Windows Phone 7自定义一个控件库跟Silverlight的是基本一样的，第一步创建一个类库，然后添加一个Themes文件夹，在文件夹里面添加上generic.xaml文件作为默认的控件样式文件，记住一定要写这个名字否则就找不到样式了，大小写都可以。新建一个控件类MyContro1.cs,MyContro2.cs在这里面就可以写控件的处理逻辑了。

下面看一下一个水印控件的处理：

generic.xaml文件

WatermarkTextBox..cs

using System.Windows; using System.Windows.Controls; namespace Phone.Controls {
   public class WatermarkedTextBox : TextBox     {
           ContentControl WatermarkContent; public static readonly DependencyProperty WatermarkProperty =       DependencyProperty.Register("Watermark", typeof(object), typeof(WatermarkedTextBox), new PropertyMetadata(OnWatermarkPropertyChanged)); public static readonly DependencyProperty WatermarkStyleProperty =       DependencyProperty.Register("WatermarkStyle", typeof(Style), typeof(WatermarkedTextBox), null); public Style WatermarkStyle         {
   get { return base.GetValue(WatermarkStyleProperty) as Style; } set { base.SetValue(WatermarkStyleProperty, value); }         } public object Watermark         {
   get { return base.GetValue(WatermarkProperty) as object; } set { base.SetValue(WatermarkProperty, value); }         } public WatermarkedTextBox()         {
               DefaultStyleKey = typeof(WatermarkedTextBox);         } public override void OnApplyTemplate()         {
   base.OnApplyTemplate(); this.WatermarkContent = this.GetTemplateChild("watermarkContent") as ContentControl; if(WatermarkContent != null)             {
                 DetermineWatermarkContentVisibility();             }         } protected override void OnGotFocus(RoutedEventArgs e)         {
   if (WatermarkContent != null && string.IsNullOrEmpty(this.Text))             {
   this.WatermarkContent.Visibility = Visibility.Collapsed;             } base.OnGotFocus(e);         } protected override void OnLostFocus(RoutedEventArgs e)         {
   if (WatermarkContent != null && string.IsNullOrEmpty(this.Text))             {
   this.WatermarkContent.Visibility = Visibility.Visible;             } base.OnLostFocus(e);         } private static void OnWatermarkPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)         {
               WatermarkedTextBox watermarkTextBox = sender as WatermarkedTextBox; if(watermarkTextBox != null && watermarkTextBox.WatermarkContent !=null)             {
                 watermarkTextBox.DetermineWatermarkContentVisibility();             }         } private void DetermineWatermarkContentVisibility()         {
   if (string.IsNullOrEmpty(this.Text))             {
   this.WatermarkContent.Visibility = Visibility.Visible;             } else             {
   this.WatermarkContent.Visibility = Visibility.Collapsed;             }         }     } }