AwaitableMessages.cs

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

namespace MongoDBApp.Utility
{
    public class AwaitableMessages
    {
        public static Task<T> NextMessageAsync<T>()
        {
            var tcs = new TaskCompletionSource<T>();
            Messenger.Default.Register<T>(null, item => tcs.TrySetResult(item));
            return tcs.Task;
        }
    }
}

CustomerOrderDetailsViewModel.cs

using MongoDBApp.Models;
using MongoDBApp.Services;
using MongoDBApp.Utility;
using PropertyChanged;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MongoDBApp.Extensions;
using System.Windows.Input;
using MongoDBApp.Common;
using MongoDBApp.Messages;

namespace MongoDBApp.ViewModels
{
    [ImplementPropertyChanged]
    public class CustomerOrdersViewModel : IPageViewModel
    {


        private IDataService<OrderModel> _orderDataService;
        public ICommand SaveCommand { get; set; }
        public ICommand EditCommand { get; set; }
        public ICommand WindowLoadedCommand { get; set; }
        private IDialogService _dialogService; 

        public CustomerOrdersViewModel(IDataService<OrderModel> orderDataService, IDialogService dialogservice)
        {
 
            this._orderDataService = orderDataService;
            this._dialogService = dialogservice;
                    
            Messenger.Default.Register<ProductModel>(this, OnUpdateProductMessageReceived);

            LoadCommands();

           
        }


        

        #region properties

        public string SelectedCustomerEmail { get; set; }

        public ObservableCollection<OrderModel> CustomerOrders { get; set; }

        public OrderModel SelectedOrder { get; set; }

        public ProductModel SelectedProduct { get; set; }

        public Task Initialization { get; set; }

        public bool IsEnabled { get; set; }
        
        public string Name
        {
            get
            {
                return "Order Details";
            }
        }

       
        #endregion



        #region methods

        private void OnUpdateProductMessageReceived(ProductModel product)
        {
            SelectedProduct = product;
            _dialogService.CloseDetailDialog();
        }

        private void LoadCommands()
        {
            SaveCommand = new CustomCommand((c) => SaveCustomerAsync(c).FireAndLogErrors(), CanSaveOrder);
            EditCommand = new CustomCommand(EditOrder, CanModifyOrder);
            WindowLoadedCommand = new CustomCommand((c) => WindowLoadedAsync(c).FireAndLogErrors(), CanLoadWindow);
        }


        private bool CanSaveOrder(object obj)
        {
            if (SelectedOrder != null && SelectedOrder.Email != null && SelectedOrder.Date != null &&
                SelectedOrder.Id != null)
            {
                return true;
            }

            return false;
        }


        private bool CanModifyOrder(object obj)
        {

            if (SelectedOrder != null && SelectedOrder.Email != null && SelectedOrder.Date != null &&
                SelectedOrder.Id != null && SelectedProduct != null )
            {
                return true;
            }

            return false;
        }


        private void EditOrder(object obj)
        {
            Messenger.Default.Send<ProductModel>(SelectedProduct);
            _dialogService.ShowDetailDialog();         
        }


        private bool CanLoadWindow(object obj)
        {
            return true;
        }

        private async Task WindowLoadedAsync(object obj)
        {
            await InitializeAsync();
            this.Initialization = InitializeAsync();
        }




        private async Task InitializeAsync()
        {
            var customer = await AwaitableMessages.NextMessageAsync<CustomerModel>();
            SelectedCustomerEmail = customer.Email;
            await LoadCustomerOrdersAsync(SelectedCustomerEmail);
            IsEnabled = true;
        }


       

        public async Task LoadCustomerOrdersAsync(string email)
        {
            var ordersResult = await _orderDataService.GetAllByEmailAsync(email);
            CustomerOrders = ordersResult.ToObservableCollection();
        }


        private async Task SaveCustomerAsync(object customer)
        {

            if (SelectedOrder != null)
            {
                IsEnabled = true;
                await Task.Run(() => _orderDataService.UpdateAsync(SelectedOrder));
                IsEnabled = false;
            }

            return;
        }
        
        #endregion
    }
}

CustomerOrdersView.xaml

<UserControl x:Class="MongoDBApp.Views.CustomerOrdersView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:boolean_converter="clr-namespace:MongoDBApp.Converters"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"
             d:DesignHeight="300"
             d:DesignWidth="300"
             mc:Ignorable="d">

    <UserControl.Resources>
        <boolean_converter:BooleanConverter x:Key="BooleanConverter" />
    </UserControl.Resources>

