AdminServiceFilter.cs

using Microsoft.WindowsAzure.MobileServices;
using System;
using Windows.Foundation;

namespace MobileServices
{
    public class AdminServiceFilter : IServiceFilter
    {
        private bool disableScripts;
        private string masterKey;

        public AdminServiceFilter(bool disableScripts, string masterKey)
        {
            this.disableScripts = disableScripts;
            this.masterKey = masterKey;
        }

        public IAsyncOperation<IServiceFilterResponse> Handle(IServiceFilterRequest request, IServiceFilterContinuation continuation)
        {
            // Add master key to the request's header to have admin level control
            request.Headers["X-ZUMO-MASTER"] = this.masterKey;

            if (this.disableScripts)
            {
                // Get the request's query and append noScript=true as the first query parameter
                var uriBuilder = new UriBuilder(request.Uri);
                var oldQuery = (uriBuilder.Query ?? string.Empty).Trim('?');

                uriBuilder.Query = ("noScript=true&" + oldQuery).Trim('&');

                request.Uri = uriBuilder.Uri;
            }

            return continuation.Handle(request);
        }
    }
}

GetTableItems.cs

        public async Task<IJsonValue> GetTableItems(string tableName, string masterKey, bool disableServerSideScripts)
        {
            // Get mobile service client with the admin filter.
            MobileServiceClient adminMobileService = App.MobileService.WithFilter(new AdminServiceFilter(disableServerSideScripts, masterKey));

            // Get the selected mobile service table.
            IMobileServiceTable mobileServiceTable = this.adminMobileService.GetTable(tableName);

            // Read the first 10 items in this table,
            // With disableServerSideScripts=true it's the actual first 10 rows otherwise it depends on the server side script.
            return await mobileServiceTable.ReadAsync("$top=10");
        }

MainPage.xaml

<Page
    x:Class="MobileServices.MainPage"
    IsTabStop="false"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:MobileServices"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="White">

        <Grid Margin="50,50,10,10">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="*" />
            </Grid.RowDefinitions>

            <Grid Grid.Row="0" Grid.ColumnSpan="2" Margin="0,0,0,20">
                <StackPanel>
                    <ProgressBar Name="BusyProgressBar" Visibility="Collapsed" IsIndeterminate="True" />
                    <TextBlock Foreground="#0094ff" FontFamily="Segoe UI Light" Margin="0,0,0,6">WINDOWS AZURE MOBILE SERVICES</TextBlock>
                    <TextBlock Foreground="Gray" FontFamily="Segoe UI Light" FontSize="45" >Tables Viewer</TextBlock>
                    <ComboBox Name="TableSelector" ItemsSource="{Binding Newa}" SelectionChanged="TableSelector_SelectionChanged"/>
                </StackPanel>
            </Grid>

            <ScrollViewer Grid.Row="1">
                <Grid>

                    <GridView Name="ListItems" Margin="62,10,0,0" Grid.Row="1" ItemsSource="{Binding}" SelectionMode="Single">
                        <GridView.Header>
                            <GridView Name="ItemsHeader">
                                <GridView.ItemsPanel>
                                    <ItemsPanelTemplate>
                                        <StackPanel Orientation="Horizontal" HorizontalAlignment="Left" VerticalAlignment="Top"/>
                                    </ItemsPanelTemplate>
                                </GridView.ItemsPanel>
                                <GridView.ItemTemplate>
                                    <DataTemplate>
                                        <TextBlock Text="{Binding}" HorizontalAlignment="Left" VerticalAlignment="Top" Width="200" FontWeight="Bold"/>
                                    </DataTemplate>
                                </GridView.ItemTemplate>
                            </GridView>
                        </GridView.Header>
                        <GridView.ItemsPanel>
                            <ItemsPanelTemplate>
                                <StackPanel Orientation="Vertical" HorizontalAlignment="Left" VerticalAlignment="Top"/>
                            </ItemsPanelTemplate>
                        </GridView.ItemsPanel>
                        <GridView.ItemTemplate>
                            <DataTemplate>
                                <GridView Name="InnerGridView" ItemsSource="{Binding Values}" SelectionMode="None">
                                    <GridView.ItemsPanel>
                                        <ItemsPanelTemplate>
                                            <StackPanel Orientation="Horizontal" HorizontalAlignment="Left" VerticalAlignment="Top"/>
                                        </ItemsPanelTemplate>
                                    </GridView.ItemsPanel>
                                    <GridView.ItemTemplate>
                                        <DataTemplate>
                                            <TextBox Text="{Binding Value, Mode=TwoWay}" Background="{Binding ValidationError}" HorizontalAlignment="Left" VerticalAlignment="Top" Width="200" IsReadOnly="False"/>
                                        </DataTemplate>
                                    </GridView.ItemTemplate>
                                </GridView>
                            </DataTemplate>
                        </GridView.ItemTemplate>
                    </GridView>

