关于C#中泛型类型参数约束（whereT:class）

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如下在WPF中获取当前窗体（或者用户控件）的父窗体，限定泛型必须为Class:

private void btnCancel_Click(object sender, RoutedEventArgs e)
        {
            Window hostWindow = GetParent<Window>(sender as Button);
            if (hostWindow != null)
            {
                hostWindow.Close();
            }
        }

        public static T GetParent<T>(UIElement  uiElement) where T : class
        {
            T result;
            var dp = LogicalTreeHelper.GetParent(uiElement);
            result = dp as T;
            while (result == null)
            {
                dp = LogicalTreeHelper.GetParent(dp);
                result = dp as T;
                if (dp == null) return null;
            }
            return result;
        }

如下在WPF中获取当前窗体（或者用户控件）的父窗体，限定泛型必须为Class:

private void btnCancel_Click(object sender, RoutedEventArgs e)
        {
            Window hostWindow = GetParent<Window>(sender as Button);
            if (hostWindow != null)
            {
                hostWindow.Close();
            }
        }

        public static T GetParent<T>(UIElement  uiElement) where T : class
        {
            T result;
            var dp = LogicalTreeHelper.GetParent(uiElement);
            result = dp as T;
            while (result == null)
            {
                dp = LogicalTreeHelper.GetParent(dp);
                result = dp as T;
                if (dp == null) return null;
            }
            return result;
        }