Warning CS0649 Field is never assigned to, and will always have its default value null .net maui

Question

Visual Studio shows a CS0649 error message on line 11: - "Warning CS0649 Field 'CalendarRangePickerPopupSelectedDates._onClosedPopup' is never assigned to, and will always have its default value null SampleApp (net6.0-maccatalyst) C:\Users\User\Documents\CalendarPluginMaui\SampleApp\Views\CalendarRangePickerPopupSelectedDates.xaml.cs 11 Active"

using MauiPopup.Views;  
using SampleApp.Model;  
using SampleApp.ViewModels;  
using System;  
  
namespace SampleApp.Views;  
  
public partial class CalendarRangePickerPopupSelectedDates : BasePopupPage  
{  
#pragma warning disable IDE0044 // Add readonly modifier   
    private Action<CalendarRangePickerResult> _onClosedPopup;   // CS0649 Error occurs here at "_onClosedPopup"  
#pragma warning restore IDE0044 // Add readonly modifier  
    public CalendarRangePickerPopupSelectedDates()  
 {  
        MauiPopup.PopupAction.DisplayPopup(new CalendarRangePickerPopupSelectedDates());  
  
        InitializeComponent();  
  
        MauiPopup.PopupAction.ClosePopup();  
    }  
    protected override void OnAppearing()  
    {  
        base.OnAppearing();  
  
        if (BindingContext is CalendarRangePickerPopupSelectedDatesViewModel vm)  
            vm.Closed += _onClosedPopup;  
    }  
  
    protected override void OnDisappearing()  
    {  
        if (BindingContext is CalendarRangePickerPopupSelectedDatesViewModel vm)  
            vm.Closed -= _onClosedPopup;  
  
        base.OnDisappearing();  
    }  
}  

I also tried to decorate the field with the nullable reference, but it did not work: -

    disable nullable  
     private Action<CalendarRangePickerResult>? _onClosedPopup;  
    restore nullable  

Any assistance will be greatly appreciated.

Answer 1

I updated the code, change the null references and the issue seemed to be fixed: -

using MauiPopup.Views;  
using SampleApp.Model;  
using SampleApp.ViewModels;  
using System;  
  
namespace SampleApp.Views;  
  
public partial class CalendarRangePickerPopupSelectedDates : BasePopupPage  
{  
#pragma warning disable CS8632 // The annotation for nullable reference types should only be used in code within a '#nullable' annotations context.  
    private readonly Action<CalendarRangePickerResult>? _onClosedPopup;  
  
    public CalendarRangePickerPopupSelectedDates()  
    {  
    }  
#pragma warning restore CS8632 // The annotation for nullable reference types should only be used in code within a '#nullable' annotations context.  
    public CalendarRangePickerPopupSelectedDates(Action<CalendarRangePickerResult> onClosedPopup)  
	{  
        _onClosedPopup = onClosedPopup;         
  
        InitializeComponent();  
          
    }  
    protected override void OnAppearing()  
    {  
        base.OnAppearing();  
  
        if (BindingContext is CalendarRangePickerPopupSelectedDatesViewModel vm)  
            vm.Closed += _onClosedPopup;  
    }  
  
    protected override void OnDisappearing()  
    {  
        if (BindingContext is CalendarRangePickerPopupSelectedDatesViewModel vm)  
            vm.Closed -= _onClosedPopup;  
  
        base.OnDisappearing();  
    }  
}