kursovaya/AdminWindow.axaml.cs

using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Interactivity;
using Avalonia.Markup.Xaml;
using kursovaya.Models;

namespace kursovaya;

public partial class AdminWindow : Window
{
    List<Discipline> Disciplines = new List<Discipline>();
    List<Group> Groups = new List<Group>();
    List<Teacher> Teachers = new List<Teacher>();
    ObservableCollection<DisciplineGroupTeacher> DisciplineGroupTeachers = new ObservableCollection<DisciplineGroupTeacher>();
    public AdminWindow()
    {
        InitializeComponent();
        
        var ctx = new DatabaseContext();

        Disciplines = ctx.Disciplines.ToList();
        Groups = ctx.Groups.ToList();
        Teachers = ctx.Teachers.ToList();

        var disciplineTeachers = ctx.DisciplineTeachers.ToList();

        foreach (DisciplineTeacher disciplineTeacher in disciplineTeachers)
        {
            //todo
            //var group = 
            var teacher = ctx.Teachers.FirstOrDefault(t => t.Id == disciplineTeacher.IdTeacher);
            var discipline = ctx.Disciplines.FirstOrDefault(d => d.Id == disciplineTeacher.IdDiscipline);
            DisciplineGroupTeachers.Add(new DisciplineGroupTeacher(){Teacher = teacher, Discipline = discipline, Group = new Group() {Id = 777, YearAdmission = 777}});
        }
        
        GroupComboBox.ItemsSource = Groups.Select(g => g.Id);
        DisciplineComboBox.ItemsSource = Disciplines.Select(d => d.Name);
        TeacherComboBox.ItemsSource = Teachers.Select(t => t.Fio);
        FlatGrid.ItemsSource = DisciplineGroupTeachers;

    }

    public class DisciplineGroupTeacher()
    {
        public Group Group { get; set; }
        public Discipline Discipline { get; set; }
        public Teacher Teacher { get; set; }

        public string DisciplineName
        {
            get => Discipline.Name;
        }
        public string TeacherFio
        {
            get => Teacher.Fio;
        }
        public int GroupId
        {
            get => Group.Id;
        }
    }
    
    private void ButtonBack_OnClick(object? sender, RoutedEventArgs e)
    {
        Close();
    }
}