在很早之前，我曾经写过一个GDI+的时钟，见“C#时钟控件 （C# Clock Control）” http://blog.csdn.net/johnsuna/archive/2006/02/13/597746.aspx及“使用C#编写LED样式时钟控件”（http://blog.csdn.net/johnsuna/archive/2006/02/14/598867.aspx），进入WPF时代了，如何用WPF绘制一个时钟呢？

先看效果：

上面显示的是时间值，下面是图形版的时钟。

制作要点：
1. 首先在Expression Blend中画出时钟的样式;
2. 建立时钟的程序辅助类;
3. 将此时钟样式需要动态换掉的部分改成相应的绑定值。

由于具体步骤很多，这里只说说技术难点和要点，着重说明上述第2点部分。
// 时钟控件类：Clock.cs
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using System.Timers;
using System.Windows.Threading;

namespace BrawDraw.Com.WPF.Clock.ControlLibrary
{
    /// <summary>Clock Control
 /// </summary>

 public class Clock : Control
 {
  private DispatcherTimer timer;

  static Clock()
  {
   DefaultStyleKeyProperty.OverrideMetadata(typeof(Clock), new FrameworkPropertyMetadata(typeof(Clock)));
  }

  protected override void OnInitialized(EventArgs e)
  {
   base.OnInitialized(e);
   timer = new DispatcherTimer();
   timer.Tick += new EventHandler(Timer_Tick);
   timer.Start();
  }

  private void Timer_Tick(object sender, EventArgs e)
  {
   UpdateDateTime();
   timer.Interval = TimeSpan.FromMilliseconds(1000 - DateTime.Now.Millisecond);
  }

  private void UpdateDateTime()
  {
   this.DateTime = System.DateTime.Now;
  }

  #region DateTime property
  public DateTime DateTime
  {
   get
   {
    return (DateTime)GetValue(DateTimeProperty);
   }
   private set
   {
    SetValue(DateTimeProperty, value);
   }
  }

  public static DependencyProperty DateTimeProperty = DependencyProperty.Register(
    "DateTime",
    typeof(DateTime),
    typeof(Clock),
    new PropertyMetadata(DateTime.Now, new PropertyChangedCallback(OnDateTimeInvalidated)));

  public static readonly RoutedEvent DateTimeChangedEvent =
   EventManager.RegisterRoutedEvent("DateTimeChanged", RoutingStrategy.Bubble, typeof(RoutedPropertyChangedEventHandler<DateTime>), typeof(Clock));

  protected virtual void OnDateTimeChanged(DateTime oldValue, DateTime newValue)
  {
   RoutedPropertyChangedEventArgs<DateTime> args = new RoutedPropertyChangedEventArgs<DateTime>(oldValue, newValue);
   args.RoutedEvent = Clock.DateTimeChangedEvent;
   RaiseEvent(args);
  }

  private static void OnDateTimeInvalidated(DependencyObject d, DependencyPropertyChangedEventArgs e)
  {
   Clock clock = (Clock)d;

   DateTime oldValue = (DateTime)e.OldValue;
   DateTime newValue = (DateTime)e.NewValue;

   clock.OnDateTimeChanged(oldValue, newValue);
  }
  #endregion
 }
}

// 时钟内部时针、分针、秒针角度计算及星期显示的类： ClockConverters.cs
// 由于WPF中旋转角度是以度单位，计算为绕一个圆周时，为360度。所以，计算时以360度来计算。
using System;
using System.Globalization;
using System.Windows.Data;

namespace BrawDraw.Com.WPF.Clock
{
    // 一分钟60秒，一周为360度，所以，一秒钟就占6度，所以是：秒数×6。
    [ValueConversion(typeof(DateTime), typeof(int))]
    public class SecondsConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            DateTime date = (DateTime)value;
            return date.Second * 6;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return null;
        }
    }

// 一小时是60分钟，一周为360度，所以，一分钟就占6度，所以是：分钟数×6。
    [ValueConversion(typeof(DateTime), typeof(int))]
    public class MinutesConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            DateTime date = (DateTime)value;
            return date.Minute * 6;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return null;
        }
    }

// 时钟上显示12小时，一周为360度，这样，每小时占30度，考虑分钟所占角度是分钟数/2，所以结果是：小时数×30 + 分钟数/2。
    [ValueConversion(typeof(DateTime), typeof(int))]
    public class HoursConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            DateTime date = (DateTime)value;
            return (date.Hour * 30) + (date.Minute / 2);
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return null;
        }
    }

    [ValueConversion(typeof(DateTime), typeof(string))]
    public class WeekdayConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            DateTime date = (DateTime)value;
            return date.DayOfWeek.ToString().Substring(0,3);
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return null;
        }
    }
}