                </Grid>
            </ScrollViewer>
        </Grid>

    </Grid>

    <Page.BottomAppBar>
        <AppBar x:Name="BottomAppBar" Padding="10,0,10,0">
            <StackPanel Orientation="Horizontal">
                <Button x:Name="BottomAppBarDelete" Tag="Delete" Style="{StaticResource DeleteAppBarButtonStyle}" HorizontalAlignment="Left" Click="DeleteClick" />
                <Button x:Name="BottomAppBarUpdate" Tag="Update" Style="{StaticResource SaveAppBarButtonStyle}" HorizontalAlignment="Left" Click="UpdateClick" />
                <Button x:Name="BottomAppBarRefresh" Tag="Refresh" Style="{StaticResource RefreshAppBarButtonStyle}" HorizontalAlignment="Left" Click="RefreshClick" />
            </StackPanel>
        </AppBar>
    </Page.BottomAppBar>
</Page>

MainPage.xaml.cs

using Microsoft.WindowsAzure.MobileServices;
using System.Linq;
using System.Threading.Tasks;
using Windows.Data.Json;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;

namespace MobileServices
{    
    public sealed partial class MainPage : Page
    {
        private MobileServiceClient adminMobileService;

        public MainPage()
        {
            this.InitializeComponent();

            this.TableSelector.ItemsSource = Constants.TableNames;
        }

        private async Task RefreshTableView()
        {
            var mobileServiceTable = GetSelectedTable();
            if (mobileServiceTable != null)
            {
                BusyProgressBar.Visibility = Windows.UI.Xaml.Visibility.Visible;

                // Get all items as json array
                var tableItems = await mobileServiceTable.ReadAsync("$top=10");

                var gridViewItems = tableItems.GetArray().Select(jsonValue => new MobileServiceTableItem(jsonValue.GetObject()));
                var gridViewItemsHeaders = tableItems.GetArray().First().GetObject().Select(o => o.Key);

                ListItems.ItemsSource = gridViewItems;
                ItemsHeader.ItemsSource = gridViewItemsHeaders;

                BusyProgressBar.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
            }
        }

        private IMobileServiceTable GetSelectedTable()
        {
            var selectedTableName = TableSelector.SelectedValue as string;
            if (selectedTableName != null)
            {
                return this.adminMobileService.GetTable(selectedTableName);
            }
            else
            {
                return null;
            }
        }

        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            base.OnNavigatedTo(e);
            string masterKey = e.Parameter as string;
            adminMobileService = App.MobileService.WithFilter(new AdminServiceFilter(true, masterKey));
            this.TableSelector.SelectedIndex = 0;
        }

        private async Task ButtonRefresh_Click(object sender, RoutedEventArgs e)
        {
            await this.RefreshTableView();
        }

        private async void TableSelector_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            await this.RefreshTableView();
        }

        private async void RefreshClick(object sender, RoutedEventArgs e)
        {
            await this.RefreshTableView();
        }

        private async void DeleteClick(object sender, RoutedEventArgs e)
        {
            var selectedTable = GetSelectedTable();
            if (selectedTable != null)
            {
                var selectedTableItem = ListItems.SelectedItem as MobileServiceTableItem;
                if (selectedTableItem != null)
                {
                    BusyProgressBar.Visibility = Windows.UI.Xaml.Visibility.Visible;

                    await selectedTable.DeleteAsync(selectedTableItem.JsonObject);
                    await this.RefreshTableView();

                    BusyProgressBar.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
                }
            }
        }

        private async void UpdateClick(object sender, RoutedEventArgs e)
        {
            var selectedTable = GetSelectedTable();
            if (selectedTable != null)
            {
                var selectedTableItem = ListItems.SelectedItem as MobileServiceTableItem;
                if (selectedTableItem != null)
                {
                    BusyProgressBar.Visibility = Windows.UI.Xaml.Visibility.Visible;

                    await selectedTable.UpdateAsync(selectedTableItem.JsonObject);
                    await this.RefreshTableView();

