src/Forms/Prism.Forms/Dialogs/DialogService.cs

@@ -49,11 +49,11 @@ namespace Prism.Dialogs
 
                 dialogAware.RequestClose = new(DialogAware_RequestClose);
 
-                async Task DialogAware_RequestClose(IDialogParameters outParameters)
+                async Task DialogAware_RequestClose(IDialogResult outResult)
                 {
                     try
                     {
-                        var result = await CloseDialogAsync(outParameters ?? new DialogParameters(), currentPage, dialogModal);
+                        var result = await CloseDialogAsync(outResult ?? new DialogResult(), currentPage, dialogModal);
                         dialogModal.RaiseDialogResult(result);
                         if (result.Exception is DialogException de && de.Message == DialogException.CanCloseIsFalse)
                         {
@@ -110,15 +110,21 @@ namespace Prism.Dialogs
             }
         }
 
-        private async System.Threading.Tasks.Task<IDialogResult> CloseDialogAsync(IDialogParameters parameters, ContentPage currentPage, DialogPage dialogModal)
+        private async System.Threading.Tasks.Task<IDialogResult> CloseDialogAsync(IDialogResult result, ContentPage currentPage, DialogPage dialogModal)
         {
             try
             {
                 PageNavigationService.NavigationSource = PageNavigationSource.DialogService;
 
-                if (parameters is null)
+                result ??= new DialogResult();
+                if (result.Parameters is null)
                 {
-                    parameters = new DialogParameters();
+                    result = new DialogResult
+                    {
+                        Exception = result.Exception,
+                        Parameters = new DialogParameters(),
+                        Result = result.Result
+                    };
                 }
 
                 var view = dialogModal.DialogView;
@@ -135,10 +141,7 @@ namespace Prism.Dialogs
                 PageUtilities.InvokeViewAndViewModelAction<IActiveAware>(currentPage, aa => aa.IsActive = true);
                 dialogAware.OnDialogClosed();
 
-                return new DialogResult
-                {
-                    Parameters = parameters
-                };
+                return result;
             }
             catch (DialogException)
             {
@@ -149,7 +152,8 @@ namespace Prism.Dialogs
                 return new DialogResult
                 {
                     Exception = ex,
-                    Parameters = parameters
+                    Parameters = result.Parameters,
+                    Result = result.Result
                 };
             }
             finally
@@ -246,7 +250,7 @@ namespace Prism.Dialogs
             }
         }
 
-        private async void InsertPopupViewInCurrentPage(ContentPage currentPage, DialogPage modalPage, View popupView, bool hideOnBackgroundTapped, DialogCloseEvent closeEvent)
+        private async void InsertPopupViewInCurrentPage(ContentPage currentPage, DialogPage modalPage, View popupView, bool hideOnBackgroundTapped, DialogCloseCallback closeEvent)
         {
             View mask = DialogLayout.GetMask(popupView);
 

src/Maui/Prism.Maui/Dialogs/DialogService.cs

@@ -14,12 +14,19 @@ public sealed class DialogService : IDialogService
     private readonly IContainerProvider _container;
     private readonly IPageAccessor _pageAccessor;
 
+    /// <summary>
+    /// Creates a new instance of the <see cref="DialogService"/> for Maui Applications
+    /// </summary>
+    /// <param name="container">The <see cref="IContainerProvider"/> that will be used to help resolve the Dialog Views.</param>
+    /// <param name="pageAccessor">The <see cref="IPageAccessor"/> used to determine where in the Navigation Stack we need to process the Dialog.</param>
+    /// <exception cref="ArgumentNullException">Throws when any constructor arguments are null.</exception>
     public DialogService(IContainerProvider container, IPageAccessor pageAccessor)
     {
         _container = container ?? throw new ArgumentNullException(nameof(container));
         _pageAccessor = pageAccessor ?? throw new ArgumentNullException(nameof(pageAccessor));
     }
 
+    /// <inheritdoc/>
     public void ShowDialog(string name, IDialogParameters parameters, DialogCallback callback)
     {
         try
@@ -35,11 +42,11 @@ public sealed class DialogService : IDialogService
             var dialogModal = _container.Resolve<IDialogContainer>();
             var dialogAware = GetDialogController(view);
 
