MainView.cs

using MongoDBApp.DAL;
using MongoDBApp.Models;
using MongoDBApp.Services;
using MongoDBApp.ViewModels;
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.Shapes;

namespace MongoDBApp.Views
{
    /// <summary>
    /// Interaction logic for MainView.xaml
    /// </summary>
    public partial class MainView : Window
    {
        private MainViewModel ViewModel { get; set; }
        private static ICustomerDataService customerDataService = new CustomerDataService(CustomerRepository.Instance);


        public MainView()
        {
            InitializeComponent();
            ViewModel = new MainViewModel(customerDataService); 
            this.DataContext = ViewModel;

        }

    }
}

MainView.xaml

<Window x:Class="MongoDBApp.Views.MainView"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:email_validator="clr-namespace:MongoDBApp.Validator"
        xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"
        Title="Orders Dashbord"
        Width="800"
        Height="500">

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

        <Grid>
            <TabControl>
                <TabItem Header="Customer">
                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="70" />
                            <RowDefinition Height="Auto" />
                            <RowDefinition Height="1*" />
                            <RowDefinition Height=".50*" />
                            <RowDefinition Height="1*" />
                            <RowDefinition Height="1*" />
                            <RowDefinition Height="1*" />
                            <RowDefinition Height="1*" />
                        </Grid.RowDefinitions>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width=".1*" />
                            <ColumnDefinition Width="1*" />
                            <ColumnDefinition Width="*" />
                            <ColumnDefinition Width="2*" />
                            <ColumnDefinition Width=".5*" />
                        </Grid.ColumnDefinitions>

                        <DataGrid x:Name="customersgrid"
                                  Grid.Row="0"
                                  Grid.RowSpan="3"
                                  Grid.Column="1"
                                  Grid.ColumnSpan="3"
                                  AutoGenerateColumns="False"
                                  ItemsSource="{Binding Customers}"
                                  SelectedItem="{Binding SelectedCustomer}">
                            <DataGrid.Columns>
                                <DataGridTextColumn Binding="{Binding Id}" Header="ID" />
                                <DataGridTextColumn Binding="{Binding FirstName}" Header="First Name" />
                                <DataGridTextColumn Binding="{Binding LastName}" Header="Last Name" />
                                <DataGridTextColumn Binding="{Binding Email}" Header="Email" />
                            </DataGrid.Columns>
                        </DataGrid>

                        <Label Grid.Row="4"
                               Grid.Column="1"
                               HorizontalAlignment="Center"
                               VerticalAlignment="Top"
                               Content="First Name:" />
                        <TextBox x:Name="fNameTbx"
                                 Grid.Row="4"
                                 Grid.Column="2"
                                 Grid.ColumnSpan="2"
                                 Width="120"
                                 Height="23"
                                 HorizontalAlignment="Left"
                                 VerticalAlignment="Top"
                                 Text="{Binding SelectedCustomer.FirstName}"
                                 TextWrapping="Wrap" />

                        <TextBlock x:Name="iDTbx"
                                   Grid.Row="4"
                                   Grid.Column="2"
                                   Grid.ColumnSpan="2"
                                   Width="180"
                                   Height="23"
                                   HorizontalAlignment="Right"
                                   VerticalAlignment="Top"
                                   Text="{Binding SelectedCustomer.Id}"
                                   TextWrapping="Wrap" />

                        <Label Grid.Row="4"
                               Grid.Column="3"
                               HorizontalAlignment="Left"
                               VerticalAlignment="Top"
                               Content="Customer ID:" />
                        <Label Grid.Row="5"
                               Grid.Column="1"
                               HorizontalAlignment="Center"
                               VerticalAlignment="Top"
                               Content="Last Name:" />
                        <TextBox x:Name="lNameTbx"
                                 Grid.Row="5"
                                 Grid.Column="2"
                                 Width="120"
                                 Height="23"
                                 HorizontalAlignment="Left"
                                 VerticalAlignment="Top"
                                 Text="{Binding SelectedCustomer.LastName}"
                                 TextWrapping="Wrap" />

                        <Label Grid.Row="6"
                               Grid.Column="1"
                               HorizontalAlignment="Center"
                               VerticalAlignment="Top"
                               Content="Email:" />

                        <TextBox x:Name="emailTbx"
                                 Grid.Row="6"
                                 Grid.Column="2"
                                 Grid.ColumnSpan="2"
                                 Width="120"
                                 Height="23"
                                 HorizontalAlignment="Left"
                                 VerticalAlignment="Top">
                            <Binding Path="SelectedCustomer.Email" UpdateSourceTrigger="PropertyChanged">
                                <Binding.ValidationRules>
                                    <email_validator:RegexValidationRule ValidationStep="RawProposedValue" />
                                </Binding.ValidationRules>
                            </Binding>
                        </TextBox>

                        <Button x:Name="addBtn"
                                Grid.Row="7"
                                Grid.Column="1"
                                Width="75"
                                HorizontalAlignment="Left"
                                VerticalAlignment="Top"
                                Command="{Binding CreateCommand}"
                                Content="Add" />