                    BusyProgressBar.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
                }
            }
        }
    }
}

MasterKeyInputPage.xaml

<Page
    x:Class="MobileServices.MasterKeyInputPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:MobileServices"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="White">

        <Grid Margin="50,50,10,10">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="*" />
            </Grid.RowDefinitions>

            <Grid Grid.Row="0" Grid.ColumnSpan="2" Margin="0,0,0,20">
                <StackPanel>
                    <ProgressBar Name="BusyProgressBar" Visibility="Collapsed" IsIndeterminate="True" />
                    <TextBlock Foreground="#0094ff" FontFamily="Segoe UI Light" Margin="0,0,0,6">WINDOWS AZURE MOBILE SERVICES</TextBlock>
                    <TextBlock Foreground="Gray" FontFamily="Segoe UI Light" FontSize="45" >Tables Viewer</TextBlock>
                </StackPanel>
            </Grid>

            <StackPanel Grid.Row="1" Background="{StaticResource ApplicationPageBackgroundThemeBrush}" HorizontalAlignment="Center" VerticalAlignment="Center">
                <TextBlock Text="Enter your master key" FontSize="28" HorizontalAlignment="Center" />
                <TextBox Name="MasterKeyTextBox" FontSize="24" Margin="0,30,0,30" Width="500" HorizontalAlignment="Center" />
                <Button Click="ButtonClick" HorizontalAlignment="Center" FontSize="28">Start</Button>
            </StackPanel>
        </Grid>
    </Grid>
</Page>

MasterKeyInputPage.xaml.cs

using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace MobileServices
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MasterKeyInputPage : Page
    {
        public MasterKeyInputPage()
        {
            this.InitializeComponent();
        }

        private void ButtonClick(object sender, RoutedEventArgs e)
        {
            this.Frame.Navigate(typeof(MainPage), MasterKeyTextBox.Text);
        }
    }
}

MobileServiceTableItem.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using Windows.Data.Json;
using Windows.UI;
using Windows.UI.Xaml.Media;

namespace MobileServices
{
    public class MobileServiceTableItem
    {
        public MobileServiceTableItem(JsonObject jsonObject)
        {
            this.JsonObject = jsonObject;
        }

        public JsonObject JsonObject { get; private set; }

        public IEnumerable<Item> Values
        {
            get
            {
                if (this.JsonObject != null)
                {
                    return this.JsonObject.Select(kv => new Item(kv.Key, JsonObject));
                }
                return null;
            }
        }
    }

    public class Item : INotifyPropertyChanged
    {
        public Item(string key, JsonObject jsonObject)
        {
            Key = key;
            JsonObject = jsonObject;
            ValidationError = new SolidColorBrush();
        }

        public event PropertyChangedEventHandler PropertyChanged;

        public JsonObject JsonObject { get; private set; }
        public string Key { get; private set; }

        private Brush validationError;
        public Brush ValidationError
        {
            get
            {
                return validationError;
            }
            set
            {
                validationError = value;
                OnPropertyChanged("ValidationError");
            }
        }

        public string Value
        {
            get
            {
                if (JsonObject[Key].ValueType == JsonValueType.String)
                {
                    return JsonObject[Key].GetString();
                }
                return JsonObject[Key].Stringify();
            }
            set
            {
                try
                {
                    switch (JsonObject[Key].ValueType)
                    {
                        case JsonValueType.Boolean:
                            JsonObject[Key] = JsonValue.CreateBooleanValue(bool.Parse(value));
                            break;

                        case JsonValueType.Number:
                            JsonObject[Key] = JsonValue.CreateNumberValue(double.Parse(value));
                            break;

                        case JsonValueType.String:
                            JsonObject[Key] = JsonValue.CreateStringValue(value);
                            break;

                        case JsonValueType.Null:
                        case JsonValueType.Object:
                        case JsonValueType.Array:
                        default:
                            throw new NotSupportedException("The value type is not supported: " + JsonObject[Key].ValueType);
                    }

                    ValidationError = new SolidColorBrush();
                }
                catch (FormatException)
                {
                    ValidationError = new SolidColorBrush(Colors.Red);
                }

                OnPropertyChanged("Value");
            }
        }

        protected void OnPropertyChanged(string name)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(name));
            }
        }
    }
}