add mechanism for easy access of a dialog from a view model

MahApps.Metro/Controls/Dialogs/DialogCoordinator.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Threading.Tasks;
+using System.Windows;
+
+namespace MahApps.Metro.Controls.Dialogs
+{
+    public class DialogCoordinator : IDialogCoordinator
+    {
+        /// <summary>
+        /// Gets the default instance if the dialog coordinator, which can be injected into a view model.
+        /// </summary>
+        public static readonly DialogCoordinator Instance = new DialogCoordinator();
+
+        public Task<string> ShowInputAsync(object context, string title, string message, MetroDialogSettings metroDialogSettings = null)
+        {            
+            var metroWindow = GetMetroWindow(context);
+
+            return metroWindow.ShowInputAsync(title, message, metroDialogSettings);
+        }
+
+        public Task<LoginDialogData> ShowLoginAsync(object context, string title, string message, MessageDialogStyle style = MessageDialogStyle.Affirmative, LoginDialogSettings settings = null)
+        {
+            var metroWindow = GetMetroWindow(context);
+
+            return metroWindow.ShowLoginAsync(title, message, settings);
+        }
+
+        public Task<MessageDialogResult> ShowMessageAsync(object context, string title, string message, MessageDialogStyle style = MessageDialogStyle.Affirmative, MetroDialogSettings settings = null)
+        {
+            var metroWindow = GetMetroWindow(context);
+
+            return metroWindow.ShowMessageAsync(title, message, style, settings);
+        }
+
+        public Task<ProgressDialogController> ShowProgressAsync(object context, string title, string message,
+            bool isCancelable = false, MetroDialogSettings settings = null)
+        {
+            var metroWindow = GetMetroWindow(context);
+
+            return metroWindow.ShowProgressAsync(title, message, isCancelable, settings);
+        }
+
+        public Task ShowMetroDialogAsync(object context, BaseMetroDialog dialog,
+            MetroDialogSettings settings = null)
+        {
+            var metroWindow = GetMetroWindow(context);
+
+            return metroWindow.ShowMetroDialogAsync(dialog, settings);
+        }
+
+        public Task HideMetroDialogAsync(object context, BaseMetroDialog dialog, MetroDialogSettings settings = null)
+        {
+            var metroWindow = GetMetroWindow(context);
+
+            return metroWindow.HideMetroDialogAsync(dialog, settings);
+        }
+
+        public Task<TDialog> GetCurrentDialogAsync<TDialog>(object context) where TDialog : BaseMetroDialog
+        {
+            var metroWindow = GetMetroWindow(context);
+
+            return metroWindow.GetCurrentDialogAsync<TDialog>();
+        }
+
+        private static MetroWindow GetMetroWindow(object context)
+        {
+            if (context == null) throw new ArgumentNullException("context");
+            if (!DialogParticipation.IsRegistered(context))
+                throw new InvalidOperationException(
+                    "Context is not registered. Consider using DialogParticipation.Register in XAML to bind in the DataContext.");
+
+            var association = DialogParticipation.GetAssociation(context);
+            var metroWindow = Window.GetWindow(association) as MetroWindow;
+
+            if (metroWindow == null)
+                throw new InvalidOperationException("Control is not inside a MetroWindow.");
+            return metroWindow;
+        }
+    }
+}

MahApps.Metro/Controls/Dialogs/DialogParticipation.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Windows;
+
+namespace MahApps.Metro.Controls.Dialogs
+{
+    public static class DialogParticipation
+    {
+        private static readonly IDictionary<object, DependencyObject> ContextRegistrationIndex = new Dictionary<object, DependencyObject>();
+
+        public static readonly DependencyProperty RegisterProperty = DependencyProperty.RegisterAttached(
+            "Register", typeof(object), typeof(DialogParticipation), new PropertyMetadata(default(object), RegisterPropertyChangedCallback));
+
+        private static void RegisterPropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
+        {
+            if (dependencyPropertyChangedEventArgs.OldValue != null)
+                ContextRegistrationIndex.Remove(dependencyPropertyChangedEventArgs.OldValue);
+
+            if (dependencyPropertyChangedEventArgs.NewValue != null)
+                ContextRegistrationIndex[dependencyPropertyChangedEventArgs.NewValue] = dependencyObject;
+        }
+
+        public static void SetRegister(DependencyObject element, object context)
+        {
+            element.SetValue(RegisterProperty, context);
+        }
+
+        public static object GetRegister(DependencyObject element)
+        {
+            return element.GetValue(RegisterProperty);
+        }
+
+        internal static bool IsRegistered(object context)
+        {
+            if (context == null) throw new ArgumentNullException("context");
+
+            return ContextRegistrationIndex.ContainsKey(context);
+        }
+
+        internal static DependencyObject GetAssociation(object context)
+        {
+            if (context == null) throw new ArgumentNullException("context");
+
+            return ContextRegistrationIndex[context];
+        }
+    }
+}

