c# - CanExecute in DelegateCommand and expression declaration doesn't work -


my question straightforward. why works:

public delegatecommand logincommand { get; }  func<bool> canexecutelogin = () => !stringservice.isnullorempty(_entries.logintext, _entries.passwordtext); logincommand = new delegatecommand(onlogintapped, canexecutelogin);

but doesn't:

public delegatecommand logincommand => new delegatecommand(onlogintapped,             () => !stringservice.isnullorempty(_entries.logintext, _entries.passwordtext));

i check so:

 public string loginentrytext         {             { return _entries.logintext; }             set             {                 _entries.logintext = value;                 logincommand?.raisecanexecutechanged();             }         }

doesn't work, mean func never executes after initialization.

question not entirely clear me, suspect reason follows.

this

public delegatecommand logincommand => new delegatecommand(...)

is equivalent this

public delegatecommand logincommand { {return new delegatecommand(...)}}

so every time access logincommand property - returns new delegatecommand instance. means raisecanexecutechanged on fresh instance of command, , code called property before , can react change use own instances.

that's unlike first scenario there 1 instance of delegatecommand used everyone.


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