c# - How do I recognize changes to an object using and EF6 Generated class in order to implement CanExecute? -

i binding button in xaml update user in database. want utilize canexecute enable button after change has been made property on viewmodel.

i using entity framework , wcf data service perform crud operations.

model class

    public virtual dbset<user> users { get; set; }      ...       namespace pk.data     {         using system;         using system.collections.generic;          public partial class user         {             public user()             {                 this.private_account = new hashset<private_account>();             }              public int id { get; set; }             public string username { get; set; }             public int superuser { get; set; }             public int enabled { get; set; }              public virtual icollection<private_account> private_account { get; set; }         }     } 

wcf service

public class pkservice {      // getusers() -      //  users database     [operationcontract]     public ienumerable<user> getusers()     {         using (var  context = new pkentities())         {             // needed in order handle ef objects hashes              context.configuration.proxycreationenabled = false;             // pull entity object fom db             var results = context.users.tolist();             // detatch entity model             results.foreach(e => context.entry(e).state = entitystate.detached);             //return detached object              return results;         }     }      // updateuser(user) -     //  update user in db     [operationcontract]     public void updateuser(user user){         using (var context = new pkentities())         {             context.configuration.proxycreationenabled = false;             context.entry(user).state = entitystate.modified;             context.savechanges();         }     } } 

view model #

 public class homeviewmodel: viewmodelbase     {         // homeviewmodel()         //  class constructor         public homeviewmodel()         {             this.refreshusers();             userlistclick = new relaycommand<selectionchangedeventargs>(_userlistclick);             saveuser = new relaycommand(saveuser);         }          // users          //  list of users in system         private ienumerable<user> _users;         public ienumerable<user> users         {             { return this._users; }             set             {                 this._users = value;                 this.raisepropertychanged("users");             }          }          // selected user         //  selected user         private user _selecteduser;         public user selecteduser         {             { return this._selecteduser; }             set             {                 if (this._selecteduser != value)                 {                     this._selecteduser = value;                     this.raisepropertychanged("selecteduser");                 }             }         }          // refreshusers()          //  method retrieving users db         private void refreshusers()         {             this._pkserviceclient.getuserscompleted += (s, e) =>                 {                     this.users = e.result;                 };             this._pkserviceclient.getusersasync();          }          // serverlistclick         public icommand userlistclick { get; private set; }         private void _userlistclick(selectionchangedeventargs e)         {             listview userlist = (listview)e.source;             _selecteduser = (user)userlist.selecteditem;             this.setuserdetailsvisible(visibility.visible);             this.raisepropertychanged("selecteduser");         }                  public icommand saveuser { get; private set; }         private void _saveuser()         {             this._pkserviceclient.updateuser(_selecteduser);         }     } } 

i believe possible tie relaycommand(saveuser, somecommand) , have somecommand return value can bind in xaml control enabled state of button.

i cannot seem find way using entity generated class handle this. assistance wonderful.

if understand correctly, want enable button connected saveuser command soon, there changes made selecteduser?

i believe possible tie relaycommand(saveuser, somecommand) , have somecommand return value can bind in xaml control enabled state of button.

this possible compositecommands (msdn documentation). here can call method "registercommand" , pass second command affects behavior of button connected compositecommand. if registered button returns canexecute == false, button disabled.

but add canexecute method relaycommand , check there, if entity has correct value. example, canexecute method check example username:

public homeviewmodel() {     this.refreshusers();     userlistclick = new relaycommand<selectionchangedeventargs>(_userlistclick);     saveuser = new relaycommand(saveuser, canexecutesaveuser); }  private bool canexecutesaveuser()     {         if (selecteduser.username == "foo")         {             return true;         }          return false;     } 

i not connect directly model. model should not bothered logic needed validation of ui. should add additional layer between viewmodel , wcf service, kind of userviewmodel can handle changes made properties of user directly. changes in these properties can trigger raisecanexecutechanged method of relaycommand.

i hope helps, if misunderstood you, please provide further explanation of problem.

edit:

after comment, think can implement inotifypropertychanged event , subscribe these events. this, necessary add additional layer of userviewmodel application. stripped example:

public homeviewmodel() {     this.refreshusers();     userlistclick = new relaycommand<selectionchangedeventargs>(_userlistclick);     saveuser = new relaycommand(saveuser, canexecutesaveuser);     selecteduserviewmodel.propertychanged += selecteduseronpropertychanged; }  private void selecteduseronpropertychanged(object sender, propertychangedeventargs propertychangedeventargs) {     if (propertychangedeventargs.propertyname.equals(nameof(userviewmodel.username)))     {         (saveuser relaycommand)?.raisecanexecutechanged();     } }