<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="wpfTest1.MainWindow"
        xmlns:local="clr-namespace:wpfTest1"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <local:MyData x:Key="myData"/>
        <DataTemplate x:Key="tabTemplate">
            <StackPanel DataContext="{StaticResource myData}">
                <TextBox Text="{Binding Value1}"/>
                <TextBox Text="{Binding Value2}"/>
            </StackPanel>
        </DataTemplate>
    </Window.Resources>
    <Grid>
        <TabControl x:Name="tbPanel" SelectionChanged="tbPanel_SelectionChanged">
            <TabItem Header="Object A" ContentTemplate="{StaticResource tabTemplate}" />
            <TabItem Header="Object B" ContentTemplate="{StaticResource tabTemplate}" />
        </TabControl>
    </Grid>
</Window>

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 wpfTest1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        MyData myData = null;

        MyData objectA = new MyData();
        MyData objectB = new MyData();

        public MainWindow()
        {
            InitializeComponent();

            myData = ((MyData)this.Resources["myData"]);

            if (myData == null)
            {
                Application.Current.Shutdown();
            }

        }

        private void tbPanel_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            TabItem t = (TabItem)tbPanel.SelectedItem;
            if (t.Header.ToString() == "Object A")
            {
                objectB.LoadDataFromObject(myData);
                myData.LoadDataFromObject(objectA);
            }
            else if (t.Header.ToString() == "Object B")
            {
                objectA.LoadDataFromObject(myData);
                myData.LoadDataFromObject(objectB);
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace wpfTest1
{
    public class MyData : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        int value1 = 0, value2 = 0;

        public int Value1
        {
            get { return value1; }
            set
            {
                if (value1 != value)
                {
                    value1 = value;
                    NotifyProperyChanged("Value1");
                }
            }
        }

        public int Value2
        {
            get { return value2; }
            set
            {
                if (value2 != value)
                {
                    value2 = value;
                    NotifyProperyChanged("Value2");
                }
            }
        }

        private void NotifyProperyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public void LoadDataFromObject(MyData m)
        {
            this.Value1 = m.Value1;
            this.Value2 = m.Value2;
        }

        public MyData() { }
    }
}