Insert data to Firebase and set restriction to UI(username and password) in xamarin form

Question

I have create acc page in xamarin form. The fields are basic info for customer like firstname, lastname and I have field "username" and "password". So it goes like this. I want to set a rule for;

1. Username; -no duplication for username. Because every username inputted by customer, It check in database if that username is avail or not. Example, username: dummy123

I want this way for username; -upon tapping the entry field for username, and assume customer will input "dummy123" a toast will appear like "username already exist"

2. Password; -password must contain; capital letter, small char, special char, number and 8 letter and above.

I want this way for password; -upon tapping the entry field for password, and assume customer will input "@imcool123" a toast will appear like this; "password must contain capital letter, small char, special char, number and 8 letter and above"

any link posted will be appreciated. Thank you so much.

Answer 1

You can follow the steps below to make your ideas work.

First, you can create a model for deserializing your response.

 public class Person  
    {  
        public string Name { get; set; }  
    }  

Second, you can write the code to connect the Firebase Realtime Database.

using Firebase.Database;  
using Firebase.Database.Query;  
  
FirebaseClient firebase = new FirebaseClient("https://");  

Third, create an Entry with TextChanged in the MainPage.xaml.

 <StackLayout>
        <Entry x:Name="EntryText" TextChanged="EntryText_TextChanged" />
 </StackLayout>

Fourth, fulfill the EntryText_TextChanged method in MainPage.xaml.cs. The method provide a way to match the data which in the Firebase.

 public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
        }
 
 public async Task<List<Person>> GetAllPersons()  
    {  

        return (await firebase  
          .Child("Persons")  
          .OnceAsync<Person>()).Select(item => new Person  
          {  
              Name = item.Object.Name,  
              PersonId = item.Object.PersonId  
          }).ToList();  
    }  

        private void EntryText_TextChanged(object sender, TextChangedEventArgs e)
        {
            var oldText = e.OldTextValue;
            var newText = e.NewTextValue;

            var person = await firebaseHelper.GetPerson(Convert.ToString(EntryText.Text);
            if (person != null)
            {
                
                EntryText.Text = person.Name;
                // this is a Toast method
                await DependencyService.Get<IToast>().ShortAlert("username already exist");

            }
            else
            {
                
            }
        }
// This is the method to find the name if it has existed
        public async Task<Person> GetPerson(string personName)
        {
            var allPersons = await GetAllPersons();
            await firebase
              .Child("Persons")
              .OnceAsync<Person>();
            return allPersons.Where(a => a.PersonName == personName).FirstOrDefault();
        }
    }

In addition, here is the information about the Xamarin.Forms - How To Make Toast Message Using Dependency Service. You can check this article.