剩下的就十分简单，程序的显示部分(XAML代码)：
// MainWindow.xaml
<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 xmlns:customControl="clr-namespace:BrawDraw.Com.WPF.Clock.ControlLibrary;assembly=CustomControlLibrary"
 xmlns:local="clr-namespace:BrawDraw.Com.WPF.Clock"
    x:Class="BrawDraw.Com.WPF.Clock.Window1"
    Title="WPF Clock" Height="394" Width="332"
    >
 <StackPanel HorizontalAlignment="Center">
  <StackPanel.Resources>
   <local:SecondsConverter x:Key="secondsConverter"/>
   <local:MinutesConverter x:Key="minutesConverter"/>
   <local:HoursConverter x:Key="hoursConverter"/>
   <local:WeekdayConverter x:Key="weekdayConverter"/>
   <Style x:Key="AnalogClock" TargetType="{x:Type customControl:Clock}">
    <Setter Property="Template">
     <Setter.Value>
      <ControlTemplate TargetType="{x:Type customControl:Clock}">
       <Grid>
        <Grid.ColumnDefinitions>
         <ColumnDefinition Width="108" />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
         <RowDefinition Height="108" />
        </Grid.RowDefinitions>
        <Ellipse Width="108" Height="108" StrokeThickness="3" Grid.Row="0" Grid.Column="0">
         <Ellipse.Stroke>
          <LinearGradientBrush>
           <LinearGradientBrush.GradientStops>
            <GradientStop Color="LightBlue" Offset="0" />
            <GradientStop Color="DarkBlue" Offset="1" />
           </LinearGradientBrush.GradientStops>
          </LinearGradientBrush>
         </Ellipse.Stroke>
        </Ellipse>
        <Ellipse VerticalAlignment="Center" HorizontalAlignment="Center" Width="104" Height="104" StrokeThickness="3">
         <Ellipse.Stroke>
          <LinearGradientBrush>
           <LinearGradientBrush.GradientStops>
            <GradientStop Color="DarkBlue" Offset="0" />
            <GradientStop Color="LightBlue" Offset="1" />
           </LinearGradientBrush.GradientStops>
          </LinearGradientBrush>
         </Ellipse.Stroke>
         <Ellipse.Fill>
          <LinearGradientBrush EndPoint="0.96,0.972" StartPoint="0.017,0.03">
           <GradientStop Color="#FFFAF9F6" Offset="0"/>
           <GradientStop Color="#FF539BDF" Offset="1"/>
          </LinearGradientBrush>
         </Ellipse.Fill>
        </Ellipse>

        <TextBlock HorizontalAlignment="Center" Margin="0,0,0,30"  VerticalAlignment="Bottom" FontSize="10" Name="MonthDay" Text="{Binding Path=DateTime, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource weekdayConverter}}"/>

<!-- 下面这一部分有待改进，使用C#代码控制起来会更方便，且更有利于代码的维护 -->
        <Canvas Width="102" Height="102">
         <Ellipse Width="8" Height="8" Fill="Black" Canvas.Top="46" Canvas.Left="46" />
         <Rectangle Canvas.Top="5" Canvas.Left="48" Fill="Black" Width="4" Height="8">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="0" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="49" Fill="Black" Width="2" Height="6">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="30" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="49" Fill="Black" Width="2" Height="6">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="60" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="48" Fill="Black" Width="4" Height="8">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="90" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="49" Fill="Black" Width="2" Height="6">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="120" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="49" Fill="Black" Width="2" Height="6">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="150" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="48" Fill="Black" Width="4" Height="8">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="180" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="49" Fill="Black" Width="2" Height="6">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="210" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="49" Fill="Black" Width="2" Height="6">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="240" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="48" Fill="Black" Width="4" Height="8">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="270" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="49" Fill="Black" Width="2" Height="6">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="300" />
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle Canvas.Top="5" Canvas.Left="49" Fill="Black" Width="2" Height="6">
          <Rectangle.RenderTransform>
           <RotateTransform CenterX="2" CenterY="46" Angle="330" />
          </Rectangle.RenderTransform>
         </Rectangle>

<!-- 时钟、分针和秒针的显示 -->
         <Rectangle x:Name="HourHand" Canvas.Top="21" Canvas.Left="48"
            Fill="Black" Width="4" Height="30">
          <Rectangle.RenderTransform>
           <RotateTransform Angle="{Binding Path=DateTime, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource hoursConverter}}" CenterX="2" CenterY="30"></RotateTransform>
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle x:Name="MinuteHand" Canvas.Top="10" Canvas.Left="51"
           Fill="DarkOrange" Width="2" Height="40">
          <Rectangle.RenderTransform>
           <RotateTransform Angle="{Binding Path=DateTime, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource minutesConverter}}" CenterX="1" CenterY="40"></RotateTransform>
          </Rectangle.RenderTransform>
         </Rectangle>
         <Rectangle x:Name="SecondHand" Canvas.Top="4" Canvas.Left="49"
           Fill="Red" Width="1" Height="47">
          <Rectangle.RenderTransform>
           <RotateTransform Angle="{Binding Path=DateTime, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource secondsConverter}}" CenterX="0.5" CenterY="47"></RotateTransform>
          </Rectangle.RenderTransform>
         </Rectangle>
        </Canvas>
       </Grid>
      </ControlTemplate>
     </Setter.Value>
    </Setter>
   </Style>
  </StackPanel.Resources>
  <customControl:Clock x:Name="customControlClock" FontFamily="Arial" />
  <customControl:Clock x:Name="customControlAnalogClock" Style="{StaticResource AnalogClock}" RenderTransformOrigin="0.388,0.66" Width="121" Height="112" />
 </StackPanel>
</Window>
(已用粗体标注重要的部分)

比较一下使用GDI+和WPF的方便性，从设计的角度来讲，WPF显得更方便，更快捷。从编程的代码量相比，两者差别不是太多，我统计了一下总体代码量，GDI+甚至比WPF更少。运行效率方面，暂未做测试。