Realtime validtion

Eduardo Gomez 3,426 Reputation points
2021-10-05T01:00:39.267+00:00

Hello, I am trying137583-screenshot-2021-10-05-022028.png to validate a form and enable/disable a button

as you can see I am receiving my values

[AddINotifyPropertyChangedInterface]  
    public class LoginPageViewModel {  
  
        public ICommand OpenRegisterPopupCommand { get; set; }  
  
        public ICommand Register { get; set; }  
  
        public ICommand Login { get; set; }  
  
        public Users Users { get; set; }  
  
        public bool IsPopUpOpen { get; set; }  
  
        public LoginPageViewModel() {  
  
            Users = new Users();  
  
            Login = new Command(LoginAction, LoginAllowd);  
  
            Register = new Command(RegisterAction);  
  
            OpenRegisterPopupCommand = new Command(() => {  
                IsPopUpOpen = true;  
            });  
        }  
  
        private bool LoginAllowd() {  
           return !string.IsNullOrEmpty(Users.Email) && !string.IsNullOrEmpty(Users.Password);  
        }  
  
        private void LoginAction() {  
            throw new NotImplementedException();  
        }  

   <Grid  
            Padding="20"  
            x:DataType="vm:LoginPageViewModel"  
            RowDefinitions="120,Auto,*"  
            RowSpacing="20"  
            VerticalOptions="Center">  
  
            <ffimageloadingsvg:SvgCachedImage  
                HeightRequest="120"  
                Source="book.svg"  
                WidthRequest="120" />  
  
            <Frame  
                Grid.Row="1"  
                Padding="0"  
                BorderColor="Silver"  
                IsClippedToBounds="True"  
                VerticalOptions="FillAndExpand">  
                <StackLayout Padding="20">  
                    <Entry  
                        Placeholder="Email"  
                        Style="{StaticResource EntrySyle}"  
                        Text="{Binding Users.Email}" />  
  
                    <Entry  
                        Placeholder="Password"  
                        Style="{StaticResource EntrySyle}"  
                        Text="{Binding Users.Password}" />  
  
                    <Button Command="{Binding Login}" Text="Login"/>  
                </StackLayout>  
            </Frame>  
  
            <Label  
                Grid.Row="2"  
                HorizontalOptions="End"  
                Style="{StaticResource SignUpLabelStyle}"  
                Text="Do not ave an account? Sign up">  
                <Label.GestureRecognizers>  
                    <TapGestureRecognizer Command="{Binding OpenRegisterPopupCommand}" />  
                </Label.GestureRecognizers>  
            </Label>  
        </Grid>  
    </ScrollView>  


  [AddINotifyPropertyChangedInterface]  
    public class Users {  
        public string Id { get; set; }  
  
        public string Email { get; set; }  
  
        public string Password { get; set; }  
    }  
}  

Because I inject fody, I can see that my value gets an update as I type

137731-screenshot-2021-10-05-102506.png

By the way, in my ViewModel can see that the Users object is modified, so I do not understand
137773-screenshot-2021-10-05-163609.png

Xamarin
Xamarin
A Microsoft open-source app platform for building Android and iOS apps with .NET and C#.
5,325 questions
0 comments No comments
{count} votes

Accepted answer
  1. Leon Lu (Shanghai Wicresoft Co,.Ltd.) 71,926 Reputation points Microsoft Vendor
    2021-10-06T09:47:20.407+00:00

    Here is MainPage.xaml.

    <?xml version="1.0" encoding="utf-8" ?>
    <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
                 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
                 xmlns:vm="clr-namespace:App142"
                 x:Class="App142.MainPage">
    
        <StackLayout>
    
    
            <Grid
                 Padding="20"
    
                 RowDefinitions="120,Auto,*"
                 RowSpacing="20"
                 VerticalOptions="Center">
    
    
                <Frame
                     Grid.Row="1"
                     Padding="0"
                     BorderColor="Silver"
                     IsClippedToBounds="True"
                     VerticalOptions="FillAndExpand">
                    <StackLayout Padding="20">
                        <Entry
                             Placeholder="Email"
    
                             Text="{Binding Users.Email}" />
    
                        <Entry
                             Placeholder="Password"
    
                             Text="{Binding Users.Password}" />
    
                        <Button Command="{Binding Login}" Text="Login"/>
                    </StackLayout>
                </Frame>
    
                <Label
                     Grid.Row="2"
                     HorizontalOptions="End"
    
                     Text="Do not ave an account? Sign up">
                    <Label.GestureRecognizers>
                        <TapGestureRecognizer Command="{Binding OpenRegisterPopupCommand}" />
                    </Label.GestureRecognizers>
                </Label>
            </Grid>
        </StackLayout>
    
    </ContentPage>
    

    Here is MainPage.xaml.cs. Contains ViewModel and User model.

    using PropertyChanged;
    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;
    using System.Windows.Input;
    using Xamarin.Forms;
    
    namespace App142
    {
        public partial class MainPage : ContentPage
        {
            public MainPage()
            {
                InitializeComponent();
    
                BindingContext = new LoginPageViewModel();
            }
    
    
        }
        [AddINotifyPropertyChangedInterface]
        public class LoginPageViewModel
        {
    
    
    
            public ICommand OpenRegisterPopupCommand { get; set; }
    
            public ICommand Register { get; set; }
    
            public ICommand Login { get; set; }
    
            public Users Users { get; set; }
    
            public bool IsPopUpOpen { get; set; }
    
            public LoginPageViewModel()
            {
    
                Users = new Users();
                Users.PropertyChanged += OnUserEditPropertyChanged;
                Login = new Command(LoginAction, LoginAllowd);
    
                Register = new Command(RegisterAction);
    
                OpenRegisterPopupCommand = new Command(() => {
                    IsPopUpOpen = true;
                });
            }
    
    
    
            void OnUserEditPropertyChanged(object sender, PropertyChangedEventArgs args)
            {
                (Login as Command).ChangeCanExecute();
            }
            private bool LoginAllowd()
            {
                return !string.IsNullOrEmpty(Users.Email) && !string.IsNullOrEmpty(Users.Password);
            }
    
            private void LoginAction()
            {
    
            }
            private void RegisterAction()
            {
    
            }
    
    
        }
        [AddINotifyPropertyChangedInterface]
        public class Users: INotifyPropertyChanged
        {
            public event PropertyChangedEventHandler PropertyChanged;
            public string Id { get; set; }
    
            public string Email { get; set; }
    
            public string Password { get; set; }
        }
    
    
    }
    

1 additional answer

Sort by: Most helpful
  1. Leon Lu (Shanghai Wicresoft Co,.Ltd.) 71,926 Reputation points Microsoft Vendor
    2021-10-06T02:48:58.867+00:00

    Hello,​

    Welcome to our Microsoft Q&A platform!

    You can add Users.PropertyChanged += OnUserEditPropertyChanged; below Users = new Users();, then add OnUserEditPropertyChanged method in your LoginPageViewModel.cs

       void OnUserEditPropertyChanged(object sender, PropertyChangedEventArgs args)  
               {  
                   (Login as Command).ChangeCanExecute();  
               }  
    

    When you user‘s property be changed, LoginAllowd method will be executed to judge the value is !string.IsNullOrEmpty(Users.Email) && !string.IsNullOrEmpty(Users.Password);

    137903-image.png 137899-image.png

    For more information about Command, you can refer to this thread:
    https://learn.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/data-binding/commanding#basic-commanding

    Best Regards,

    Leon Lu


    If the response is helpful, please click "Accept Answer" and upvote it.

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.