优化更新代码，添加界面功能并整合

WPFluent/Controls/ContentDialog/ContentDialogButton.cs

@@ -0,0 +1,28 @@
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file, You can obtain one at https://opensource.org/licenses/MIT.
+// Copyright (C) Leszek Pomianowski and WPF UI Contributors.
+// All Rights Reserved.
+
+// ReSharper disable once CheckNamespace
+namespace WPFluent.Controls;
+
+/// <summary>
+/// Defines constants that specify the default button on a <see cref="ContentDialog"/>.
+/// </summary>
+public enum ContentDialogButton
+{
+    /// <summary>
+    /// The primary button is the default.
+    /// </summary>
+    Primary,
+
+    /// <summary>
+    /// The secondary button is the default.
+    /// </summary>
+    Secondary,
+
+    /// <summary>
+    /// The close button is the default.
+    /// </summary>
+    Close,
+}