c# - Changing the model -

imagine simple usercontrol 1 textbox (customername), , 2 buttons (save/cancel).

this usercontrol sits within parent control 2 more buttons (previouscustomer/nextcustomer)

the problem don't know pass in model presenter. go through view constructor? if model changes (previouscustomer/nextcustomer clicked)? create new view every time? seems wasteful if usercontrol complex many children. implement updatemodel method in view , presenter, or incorrect?

here's code:

public interface imodel {     string customername { get; set; } }  public class presenter {     private iview _view;     private imodel _model;      public presenter(iview view, imodel model)     {         _view = view;         _model = model;         _view.customername = _model.customername;     }      public void save()     {         _model.customername = _view.customername;     }      public void cancel()     {         _view.customername = _model.customername;     }      public void updatemodel(imodel newmodel)     {         _model = newmodel;         _view.customername = _model.customername;     } }  public interface iview {     string customername { get; set; } }  public class view : usercontrol, iview {     private presenter _presenter;      public string customername     {         { return customernameeditbox.text; }         set { customernameeditbox.text = value; }     }      //is right place pass in model?     public view(imodel model)     {         _presenter = new presenter(this, model);     }      private void savebutton_click(object sender, eventargs e)     {         _presenter.save();     }      private void cancelbutton_click(object sender, eventargs e)     {         _presenter.cancel();     }      public void updatemodel(imodel newmodel)     {         _presenter.updatemodel(newmodel);     } } 

edit: stated in comments below, think best have view dumb , know nothing of presenter or model. here revised code.

model:

public interface imodel {     string customername { get; set; } }  public class model : imodel {     public string customername { get; set; }      public model(string name)     {         customername = name;     } } 

view:

public interface iview {     event eventhandler saveclick;     event eventhandler cancelclick;     string customername { get; set; } }  public class view : usercontrol, iview {     public event eventhandler saveclick     {         add { savebutton.click += value; }         remove { savebutton.click -= value; }     }      public event eventhandler cancelclick     {         add { cancelbutton.click += value; }         remove { cancelbutton.click -= value; }     }      public string customername     {         { return customernameeditbox.text; }         set { customernameeditbox.text = value; }     } } 

presenter:

public class presenter {     private iview _view;     private imodel _model;      public control view     {         { return (control)_view; }      }      public presenter(iview view, imodel model)     {         _view = view;         _view.saveclick += new eventhandler(_view_saveclick);         _view.cancelclick += new eventhandler(_view_cancelclick);         _model = model;         _view.customername = _model.customername;     }      void _view_saveclick(object sender, eventargs e)     {         _model.customername = _view.customername;     }      void _view_cancelclick(object sender, eventargs e)     {         _view.customername = _model.customername;     }      public void changemodel(imodel newmodel)     {         _model = newmodel;         _view.customername = _model.customername;     } } 

usage:

public class mainprogram : form {     public void arbitrarymethod()     {         //create new model object         imodel model1 = new model("test1");          //create presenter model , view implementing iview         presenter presenter = new presenter(new view(), model1);          //add view panel control in form         mainpanel.controls.add(presenter.view);          //change model         imodel model2 = new model("test2");         presenter.changemodel(model2);     } } 

if design mvp (model view presenter) should create model inside presenter. that's idea behind pattern. view communicates presenter , presenter offers him methods, properties, events needed. in example decided create model well. can that, please hide view. related example, remove imodel parameter in constructor , create new 1 in code instead.

consider setting view changes via methods (_view.setname("me"). make life easier later.

there's no need create new winforms form. perhaps, don't understand point here..

update:

take @ example below. have interfaces view, presenter , model ( based code). renamed imodel icustomer make point clear. presenter creates model doing i/o stuff , gets view interface updating windows or whatever behind interface.

public interface iview {     public string customername { get; set; } }  public interface icustomer {     string customername { get; set; } }  public interface imodel {     void save(icustomer entity);     void update(icustomer entity);     icustomer create(); }   public class customer : icustomer {     public string customername {get;set;}  }  public class mymodel : imodel {      public void save(icustomer entity)     {         //do here..     }      public void update(icustomer entity)     {         //do here..     }      public icustomer create()     {         return new customer();     } }  public class presenter {     private iview _view;     private icustomer _entity;     private imodel _model = new mymodel();      public presenter(iview view)     {         _view = view;         _model = new mymodel();         _entity = _model.create();          _view.customername = _entity.customername;     }      public void save()     {         _model.save(_entity);     }      public void cancel()     {         _entity = _model.create();     }      public void updatemodel(icustomer customer)     {         _model.update(customer);         _view.customername = customer.customername;     } }