feat: fix MessageBox default position, use internal option default instance.

src/Ursa/Controls/Dialog/Dialog.cs

@@ -217,10 +217,7 @@ public static class Dialog
     /// <param name="options"></param>
     private static void ConfigureDefaultDialogWindow(DefaultDialogWindow window, DialogOptions? options)
     {
-        if (options is null)
+        options ??= DialogOptions.Default;
-        {
-            options = new DialogOptions();
-        }
         window.WindowStartupLocation = options.StartupLocation;
         window.Title = options.Title;
         window.Buttons = options.Button;

src/Ursa/Controls/Dialog/DialogControl.cs

@@ -22,8 +22,8 @@ public class DialogControl: ContentControl
     protected internal Button? _closeButton;
     private Panel? _titleArea;
 
-    internal HorizontalPosition HorizontalAnchor { get; set; }
+    internal HorizontalPosition HorizontalAnchor { get; set; } = HorizontalPosition.Center;
-    internal VerticalPosition VerticalAnchor { get; set; }
+    internal VerticalPosition VerticalAnchor { get; set; } = VerticalPosition.Center;
     internal HorizontalPosition ActualHorizontalAnchor { get; set; }
     internal VerticalPosition ActualVerticalAnchor { get; set; }
     internal double? HorizontalOffset { get; set; }

src/Ursa/Controls/Dialog/Options/DialogOptions.cs

@@ -5,7 +5,7 @@ namespace Ursa.Controls;
 
 public class DialogOptions
 {
-    public static DialogOptions Default { get; } = new DialogOptions();
+    internal static DialogOptions Default { get; } = new DialogOptions();
     /// <summary>
     /// The Startup Location of DialogWindow. Default is <see cref="WindowStartupLocation.CenterOwner"/>
     /// </summary>

src/Ursa/Controls/Dialog/Options/OverlayDialogOptions.cs

@@ -16,6 +16,7 @@ public enum VerticalPosition
 
 public class OverlayDialogOptions
 {
+    internal static OverlayDialogOptions Default { get; } = new OverlayDialogOptions();
     public bool CanClickOnMaskToClose { get; set; } = false;
     public HorizontalPosition HorizontalAnchor { get; set; } = HorizontalPosition.Center;
     public VerticalPosition VerticalAnchor { get; set; } = VerticalPosition.Center;

src/Ursa/Controls/Dialog/OverlayDialog.cs

@@ -180,7 +180,7 @@ public static class OverlayDialog
     
     private static void ConfigureDialogControl(DialogControl control, OverlayDialogOptions? options)
     {
-        if (options is null) options = new OverlayDialogOptions();
+        options ??= OverlayDialogOptions.Default;
         control.HorizontalAnchor = options.HorizontalAnchor;
         control.VerticalAnchor = options.VerticalAnchor;
         control.ActualHorizontalAnchor = options.HorizontalAnchor;

src/Ursa/Controls/MessageBox/MessageBoxControl.cs

@@ -132,4 +132,17 @@ public class MessageBoxControl: DialogControl
     {
         if (button is not null) button.IsVisible = visible;
     }
+
+    internal override void CloseDialog()
+    {
+        MessageBoxResult result = Buttons switch
+        {
+            MessageBoxButton.OK => MessageBoxResult.OK,
+            MessageBoxButton.OKCancel => MessageBoxResult.Cancel,
+            MessageBoxButton.YesNo => MessageBoxResult.No,
+            MessageBoxButton.YesNoCancel => MessageBoxResult.Cancel,
+            _ => MessageBoxResult.None
+        };
+        OnDialogControlClosing(this, result);
+    }
 }