feat: implement default button for dialog control.

demo/Ursa.Demo/Dialogs/DialogWithActionViewModel.cs

@@ -12,7 +12,7 @@ public partial class DialogWithActionViewModel: ObservableObject, IDialogContext
     [ObservableProperty] private string _title;
     [ObservableProperty] private DateTime _date;
     public object? DefaultCloseResult { get; set; } = true;
-    public event EventHandler<object>? Closed;
+    public event EventHandler<object?>? Closed;
     
     public ICommand OKCommand { get; set; }
     public ICommand CancelCommand { get; set; }

demo/Ursa.Demo/Dialogs/PlainDialog.axaml

@@ -4,5 +4,8 @@
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
              mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
              x:Class="Ursa.Demo.Dialogs.PlainDialog">
-    
+    <StackPanel Margin="8">
+        <TextBlock Classes="Strong" Margin="8"  Text="{Binding Title}"></TextBlock>
+        <Calendar SelectedDate="{Binding Date}" ></Calendar>
+    </StackPanel>
 </UserControl>

demo/Ursa.Demo/Pages/DialogDemo.axaml

@@ -25,6 +25,7 @@
             <Button Command="{Binding ShowLocalOverlayModalDialogCommand}">Show Local Overlay Modal Dialog</Button>
             <Button Command="{Binding ShowGlobalOverlayModalDialogCommand}"> Show Global Overlay Modal Dialog </Button>
             <Button Command="{Binding ShowGlobalOverlayDialogCommand}">Show Global Overlay Dialog</Button>
+            <Button Command="{Binding ShowPlainGlobalOverlayDialogCommand}">Default Buttons</Button>
         </StackPanel>
         <Grid Grid.Column="1">
             <Button

demo/Ursa.Demo/ViewModels/DialogDemoViewModel.cs

@@ -3,6 +3,7 @@ using System.Threading.Tasks;
 using System.Windows.Input;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
+using Ursa.Common;
 using Ursa.Controls;
 using Ursa.Demo.Dialogs;
 using Ursa.Demo.Pages;
@@ -16,6 +17,8 @@ public class DialogDemoViewModel: ObservableObject
     public ICommand ShowGlobalModalDialogCommand { get; }
     
     public ICommand ShowGlobalOverlayDialogCommand { get; }
+    
+    public ICommand ShowPlainGlobalOverlayDialogCommand { get; }
 
     private object? _result;
 
@@ -41,6 +44,7 @@ public class DialogDemoViewModel: ObservableObject
         ShowGlobalOverlayModalDialogCommand = new AsyncRelayCommand(ShowGlobalOverlayModalDialog);
         ShowGlobalModalDialogCommand = new AsyncRelayCommand(ShowGlobalModalDialog);
         ShowGlobalOverlayDialogCommand = new RelayCommand(ShowGlobalOverlayDialog);
+        ShowPlainGlobalOverlayDialogCommand = new AsyncRelayCommand(ShowPlainGlobalOverlayDialog);
     }
 
     private void ShowGlobalOverlayDialog()
@@ -63,7 +67,18 @@ public class DialogDemoViewModel: ObservableObject
     {
         var vm = new DialogWithActionViewModel();
         var result = await OverlayDialog.ShowModalAsync<DialogWithAction, DialogWithActionViewModel, bool>(
-            DialogViewModel, new DialogOptions() { ExtendToClientArea = true }, "LocalHost");
+            DialogViewModel, new DialogOptions() { ExtendToClientArea = true}, "LocalHost");
         Result = result;
     }
+    
+    public async Task ShowPlainGlobalOverlayDialog()
+    {
+        var result = await OverlayDialog.ShowModalAsync<PlainDialog, PlainDialogViewModel, object?>(
+            new PlainDialogViewModel(),
+            new DialogOptions()
+            {
+                DefaultButtons = DialogButton.OKCancel,
+            }, 
+            "LocalHost");
+    }
 }