connect_base/AvaloniaApplication5/ViewModels/AddPageViewModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Data;
using AvaloniaApplication5.Models;
using Microsoft.EntityFrameworkCore;
using ReactiveUI;

namespace AvaloniaApplication5.ViewModels
{
	internal class AddPageViewModel : ViewModelBase
    {
		Teacher? _newTeacher;

		public List<TeacherCourse> TeacherCourses { get => _teacherCourses; set => this.RaiseAndSetIfChanged(ref _teacherCourses, value); }
        public Teacher? NewTeacher { get => _newTeacher; set => this.RaiseAndSetIfChanged(ref _newTeacher, value); }
	    public AddPageViewModel()
		{
			_newTeacher = new Teacher()
			{
				Gender = new Gender() 
			};
		}
		public AddPageViewModel(int id)
		{
			_newTeacher = MainWindowViewModel.myConnection.Teachers.Include(x=>x.Gender).Include(x=>x.TeacherCourses).ThenInclude(x=>x.Course).Include(x=>x.TeacherDisciplines).ThenInclude(x=>x.Discipline).FirstOrDefault(x=>x.Id == id);
            TeacherCourses = NewTeacher.TeacherCourses.ToList();
		}
	    public List<Gender> Genders => MainWindowViewModel.myConnection.Genders.ToList();
	    public List<Discipline> Disciplines => MainWindowViewModel.myConnection.Disciplines.ToList();
	    public List<Course> Courses => MainWindowViewModel.myConnection.Courses.ToList();
		List<TeacherCourse>? _teacherCourses;
		List<TeacherDiscipline>? _teacherDisciplines;
		public List<TeacherDiscipline> TeacherDisciplines { get => _teacherDisciplines; set => this.RaiseAndSetIfChanged(ref _teacherDisciplines, value); }
		Course? selectedCourse;
		Discipline? selectedDiscipline;
	    public Course? SelectedCourse
		{
			get => null;
			set
			{
				if(value != null)
				{
					NewTeacher.TeacherCourses.Add(new TeacherCourse()
					{
						Teacher = NewTeacher, Course = value
					});
					TeacherCourses = NewTeacher.TeacherCourses.ToList();
					this.RaisePropertyChanged(nameof(Courses));
				}
			}
		}
		public Discipline? SelectedDiscipline
		{
			get => null;
			set
			{
				if (value != null)
				{
					NewTeacher.TeacherDisciplines.Add(new TeacherDiscipline()
					{
						Teacher = NewTeacher, Discipline = value
					});
					TeacherDisciplines = NewTeacher.TeacherDisciplines.ToList();
					this.RaisePropertyChanged(nameof(Disciplines));
				}
			}
		}

       

		public void DeleteDiscipline(int id)
		{
			NewTeacher.TeacherDisciplines.Remove(NewTeacher.TeacherDisciplines.FirstOrDefault(x => x.Id == id));
			TeacherDisciplines = NewTeacher.TeacherDisciplines.ToList();
            this.RaisePropertyChanged(nameof(Disciplines));
        }

        public void AddTeacher()
		{
			if(NewTeacher.Id == 0)
			{
				MainWindowViewModel.myConnection.Teachers.Add(NewTeacher);
			}
			MainWindowViewModel.myConnection.SaveChanges();	
		}
    }
}