AddingDeletingEditingData/DatabaseMVVMApp/ViewModels/AddCourseViewModel.cs

using System;
using System.Collections.Generic;
using Avalonia.Controls;
using DatabaseMVVMApp.Models;
using Microsoft.EntityFrameworkCore;
using ReactiveUI;
using Tmds.DBus.Protocol;

namespace DatabaseMVVMApp.ViewModels
{
	public class AddCourseViewModel : ReactiveObject
	{
        Course? _newCourse;
        string _errorText;
        bool _errorVisibility;
        UserControl _teacherControl;
        int? _duration;


        public int? Duration
        {
            get => _duration; 
            set => this.RaiseAndSetIfChanged(ref _duration, value);
        }

        public UserControl TeacherControl
        {
            get => _teacherControl;
            set => this.RaiseAndSetIfChanged(ref _teacherControl, value);
        }

        public Course? NewCourse
        { 
            get => _newCourse; 
            set => this.RaiseAndSetIfChanged(ref _newCourse, value);
        }

        public AddCourseViewModel() 
        {
            _newCourse = new Course();
            TeacherControl = new AddTeacher();
        }

        public AddCourseViewModel(UserControl control) 
        {
            _newCourse = new Course();
            TeacherControl = control;
        }

        public string ErrorText 
        {
            get => _errorText;
            set => this.RaiseAndSetIfChanged(ref _errorText, value);
        }

        public bool ErrorVisibility
        {
            get => _errorVisibility;
            set => this.RaiseAndSetIfChanged(ref _errorVisibility, value);
        }

        public void ToAddTeacherPage()
        {
            MainWindowViewModel.Instance.Control = TeacherControl;
        }

        public void AddCourse() 
        {
            if (NewCourse.Title == null || NewCourse.Title == "")
            {
                ErrorText = "Ó íîâîãî êóðñà äîëæíî áûòü íàçâàíèå";
                ErrorVisibility = true;
            }
            else if (Duration == null)
            {
                ErrorText = "Ââåäåíà íåêîððåêòíàÿ ïðîäîëæèòåëüíîñòü";
                ErrorVisibility = true;
            }
            else 
            {
                ErrorVisibility = false;
                MainWindowViewModel.connection.Courses.Add(NewCourse);
                string message = "Íîâûé êóðñ óñïåøíî äîáàâëåí";
                MainWindowViewModel.connection.SaveChanges();

                MainWindowViewModel.Instance.AddTeacherVM.AddCourse(NewCourse, Duration);
                MainWindowViewModel.Instance.Control = TeacherControl;
                MainWindowViewModel.MakeNotification(message);
            }
        }


    }
}