MahApps.Metro/Controls/Dialogs/IDialogCoordinator.cs

@@ -0,0 +1,86 @@
+using System;
+using System.Threading.Tasks;
+
+namespace MahApps.Metro.Controls.Dialogs
+{
+    /// <summary>
+    /// Use the dialog coordinator to help you interfact with dialogs from a view model.
+    /// </summary>
+    public interface IDialogCoordinator
+    {
+        /// <summary>
+        /// Shows the input dialog.
+        /// </summary>
+        /// <param name="context">Typically this should be the view model, which you register in XAML using <see cref="DialogParticipation.SetRegister"/>.</param>
+        /// <param name="title">The title of the MessageDialog.</param>
+        /// <param name="message">The message contained within the MessageDialog.</param>
+        /// <param name="settings">Optional settings that override the global metro dialog settings.</param>
+        /// <returns>The text that was entered or null (Nothing in Visual Basic) if the user cancelled the operation.</returns>
+        Task<string> ShowInputAsync(object context, string title, string message, MetroDialogSettings settings = null);
+
+        /// <summary>
+        /// Creates a LoginDialog inside of the current window.
+        /// </summary>
+        /// <param name="context">Typically this should be the view model, which you register in XAML using <see cref="DialogParticipation.SetRegister"/>.</param>
+        /// <param name="title">The title of the LoginDialog.</param>
+        /// <param name="message">The message contained within the LoginDialog.</param>
+        /// <param name="style"></param>
+        /// <param name="settings">Optional settings that override the global metro dialog settings.</param>
+        /// <returns>The text that was entered or null (Nothing in Visual Basic) if the user cancelled the operation.</returns>
+        Task<LoginDialogData> ShowLoginAsync(object context, string title, string message, MessageDialogStyle style = MessageDialogStyle.Affirmative, LoginDialogSettings settings = null);
+
+        /// <summary>
+        /// Creates a MessageDialog inside of the current window.
+        /// </summary>
+        /// <param name="context">Typically this should be the view model, which you register in XAML using <see cref="DialogParticipation.SetRegister"/>.</param>
+        /// <param name="title">The title of the MessageDialog.</param>
+        /// <param name="message">The message contained within the MessageDialog.</param>
+        /// <param name="style">The type of buttons to use.</param>
+        /// <param name="settings">Optional settings that override the global metro dialog settings.</param>
+        /// <returns>A task promising the result of which button was pressed.</returns>
+        Task<MessageDialogResult> ShowMessageAsync(object context, string title, string message, MessageDialogStyle style = MessageDialogStyle.Affirmative, MetroDialogSettings settings = null);
+
+        /// <summary>
+        /// Creates a ProgressDialog inside of the current window.
+        /// </summary>
+        /// <param name="context">Typically this should be the view model, which you register in XAML using <see cref="DialogParticipation.SetRegister"/>.</param>
+        /// <param name="title">The title of the ProgressDialog.</param>
+        /// <param name="message">The message within the ProgressDialog.</param>
+        /// <param name="isCancelable">Determines if the cancel button is visible.</param>
+        /// <param name="settings">Optional Settings that override the global metro dialog settings.</param>
+        /// <returns>A task promising the instance of ProgressDialogController for this operation.</returns>
+        Task<ProgressDialogController> ShowProgressAsync(object context, string title, string message,
+            bool isCancelable = false, MetroDialogSettings settings = null);
+
+        /// <summary>
+        /// Adds a Metro Dialog instance to the specified window and makes it visible asynchronously.        
+        /// <para>You have to close the resulting dialog yourself with <see cref="HideMetroDialogAsync"/>.</para>
+        /// </summary>
+        /// <param name="context">Typically this should be the view model, which you register in XAML using <see cref="DialogParticipation.SetRegister"/>.</param>
+        /// <param name="dialog">The dialog instance itself.</param>
+        /// <param name="settings">An optional pre-defined settings instance.</param>
+        /// <returns>A task representing the operation.</returns>
+        /// <exception cref="InvalidOperationException">The <paramref name="dialog"/> is already visible in the window.</exception>
+        Task ShowMetroDialogAsync(object context, BaseMetroDialog dialog,
+            MetroDialogSettings settings = null);
+
+        /// <summary>
+        /// Hides a visible Metro Dialog instance.
+        /// </summary>
+        /// <param name="context">Typically this should be the view model, which you register in XAML using <see cref="DialogParticipation.SetRegister"/>.</param>
+        /// <param name="dialog">The dialog instance to hide.</param>
+        /// <param name="settings">An optional pre-defined settings instance.</param>
+        /// <returns>A task representing the operation.</returns>
+        /// <exception cref="InvalidOperationException">
+        /// The <paramref name="dialog"/> is not visible in the window.
+        /// This happens if <see cref="ShowMetroDialogAsync"/> hasn't been called before.
+        /// </exception>
+        Task HideMetroDialogAsync(object context, BaseMetroDialog dialog, MetroDialogSettings settings = null);
+
+        /// <summary>
+        /// Gets the current shown dialog.
+        /// </summary>
+        /// <param name="context">Typically this should be the view model, which you register in XAML using <see cref="DialogParticipation.SetRegister"/>.</param>
+        Task<TDialog> GetCurrentDialogAsync<TDialog>(object context) where TDialog : BaseMetroDialog;        
+    }
+}

