Xaramin form -calling variable from other .cs file - xamarin.forms

Question

I am doing a quiz game in Xaramin. forms. and for the score function. if the user got a correct answer, I want the score will add 1.but in my case even the give the correct answer, the score is not adding.
I am also trying to bind to the "score" variable to a label. I want to know if i put a correct code or not.
Button
private void submit_Clicked(object sender, EventArgs e)
{
string answer = this.answer.Text;
string canswer = "correct";
if (answer != null)
{
string ranswer = answer.Replace(" ", string.Empty);
if (ranswer.ToLower() == canswer)
{
DisplayAlert("GoodJob", "You got the correct answer", "OK");
bindingModel b = new bindingModel();
b.score++;
(sender as Button).IsEnabled = false;
}
else
{
DisplayAlert("Unfortunately", "Your answer is wrong", "OK");
(sender as Button).IsEnabled = false;
}
}
}
ViewModel
public class bindingModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public int displayScore => Score;
public int score = 0;
void OnPropertyChanged(int score)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(score.ToString()));
}
public int Score
{
get => score;
set
{
if (score != value)
{
score = value;
OnPropertyChanged(score);
}
}
}
}
Model
<Label Text="{Binding Score}"/>

Answer 1

in your page constructor, keep a reference to your VM
bindingModel VM;
// this is your constructor, the name will match your page name
public MyPage()
{
InitializeComponent();
this.BindingContext = VM = new bindingModel();
...
}
then in your event handler, you do NOT need to create a new bindingModel
// update the Count on the VM
VM.Count++;

Answer 2

Answer
There's two things broken here:
You are re-initializing your ViewModel instead of referencing the same instance
You are passing the wrong value into PropertyChangedEventArgs
1. Referencing the View Model
You are re-initializing the ViewModel every time by calling bindingModel b = new bindingModel();
Lets initialize the ViewModel once, store it as a field, set it as the BindingContext for our ContentPage, and reference that field in submit_Clicked
public partial class QuizPage : ContentPage
{
readonly bindingModel _bindingModel;
public QuizPage()
{
_bindingModel = new bindingModel();
BindingContext = _bindingModel;
}
private async void submit_Clicked(object sender, EventArgs e)
{
string answer = this.answer.Text;
string canswer = "correct";
Button button = (Button)sender;
if (answer != null)
{
string ranswer = answer.Replace(" ", string.Empty);
if (ranswer.ToLower() == canswer)
{
await DisplayAlert("GoodJob", "You got the correct answer", "OK");
_bindingModel.score++;
button.IsEnabled = false;
}
else
{
await DisplayAlert("Unfortunately", "Your answer is wrong", "OK");
button.IsEnabled = false;
}
}
}
}
2. PropertyChangedEventArgs
You need to pass in the name of the property to PropertyChangedEventArgs.
They way PropertyChanged works is that it announces the name of the property that has changed. In this case, it needs to broadcast that the Score property has changed.
Let's use nameof(Score) to pass in the string "Score" to PropertyChangedEventArgs:
void OnScorePropertyChanged()
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(displayScore)));
}
public int Score
{
get => score;
set
{
if (score != value)
{
score = value;
OnScorePropertyChanged();
}
}
}