                        <Button x:Name="updateBtn"
                                Grid.Row="7"
                                Grid.Column="2"
                                Width="75"
                                HorizontalAlignment="Left"
                                VerticalAlignment="Top"
                                Command="{Binding UpdateCommand}"
                                Content="Update">

                            <Button.ToolTip>
                                <ToolTip>
                                    <StackPanel>
                                        <TextBlock><Run Text="Updates customer record" />
                                        </TextBlock>
                                    </StackPanel>
                                </ToolTip>
                            </Button.ToolTip>
                        </Button>

                        <Button x:Name="deleteBtn"
                                Grid.Row="7"
                                Grid.Column="3"
                                Width="75"
                                HorizontalAlignment="Left"
                                VerticalAlignment="Top"
                                Command="{Binding DeleteCommand}"
                                Content="Delete" />
                    </Grid>
                </TabItem>


                <TabItem Header="OrderStatus" />
                <TextBlock Width="100"
                           Height="100"
                           Text="TextBlock"
                           TextWrapping="Wrap" />


            </TabControl>
        </Grid>

    </xctk:BusyIndicator>

</Window>

MainViewModel.cs

using Microsoft.Practices.Prism.Commands;
using MongoDBApp.Common;
using MongoDBApp.Models;
using MongoDBApp.Services;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;
using MongoDBApp.Extensions;
using MongoDB.Bson;
using System.Windows.Input;

namespace MongoDBApp.ViewModels
{

    class MainViewModel : INotifyPropertyChanged
    {

        public ICommand UpdateCommand { get; set; }
        public ICommand CreateCommand { get; set; }
        public ICommand DeleteCommand { get; set; }

        public event PropertyChangedEventHandler PropertyChanged;
        private ICustomerDataService _customerDataService;


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




        public MainViewModel(ICustomerDataService customerDataService) 
        {
            this._customerDataService = customerDataService;
            QueryDataFromPersistence();

            UpdateCommand = new CustomCommand((c) => UpdateCustomerAsync(c).FireAndLogErrors(), CanModifyCustomer);
            DeleteCommand = new CustomCommand((c) => DeleteCustomerAsync(c).FireAndLogErrors(), CanModifyCustomer);
            CreateCommand = new CustomCommand((c) => AddCustomerAsync(c).FireAndLogErrors(), CanModifyCustomer);


        }


      #region Properties
       
        private MainViewModel selectedModel;
        public MainViewModel SelectedModel
        {
            get
            {
                return selectedModel;
            }
            set
            {
                selectedModel = value;
                RaisePropertyChanged("SelectedModel");
            }
        }




        private CustomerModel selectedCustomer;
        public CustomerModel SelectedCustomer
        {
            get
            {
                return selectedCustomer;
            }
            set
            {
                selectedCustomer = value;
                RaisePropertyChanged("SelectedCustomer");
            }
        }

       
        private ObservableCollection<CustomerModel> customers;
        public ObservableCollection<CustomerModel> Customers
        {
            get
            {
                return customers;
            }
            set
            {
                customers = value;
                RaisePropertyChanged("Customers");
            }
        }


        private Boolean button_enabled;
        public Boolean ButtonEnabled 
        {
            get { return button_enabled; }
            set
            {
                button_enabled = value;
                RaisePropertyChanged("ButtonEnabled");  
            }
        }



        private ObjectId _id;
        public ObjectId ID
        {
            get
            {
                return this._id;
            }
            set
            {
                this._id = value;
                RaisePropertyChanged("ID");
            }
        }
        
        
        private string firstName;
        public string FirstName
        {
            get
            {
                return this.firstName;
            }
            set
            {
                this.firstName = value;
                RaisePropertyChanged("FirstName");
            }
        }

        private string lastName;
        public string LastName
        {
            get
            {
                return this.lastName;
            }
            set
            {
                this.lastName = value;
                RaisePropertyChanged("LastName");
            }
        }



        private string email;
        public string Email
        {
            get
            {
                return this.email;
            }
            set
            {
                this.email = value;
                RaisePropertyChanged("Email");
            }
        }
        

      #endregion


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

        #region persistence methods

        private void QueryDataFromPersistence()
        {
            Customers =  _customerDataService.GetAllCustomers().ToObservableCollection();
        }

        private async Task UpdateCustomerAsync(object customer) { 
            
            ButtonEnabled = true;
            await Task.Run(() => _customerDataService.UpdateCustomer(selectedCustomer));
            ButtonEnabled = false; 
        }


        private async Task DeleteCustomerAsync(object customer)
        {
            ButtonEnabled = true;
            await Task.Run(() => _customerDataService.DeleteCustomer(selectedCustomer));
            ButtonEnabled = false;
        }

        private async Task AddCustomerAsync(object customer)
        {
            ButtonEnabled = true;
            await Task.Run(() => _customerDataService.AddCustomer(new CustomerModel()));
            ButtonEnabled = false;
        }

        #endregion


    }
}