    <Viewbox>
        <xctk:BusyIndicator IsBusy="{Binding ButtonEnabled}">

            <Grid>
                <Grid>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*" />
                        <RowDefinition Height="2*" />
                        <RowDefinition Height="1*" />
                        <RowDefinition Height="1*" />
                        <RowDefinition Height="1*" />
                        <RowDefinition Height="1*" />
                        <RowDefinition Height="1*" />
                        <RowDefinition Height="1*" />
                        <RowDefinition Height="1*" />
                    </Grid.RowDefinitions>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="1*" />
                        <ColumnDefinition Width="1*" />
                        <ColumnDefinition Width="2*" />
                        <ColumnDefinition Width="1*" />
                        <ColumnDefinition Width="2*" />
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>


                    <i:Interaction.Triggers>
                        <i:EventTrigger EventName="Loaded">
                            <i:InvokeCommandAction Command="{Binding WindowLoadedCommand}" />
                        </i:EventTrigger>
                    </i:Interaction.Triggers>

                    <DataGrid x:Name="customersgrid"
                              Grid.Row="0"
                              Grid.RowSpan="3"
                              Grid.Column="1"
                              Grid.ColumnSpan="4"
                              AutoGenerateColumns="False"
                              ItemsSource="{Binding CustomerOrders}"
                              SelectedItem="{Binding SelectedOrder}">
                        <DataGrid.Columns>
                            <DataGridTextColumn Binding="{Binding Email}" Header="Email" />
                            <DataGridTextColumn Binding="{Binding Date}" Header="Date" />
                            <DataGridTextColumn Binding="{Binding Status}" Header="Shipping Status" />
                        </DataGrid.Columns>
                    </DataGrid>
                    <Label Grid.Row="4"
                           Grid.Column="1"
                           HorizontalAlignment="Left"
                           VerticalAlignment="Top"
                           Content="Date:" />


                    <TextBlock Grid.Row="4"
                               Grid.Column="2"
                               HorizontalAlignment="Left"
                               VerticalAlignment="Top"
                               Text="{Binding SelectedOrder.Date}"
                               TextWrapping="Wrap" />
                    <Label Grid.Row="4"
                           Grid.Column="3"
                           HorizontalAlignment="Left"
                           VerticalAlignment="Top"
                           Content="Products:" />
                    <ComboBox Grid.Row="4"
                              Grid.Column="4"
                              Grid.ColumnSpan="4"
                              Width="120"
                              HorizontalAlignment="Left"
                              VerticalAlignment="Top"
                              DisplayMemberPath="ProductId"
                              ItemsSource="{Binding SelectedOrder.Products}"
                              ScrollViewer.VerticalScrollBarVisibility="Visible"
                              SelectedItem="{Binding SelectedProduct}" />
                    <Label Grid.Row="5"
                           Grid.Column="1"
                           HorizontalAlignment="Left"
                           VerticalAlignment="Top"
                           Content="Email:" />


                    <TextBlock Grid.Row="5"
                               Grid.Column="2"
                               HorizontalAlignment="Left"
                               VerticalAlignment="Top"
                               Text="{Binding SelectedOrder.Email}"
                               TextWrapping="Wrap" />
                    <RadioButton Grid.Row="5"
                                 Grid.Column="3"
                                 Grid.ColumnSpan="2"
                                 HorizontalAlignment="Left"
                                 VerticalAlignment="Top"
                                 Content="Shipped"
                                 IsChecked="{Binding SelectedOrder.Status,
                                                     Converter={StaticResource BooleanConverter},
                                                     ConverterParameter='true',
                                                     Mode=TwoWay}" />

                    <RadioButton Grid.Row="5"
                                 Grid.Column="4"
                                 Grid.ColumnSpan="2"
                                 HorizontalAlignment="Left"
                                 VerticalAlignment="Top"
                                 Content="Processing"
                                 IsChecked="{Binding SelectedOrder.Status,
                                                     Converter={StaticResource BooleanConverter},
                                                     ConverterParameter='false',
                                                     Mode=TwoWay}" />


                    <Button Grid.Row="7"
                            Grid.Column="3"
                            Grid.ColumnSpan="3"
                            Width="75"
                            HorizontalAlignment="Left"
                            VerticalAlignment="Top"
                            Command="{Binding EditCommand}"
                            Content="Edit"
                            IsEnabled="{Binding IsEnabled}" />
                    <Button Grid.Row="7"
                            Grid.Column="3"
                            Grid.ColumnSpan="3"
                            Width="75"
                            HorizontalAlignment="Center"
                            VerticalAlignment="Top"
                            Command="{Binding SaveCommand}"
                            Content="Save"
                            IsEnabled="{Binding IsEnabled}" />

                </Grid>
            </Grid>
        </xctk:BusyIndicator>
    </Viewbox>
</UserControl>