public class ForumInfo
{
    public int ForumID { get; set; }
    public int ParendID { get; set; }
    public string ForumName { get; set; }
}

[ServiceContract(Namespace = "")]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class DateService
{
 
    [OperationContract]
    public List<ForumInfo> GetForumData()
    {
        List<ForumInfo> forumList = new List<ForumInfo>();
        forumList.Add(new ForumInfo() { ForumID = 1, ParendID = 0, ForumName = "笔记本版块"});
        forumList.Add(new ForumInfo() { ForumID = 2, ParendID = 0, ForumName = "台式机版块" });

forumList.Add(new ForumInfo() { ForumID = 3, ParendID = 1, ForumName = "Dell笔记本" });
        forumList.Add(new ForumInfo() { ForumID = 4, ParendID = 1, ForumName = "IBM笔记本" });
        forumList.Add(new ForumInfo() { ForumID = 5, ParendID = 4, ForumName = "IBM-T系列" });
        forumList.Add(new ForumInfo() { ForumID = 6, ParendID = 4, ForumName = "IBM-R系列" });

forumList.Add(new ForumInfo() { ForumID = 7, ParendID = 2, ForumName = "联想台式机" });
        forumList.Add(new ForumInfo() { ForumID = 8, ParendID = 2, ForumName = "方正台式机" });
        forumList.Add(new ForumInfo() { ForumID = 9, ParendID = 2, ForumName = "HP台式机" });
        forumList.Add(new ForumInfo() { ForumID = 10, ParendID = 7, ForumName = "联想家悦H系列" });
        forumList.Add(new ForumInfo() { ForumID = 11, ParendID = 7, ForumName = "联想IdeaCentre系列" });

return forumList;
    }
}

<controls:TreeView x:Name="TreeOfLife" Margin="5" Grid.Column="0" Grid.Row="1"  
          SelectedItemChanged="TreeOfLife_SelectedItemChanged" />

<Border BorderBrush="Gray" BorderThickness="1" Padding="8" Margin="8,0,0,0" Grid.Row="1" Grid.Column="1">
    <StackPanel x:Name="DetailsPanel" Margin="4">
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="版块ID: " FontWeight="Bold"  />
            <TextBlock Text="{Binding ForumID}" />
        </StackPanel>
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="版块名称: " FontWeight="Bold"  />
            <TextBlock Text="{Binding ForumName}" />
        </StackPanel>
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="版块信息: " FontWeight="Bold" />
            <TextBlock x:Name="DetailText" TextWrapping="Wrap" Text="{Binding ForumName}"/>
        </StackPanel>
    </StackPanel>
</Border>

public partial class Page : UserControl
{
     DateServiceClient dataServiceClient = new DateServiceClient();

ObservableCollection<ForumInfo> forumList = new ObservableCollection<ForumInfo>();

public Page()
     {
         InitializeComponent();

//此样式只添加在根结点上
         //TreeOfLife.ItemContainerStyle = this.Resources["RedItemStyle"] as Style;
              
         dataServiceClient.GetForumDataCompleted+=new EventHandler<GetForumDataCompletedEventArgs>(dataServiceClient_GetForumDataCompleted);
         dataServiceClient.GetForumDataAsync();
     }

void dataServiceClient_GetForumDataCompleted(object sender, GetForumDataCompletedEventArgs e)
     {
         try
         {
             forumList = e.Result;
             AddTreeNode(0, null);  
         }
         catch
         {
             throw new NotImplementedException();
         }
     }

private void AddTreeNode(int parentID, TreeViewItem treeViewItem)
     {
         List<ForumInfo> result = (from forumInfo in forumList
                                   where forumInfo.ParendID == parentID
                                   select forumInfo).ToList<ForumInfo>();

if (result.Count > 0)
         {
             foreach (ForumInfo foruminfo in result)
             {
                 TreeViewItem objTreeNode = new TreeViewItem();
                 objTreeNode.Header = foruminfo.ForumName;
                 objTreeNode.DataContext = foruminfo;

//此样式将会添加的所有叶子结点上
                 //objTreeNode.ItemContainerStyle = this.Resources["RedItemStyle"] as Style;
 
                 //添加根节点
                 if (treeViewItem == null)
                 {
                     TreeOfLife.Items.Add(objTreeNode);
                 }
                 else
                 {                    
                     treeViewItem.Items.Add(objTreeNode);
                 }
                 AddTreeNode(foruminfo.ForumID, objTreeNode);
             }
         }
     }

private void TreeOfLife_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
     {
         TreeViewItem item = e.NewValue as TreeViewItem;
         ForumInfo fi = item.DataContext as ForumInfo;

DetailsPanel.DataContext = fi;
     }
}

<UserControl.Resources>
        <Style x:Key="RedItemStyle" TargetType="controls:TreeViewItem">
            <Setter Property="HeaderTemplate">
                <Setter.Value>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <CheckBox />
                            <Image Source="image/default.png"/>
                            <TextBlock Text="{Binding}" Foreground="Red" FontStyle="Italic" />
                        </StackPanel>
                    </DataTemplate>
                </Setter.Value>
            </Setter>
            <Setter Property="IsExpanded" Value="True" />
        </Style>
</UserControl.Resources>

TreeOfLife.ItemContainerStyle = this.Resources["RedItemStyle"] as Style; 

当前TreeView中定义样式模版还可以使用ItemTemplate，下面是一段样式代码: 

<controls:TreeView.ItemTemplate>
    <controls:HierarchicalDataTemplate ItemsSource="{Binding Subclasses}"
            ItemContainerStyle="{StaticResource ExpandedItemStyle}">
        <StackPanel>
            <TextBlock Text="{Binding Rank}" FontSize="8" FontStyle="Italic" Foreground="Gray" Margin="0 0 0 -5" />
            <TextBlock Text="{Binding Classification}" />
        </StackPanel>
    </controls:HierarchicalDataTemplate>
</controls:TreeView.ItemTemplate>