雪花控件类：

class MM:Control

    {

        DispatcherTimer dispatcherTimer = new DispatcherTimer();

        public MM()

        {

            dispatcherTimer.Interval = TimeSpan.FromMilliseconds(100); ;

            dispatcherTimer.Tick += DispatcherTimer_Tick;

            dispatcherTimer.Start();

        }

        private void DispatcherTimer_Tick(object sender, EventArgs e)

        {

            this.InvalidateVisual();

        }

        protected override void OnRender(DrawingContext drawingContext)

        {

            var currentcolor = Colors.White;

            Brush brush = new RadialGradientBrush(currentcolor,

                    Color.FromArgb(0, currentcolor.R, currentcolor.G, currentcolor.B));

            Random r = new Random();

            for (int i = 0; i < 530; i++)

            {

                var w = 35 * r.NextDouble();

                var rect =

                new RectangleGeometry(

                    new Rect(new Point(r.Next(10,(int)this.Width), r.Next(10, (int)this.Height)),

                        new Size(w, w)));

                drawingContext.DrawGeometry(brush, null, rect);

            }

        }

    }

前台代码：

<Window x:Class="WpfAppTest.MainWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

        xmlns:local="clr-namespace:WpfAppTest"

        mc:Ignorable="d"  WindowStyle="None" AllowsTransparency="True" Top="100" Left="100"

        Title="MainWindow" Height="450" Width="800">

    <Window.Background>

        <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">

            <GradientStop Color="#05438C" Offset="0"/>

            <GradientStop Color="White" Offset="0.9"/>

            <GradientStop Color="White" Offset="1"/>

        </LinearGradientBrush>

    </Window.Background>

    <local:MM x:Name="cc" HorizontalAlignment="Left" Height="417.114"  VerticalAlignment="Top" Width="791.112" RenderTransformOrigin="0.5,0.5" Margin="0,0.007,0,0">

        <local:MM.RenderTransform>

            <TransformGroup>

                <ScaleTransform/>

                <SkewTransform/>

                <RotateTransform Angle="0.387"/>

                <TranslateTransform/>

            </TransformGroup>

        </local:MM.RenderTransform>

    </local:MM>

</Window>