MahApps.Metro/MahApps.Metro.NET45.csproj

@@ -130,6 +130,9 @@
     <Compile Include="Behaviours\StylizedBehaviorCollection.cs" />
     <Compile Include="Behaviours\TabControlSelectFirstVisibleTabBehavior.cs" />
     <Compile Include="Behaviours\WindowsSettingBehaviour.cs" />
+    <Compile Include="Controls\Dialogs\DialogCoordinator.cs" />
+    <Compile Include="Controls\Dialogs\DialogParticipation.cs" />
+    <Compile Include="Controls\Dialogs\IDialogCoordinator.cs" />
     <Compile Include="Controls\Helper\ButtonHelper.cs" />
     <Compile Include="Controls\ClosingWindowEventHandlerArgs.cs" />
     <Compile Include="Controls\Helper\ComboBoxHelper.cs" />

MahApps.Metro/MahApps.Metro.csproj

@@ -85,6 +85,8 @@
     <Compile Include="Actions\SetFlyoutOpenAction.cs" />
     <Compile Include="Behaviours\BindableResourceBehavior.cs" />
     <Compile Include="Behaviours\BorderlessWindowBehavior.cs" />
+    <Compile Include="Controls\Dialogs\DialogCoordinator.cs" />
+    <Compile Include="Controls\Dialogs\DialogParticipation.cs" />
     <Compile Include="Behaviours\GlowWindowBehavior.cs" />
     <Compile Include="Behaviours\PasswordBoxBindingBehavior.cs" />
     <Compile Include="Behaviours\StylizedBehaviorCollection.cs" />
@@ -95,6 +97,7 @@
     <Compile Include="Controls\Dialogs\BaseMetroDialog.cs" />
     <Compile Include="Controls\Dialogs\DialogManager.cs" />
     <Compile Include="Controls\Dialogs\DialogStateChangedEventArgs.cs" />
+    <Compile Include="Controls\Dialogs\IDialogCoordinator.cs" />
     <Compile Include="Controls\Dialogs\InputDialog.cs" />
     <Compile Include="Controls\Dialogs\LoginDialog.cs" />
     <Compile Include="Controls\Dialogs\ProgressDialog.cs" />

samples/MetroDemo/ExampleWindows/FlyoutDemo.xaml.cs

@@ -2,6 +2,7 @@
 using System.Windows;
 using System.Windows.Input;
 using MahApps.Metro.Controls;
+using MahApps.Metro.Controls.Dialogs;
 using MetroDemo.Models;
 
 namespace MetroDemo.ExampleWindows
@@ -13,7 +14,7 @@ public partial class FlyoutDemo : IDisposable
 
         public FlyoutDemo()
         {
-            this.DataContext = new MainWindowViewModel();
+            this.DataContext = new MainWindowViewModel(DialogCoordinator.Instance);
             this.InitializeComponent();
             this.Closing += (s, e) =>
                 {

samples/MetroDemo/MainWindow.xaml

@@ -20,7 +20,9 @@
                       d:DesignHeight="600"
                       d:DesignWidth="800"
                       d:DataContext="{d:DesignInstance MetroDemo:MainWindowViewModel}"
-                      Closing="MetroWindow_Closing">
+                      Closing="MetroWindow_Closing"
+                      Dialog:DialogParticipation.Register="{Binding}"
+                      >
 
     <Window.Resources>
         <ResourceDictionary>
@@ -178,6 +180,17 @@
                               Header="Show CustomDialog Externally" />
                     <MenuItem Click="ShowAwaitCustomDialog"
                               Header="Await CustomDialog" />
+                    <Separator />
+                    <MenuItem Command="{Binding ShowInputDialogCommand}"
+                              Header="Show InputDialog via VM" />
+                    <MenuItem Command="{Binding ShowLoginDialogCommand}"
+                              Header="Show LoginDialog via VM" />
+                    <MenuItem Command="{Binding ShowMessageDialogCommand}"
+                              Header="Show MessageDialog via VM" />
+                    <MenuItem Command="{Binding ShowProgressDialogCommand}"
+                              Header="Show ProgressDialog via VM" />
+                    <MenuItem Command="{Binding ShowCustomDialogCommand}"
+                              Header="Show CustomDialog via VM" />
                 </MenuItem>
                 <MenuItem Header="Window">
                     <MenuItem IsCheckable="True" Header="ShowInTaskbar"

samples/MetroDemo/MainWindow.xaml.cs

@@ -17,7 +17,7 @@ public partial class MainWindow
 
         public MainWindow()
         {
-            _viewModel = new MainWindowViewModel();
+            _viewModel = new MainWindowViewModel(DialogCoordinator.Instance);
             DataContext = _viewModel;
 
             InitializeComponent();