-            async Task DialogAware_RequestClose(IDialogParameters outParameters)
+            async Task DialogAware_RequestClose(IDialogResult outResult)
             {
                 try
                 {
-                    var result = await CloseDialogAsync(outParameters ?? new DialogParameters(), currentPage, dialogModal);
+                    var result = await CloseDialogAsync(outResult ?? new DialogResult(), currentPage, dialogModal);
                     if (result.Exception is DialogException de && de.Message == DialogException.CanCloseIsFalse)
                     {
                         return;
@@ -53,7 +60,8 @@ public sealed class DialogService : IDialogService
                     var result = new DialogResult
                     {
                         Exception = dex,
-                        Parameters = parameters
+                        Parameters = parameters,
+                        Result = ButtonResult.None
                     };
 
                     if (dex.Message != DialogException.CanCloseIsFalse)
@@ -100,18 +108,28 @@ public sealed class DialogService : IDialogService
         var result = new DialogResult 
         {
             Parameters = parameters,
-            Exception = exception
+            Exception = exception,
+            Result = ButtonResult.None
         };
         await callback.Invoke(result);
     }
 
-    private static async Task<IDialogResult> CloseDialogAsync(IDialogParameters parameters, Page currentPage, IDialogContainer dialogModal)
+    private static async Task<IDialogResult> CloseDialogAsync(IDialogResult result, Page currentPage, IDialogContainer dialogModal)
     {
         try
         {
             PageNavigationService.NavigationSource = PageNavigationSource.DialogService;
 
-            parameters ??= new DialogParameters();
+            result ??= new DialogResult();
+            if (result.Parameters is null)
+            {
+                result = new DialogResult
+                {
+                    Exception = result.Exception,
+                    Parameters = new DialogParameters(),
+                    Result = result.Result
+                };
+            }
 
             var view = dialogModal.DialogView;
             var dialogAware = GetDialogController(view);
@@ -129,10 +147,7 @@ public sealed class DialogService : IDialogService
             MvvmHelpers.InvokeViewAndViewModelAction<IActiveAware>(currentPage, aa => aa.IsActive = true);
             dialogAware.OnDialogClosed();
 
-            return new DialogResult
-            {
-                Parameters = parameters
-            };
+            return result;
         }
         catch (DialogException)
         {
@@ -143,7 +158,8 @@ public sealed class DialogService : IDialogService
             return new DialogResult
             {
                 Exception = ex,
-                Parameters = parameters
+                Parameters = result.Parameters,
+                Result = result.Result
             };
         }
         finally

src/Prism.Core/Dialogs/DialogCloseEvent.cs → src/Prism.Core/Dialogs/DialogCloseCallback.cs

@@ -2,65 +2,79 @@ using System;
 using System.ComponentModel;
 using System.Threading.Tasks;
 
+#nullable enable
 namespace Prism.Dialogs;
 
 /// <summary>
-/// Provides a type to manage the invocation of a callback to close the Dialog
+/// This is set by the <see cref="IDialogService"/> on your <see cref="IDialogAware"/> ViewModel. This can then
+/// be invoked by either the DialogService or your code to initiate closing the Dialog.
 /// </summary>
-public struct DialogCloseEvent
+public struct DialogCloseCallback
 {
     private readonly MulticastDelegate _callback;
 
     /// <summary>
-    /// Creates a default instance of the <see cref="DialogCloseEvent"/>
+    /// Creates a default instance of the <see cref="DialogCloseCallback"/>
     /// </summary>
-    public DialogCloseEvent()
+    public DialogCloseCallback()
     {
-        _callback = null;
+        _callback = () => { };
     }
 
     /// <summary>
-    /// Creates an instance of the <see cref="DialogCloseEvent"/> with an <see cref="Action{IDialogParameters}"/> callback.
+    /// Creates an instance of the <see cref="DialogCloseCallback"/> with an <see cref="Action{IDialogResult}"/> callback.
     /// </summary>
     /// <param name="callback">The callback to invoke.</param>
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public DialogCloseEvent(Action<IDialogParameters> callback)
+    public DialogCloseCallback(Action<IDialogResult> callback)
     {
         _callback = callback;
     }
 
     /// <summary>
-    /// Creates an instance of the <see cref="DialogCloseEvent"/> with an <see cref="Func{IDialogParameters, Task}"/> asynchronous callback.
+    /// Creates an instance of the <see cref="DialogCloseCallback"/> with an <see cref="Func{IDialogResult, Task}"/> asynchronous callback.
     /// </summary>
     /// <param name="callback"></param>
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public DialogCloseEvent(Func<IDialogParameters, Task> callback)
+    public DialogCloseCallback(Func<IDialogResult, Task> callback)
     {
         _callback = callback;
     }
 
     /// <summary>
-    /// Invokes the initialized delegate with no <see cref="IDialogParameters"/>.
+    /// Invokes the initialized delegate with no <see cref="IDialogResult"/>.
     /// </summary>
     public void Invoke() =>
-        Invoke(null);
+        Invoke(new DialogResult());
 
