maybe like this: User objUser = new  User();String strUserName =  TxtUserName.Text.Trim();String strPassword = TxtPassword.Text;If(strUserName  > 16 ||  strUserName  < 4 ) ... {       … …} objUser.Add(strUserName,strPassword);   Which one more easy ?   Second, Like those method:”add”, “update” etc, use Object as parameter better than variable, It is more easy. You can see it from above code.   Third, it is most important thing: “Add”, "Update” methods not belong to “ User Object”, they should belong to “ Users Object” or belong to “ Dept Object”   I don’t know if you can understand the third. but you should try do it.   In this world, much thing we don’t know, but if when we try, we will get it