c#

  <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="2*"/>
            <ColumnDefinition Width="3*"/>
        </Grid.ColumnDefinitions>

        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <ComboBox Grid.Row="0" Grid.Column="0" SelectedItem="{Binding SelectedStudent}" ItemsSource="{Binding Studenti}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Jmeno}" />
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
        <TextBlock Grid.Row="0" Grid.Column="1" Text="Ahoj" />
        <ListBox Grid.Row="1" Grid.Column="1"  ItemsSource="{Binding Polozky}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel>
                        <TextBlock Text="{Binding Datum}" />
                        <TextBlock Text="{Binding Id}" />
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

        <DataGrid Grid.Row="0" Grid.Column="2" Grid.RowSpan="3" ItemsSource="{Binding Polozky}" />
    </Grid>

   public class Polozka
    {
        public DateTime Datum { get; set; }
        public int Id { get; set; }

        public Polozka(int id)
        {
            Datum = DateTime.Now.AddHours(id);
            Id = id;
        }
    }

public class Data
    {
        public List<Polozka> Polozky { get; set; }
        public List<Student> Studenti { get; set; }
        public Student SelectedStudent { get; set; }

        public Data()
        {
            Polozky = new List<Polozka>()
            {
                new Polozka(1),
                new Polozka(2),
                new Polozka(3)
            };

            Studenti = new List<Student>()
            {
                new Student("Adam"),
                new Student("Alena"),
                new Student("Jirka"),
                new Student("Matúš"),
                new Student("Samuel")
            };

            SelectedStudent = Studenti.FirstOrDefault();
        }
    }

protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);

            Data data = new Data();

            MainWindow window = new MainWindow();
            window.DataContext = data;
            window.ShowDialog();

        }

public class Student
    {
        public string Jmeno { get; set; }

        public Student(string jmeno)
        {
            Jmeno = jmeno;
        }
    }