     /// <summary>
     /// Invokes the initialized delegate with the specified <see cref="IDialogParameters"/>.
     /// </summary>
     /// <param name="parameters">The <see cref="IDialogParameters"/>.</param>
-    public async void Invoke(IDialogParameters parameters)
-    {
-        parameters ??= new DialogParameters();
+    /// <param name="result">The <see cref="ButtonResult"/>.</param>
+    public void Invoke(IDialogParameters parameters, ButtonResult result = ButtonResult.None) =>
+        Invoke(new DialogResult
+        {
+            Parameters = parameters,
+            Result = result
+        });
 
+    /// <summary>
+    /// Invokes the initialized delegate with the specified <see cref="IDialogResult"/>
+    /// </summary>
+    /// <param name="result"></param>
+    public async void Invoke(IDialogResult result)
+    {
         switch(_callback)
         {
-            case Action<IDialogParameters> actionCallback:
-                actionCallback(parameters);
+            case Action<IDialogResult> actionCallback:
+                actionCallback(result);
                 break;
-            case Func<IDialogParameters, Task> taskCallback:
-                await taskCallback(parameters);
+            case Func<IDialogResult, Task> taskCallback:
+                await taskCallback(result);
                 break;
+            default:
+                throw new InvalidOperationException("The DialogCloseCallback has not been properly initialized. This must be initialized by the DialogService, and should not be set by user code.");
         }
     }
 }

src/Prism.Core/Dialogs/IDialogAware.cs

@@ -23,8 +23,8 @@ public interface IDialogAware
     void OnDialogOpened(IDialogParameters parameters);
 
     /// <summary>
-    /// The <see cref="DialogCloseEvent"/> will be set by the <see cref="IDialogService"/> and can be called to
+    /// The <see cref="DialogCloseCallback"/> will be set by the <see cref="IDialogService"/> and can be called to
     /// invoke the close of the Dialog.
     /// </summary>
-    DialogCloseEvent RequestClose { get; set; }
+    DialogCloseCallback RequestClose { get; set; }
 }

src/Uno/Prism.Uno/Dialogs/DialogService.cs

@@ -58,10 +58,9 @@ namespace Prism.Dialogs
         {
             IDialogResult result = null;
 
-            Action<IDialogParameters> requestCloseHandler = null;
-            requestCloseHandler = (p) =>
+            Action<IDialogResult> requestCloseHandler = (r) =>
             {
-                result = new DialogResult { Parameters = p };
+                result = r ?? new DialogResult();
                 contentDialog.Hide();
             };
 
@@ -72,7 +71,7 @@ namespace Prism.Dialogs
 
                 if (contentDialog.DataContext is IDialogAware dialogAware)
                 {
-                    dialogAware.RequestClose = new DialogCloseEvent(requestCloseHandler);
+                    dialogAware.RequestClose = new DialogCloseCallback(requestCloseHandler);
                 }
             };
 

src/Wpf/Prism.Wpf/Dialogs/DialogService.cs

@@ -100,10 +100,9 @@ namespace Prism.Dialogs
         /// <param name="callback">The action to perform when the dialog is closed.</param>
         protected virtual void ConfigureDialogWindowEvents(IDialogWindow dialogWindow, DialogCallback callback)
         {
-            Action<IDialogParameters> requestCloseHandler = null;
-            requestCloseHandler = (p) =>
+            Action<IDialogResult> requestCloseHandler = (r) =>
             {
-                dialogWindow.Result = new DialogResult { Parameters = p };
+                dialogWindow.Result = r;
                 dialogWindow.Close();
             };
 
@@ -111,7 +110,7 @@ namespace Prism.Dialogs
             loadedHandler = (o, e) =>
             {
                 dialogWindow.Loaded -= loadedHandler;
-                dialogWindow.GetDialogViewModel().RequestClose = new DialogCloseEvent(requestCloseHandler);
+                dialogWindow.GetDialogViewModel().RequestClose = new DialogCloseCallback(requestCloseHandler);
             };
             dialogWindow.Loaded += loadedHandler;
 

tests/Forms/Prism.Forms.Tests/Services/Mocks/Dialogs/DialogMockViewModel.cs

-using System;
-using Prism.AppModel;
+using Prism.Dialogs;
 using Prism.Mvvm;
-using Prism.Dialogs;
 
 namespace Prism.Forms.Tests.Services.Mocks.Dialogs
 {
@@ -14,7 +12,7 @@ namespace Prism.Forms.Tests.Services.Mocks.Dialogs
             set => SetProperty(ref _title, value);
         }
 
-        public DialogCloseEvent RequestClose { get; set; }
+        public DialogCloseCallback RequestClose { get; set; }
 
         public bool CanClose { get; set; } = true;