How to implement the datagrid editing function if the tables are merged?

Question

C++ / C#

I am working on WPF C# visual studio.
I need to display two tables in one (I did it). After that, you need to edit the contents of the table, I have a form in a new window to add new data, I want to use it for editing. But I don’t know how to pass values ​​​​to it, before I combined the tables everything worked fine.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace YchetApparatov
{
    /// <summary>
    /// Логика взаимодействия для CabinetPage.xaml
    /// </summary>
    public partial class CabinetPage : Page
    {
        NormApparatYchetEntities2 dataEntetis = new NormApparatYchetEntities2();
        
        public CabinetPage()
        {
            InitializeComponent();
            DGCabinetViev.ItemsSource = NormApparatYchetEntities2.GetContext().CabinetTable.ToList();
           var query =
            from SpCab in dataEntetis.CabinetTable
            orderby SpCab.IdPolzovatel
            select new
            {
                SpCab.IdPolzovatel,
                SpCab.NomerCabineta,
                SpCab.PolzovatelTable.Name,
                SpCab.IdComplect,
            };
            DGCabinetViev.ItemsSource = query.ToList();

        }

        private void UpdateCabinetClick(object sender, RoutedEventArgs e)
        {
            DGCabinetViev.ItemsSource = NormApparatYchetEntities2.GetContext().CabinetTable.ToList();
            var query =
             from SpCab in dataEntetis.CabinetTable
             orderby SpCab.IdPolzovatel
             select new
             {
                 SpCab.IdPolzovatel,
                 SpCab.NomerCabineta,
                 SpCab.PolzovatelTable.Name,
                 SpCab.IdComplect,
             };
            DGCabinetViev.ItemsSource = query.ToList();
        }

        private void DeleteCabinetClick(object sender, RoutedEventArgs e)
        {
            var cabinetremoving = DGCabinetViev.SelectedItems.Cast<CabinetTable>().ToList();

            if (MessageBox.Show($" вы точно хотите удалить следующие {cabinetremoving.Count()} элементов?", "внимание",
                    MessageBoxButton.YesNo, MessageBoxImage.Question) == MessageBoxResult.Yes)

                try
                {
                    NormApparatYchetEntities2.GetContext().CabinetTable.RemoveRange(cabinetremoving);
                    NormApparatYchetEntities2.GetContext().SaveChanges();
                    MessageBox.Show("данные удалены");

                    DGCabinetViev.ItemsSource = NormApparatYchetEntities2.GetContext().CabinetTable.ToList();
                }


                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message.ToString());
                }
        }

        private void AddNewCabinetClick(object sender, RoutedEventArgs e)
        {
            AddCabinetWindow addnewcabinet = new AddCabinetWindow(null);
            addnewcabinet.Show();
        }

        private void BtnEdit_Click(object sender, RoutedEventArgs e)
        {
            AddCabinetWindow addnewcabinet = new AddCabinetWindow((sender as Button).DataContext as CabinetTable);
            addnewcabinet.Show();
        }

        private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
        {

        }
    }

}

XAML

<Page x:Class="YchetApparatov.CabinetPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:YchetApparatov"
      mc:Ignorable="d" 
      d:DesignHeight="720" d:DesignWidth="1280"
      Title="CabinetPage">

    <Grid Margin="0,97,0,34">
        <Grid.RowDefinitions>
        </Grid.RowDefinitions>
        <DataGrid x:Name="DGCabinetViev" AutoGenerateColumns="False" IsReadOnly="True" Margin="0,-3,0,126">

            <DataGrid.Columns>
                <DataGridTextColumn Header="Номер кабинета" Binding="{Binding NomerCabineta}" Width="*" ></DataGridTextColumn>
                <DataGridTextColumn Header="Айди пользователя" Binding="{Binding IdPolzovatel}"  Width="*"></DataGridTextColumn>
                <DataGridTextColumn Header="Имя пользователя" Binding="{Binding Name}"  Width="*"></DataGridTextColumn>

                <DataGridTextColumn Header="Айди комплекта" Binding="{Binding IdComplect}" Width="*"></DataGridTextColumn>
              
                <DataGridTemplateColumn>
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Button Content="Редактировать" Name="BtnEdit" Click="BtnEdit_Click" Canvas.Left="10" Canvas.Top="63" Width="107" Height="21"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>



            </DataGrid.Columns>



        </DataGrid>
        <Button x:Name="AddNewCabinet" HorizontalAlignment="Left" Margin="7,-94,0,0" VerticalAlignment="Top" Width="51" Background="{x:Null}" Click="AddNewCabinetClick" Height="45">
            <StackPanel Orientation="Horizontal" Height="45" Width="51">
                <Image Source="images/Plus.png" Margin="0,0,5,6" Width="46" />

            </StackPanel>
        </Button>
        <Button x:Name="DeleteCabinet" HorizontalAlignment="Left" Margin="63,-94,0,0" VerticalAlignment="Top" Width="57" Click="DeleteCabinetClick" Background="{x:Null}" Height="45">
            <StackPanel Orientation="Horizontal" Height="45" Width="51">
                <Image Source="images/Krestik.png" Margin="0,0,5,5" Width="48" />

            </StackPanel>
        </Button>
        <Button Content="Очистить" HorizontalAlignment="Left" Margin="0,-30,0,0" VerticalAlignment="Top" Width="75"/>
        <TextBox HorizontalAlignment="Left" Height="22" Margin="88,-30,0,0" TextWrapping="Wrap" Text="" VerticalAlignment="Top" Width="165" TextChanged="TextBox_TextChanged"/>
        <Label Content="Фильтр" HorizontalAlignment="Left" Margin="0,-55,0,0" VerticalAlignment="Top" Height="25" Width="63"/>
        <Label Content="Поиск" HorizontalAlignment="Left" Margin="88,-55,0,0" VerticalAlignment="Top" Height="25" Width="63"/>
        <Button x:Name="UpdateCabinet" HorizontalAlignment="Left" Margin="125,-94,0,0" VerticalAlignment="Top" Width="51" Background="{x:Null}" Click="UpdateCabinetClick" Height="45">
            <StackPanel Orientation="Horizontal" Height="45" Width="51">
                <Image Source="images/Update.png" Margin="0,0,5,0" Width="47" />

            </StackPanel>
        </Button>
    </Grid>
</Page>