c# - Convert to Design Interface -

we have login structure replace structure. however, keep both incase new structure not work.

what have right now

passwordcontrol.cs

public class passwordcontrol {    public passwordcontrol()    {       // code here    }    public dologin()    {       // code here    } } 

main.cs

provide void btnlogin() {   passwordcontrol pw = new passwordcontrol();   pw.dologin(); } 

we convert design structure

iloginmanager.cs

interface iloginmanager  {   void dologin(); } 

so can add second structure

passwordcontrol2.cs

public class passwordcontrol2 {    public passwordcontrol()    {       // code here    }    public dologin()    {       // code here    } } 

how need modify code in main.cs take advantage of new design?

you want alternate between various implementations of same contract in runtime , that's why want use interface. interface contract: if class implements interface, provides services defined in interface. if class implements iloginmanager interface, class contains public dologin() method.

public interface iloginmanager  {     void dologin(); }  public class passwordcontrol : iloginmanager {    public passwordcontrol()    {       // code here    }    public void dologin()    {       // code here       debug.writeline("passwordcontrol.dologin()");    } }  public class passwordcontrol2 : iloginmanager {    public passwordcontrol2()    {       // code here    }    public void dologin()    {       // code here       debug.writeline("passwordcontrol2.dologin()");    } } 

you said want determine iloginmanager implementation when creating form. form can example read choice configuration file. means don't have recompile program when want change contract implementation, have change configuration file , restart program.

your form have following constructor:

public class myform {    iloginmanager _loginmanager;     public myform()    {       // let's assume read value 2       int choice = readchoicefromconfigfile();        if (choice == 1)       {          _loginmanager = new passwordcontrol();       }       else       {          _loginmanager = new passwordcontrol2();       }    } } 

so when press login button, proper implementation used:

private void btnlogin() {    // in our case passwordcontrol2.dologin() called _choice has been set 2    _loginmanager.dologin(); } 

even better if responsibility of creation proper loginmanager taken out of myform form should not know details - wants object implements iloginmanager should not care how it's made. ideally, you'll create iloginmanager implementer before creating form , you'd pass form's dependency (you "inject" it, via constructor example; read dependency injection). this:

public class myform {    iloginmanager _loginmanager;     public myform(iloginmanager loginmanager)    {       if (loginmanager == null)       {           throw new argumentnullexception("loginmanager");       }        _loginmanager = loginmanager;    } }   public static void main() {    iloginmanager loginmanager = createloginmanager();    application.run(new myform(loginmanager)); }  // factory method - creates desired instance implements given interface public static createloginmanager() {    iloginmanager loginmanager = null;     // let's assume read value 2    int choice = readchoicefromconfigfile();     if (choice == 1)    {        loginmanager = new passwordcontrol();    }    else    {        loginmanager = new passwordcontrol2();    }     return loginmanager; }