wp8 longlistselector 动态加载datatemplate

在做一个windows phone 8 即时通讯应用的时候，聊天界面的对话气泡。 需要根据不同的消息类型，加载对应的DataTemplate,
比如发送，接受，图片，语音，等气泡。 如下图所示

会话界面

主要思想就是，定义多个不同的模板，在每一项的内容生成的时候，根据数据源的类型，加载对应的模板。

看代码

public abstract class DataTemplateSelector:ContentControl
    {
            //根据newContent的属性，返回所需的DataTemplate
            public virtual DataTemplate SelectTemplate(object item, DependencyObject container)
            {
                return null;
            }

            protected override void OnContentChanged(object oldContent, object newContent)
            {
                base.OnContentChanged(oldContent, newContent);
                //根据newContent的属性，选择对应的DataTemplate
                ContentTemplate = SelectTemplate(newContent, this);
            }

    }
    public class ChatTemplateSelector : DataTemplateSelector
    {
        public DataTemplate ReciveMsgTP { get; set; }
        public DataTemplate SendMsgTP { get; set; }

        //根据newContent的属性，返回所需的DataTemplate
        public override DataTemplate SelectTemplate(object item, DependencyObject container)
        {
            ChatModel model = item as ChatModel;
            DataTemplate dt;
            if (model != null)
            {
                switch (model.CMType)
                {
                    case MessageType.ReciveMsg:
                        dt= ReciveMsgTP;
                        break;
                    case MessageType.SendMsg:
                        dt= SendMsgTP;
                        break;
                    default:
                        dt = ReciveMsgTP; 
                        break;
                }
                return dt;
            }
            return base.SelectTemplate(item, container);
        }
    }

.xaml

<phone:PhoneApplicationPage.Resources>
        <DataTemplate x:Key="ItemTP">
            <local:ChatTemplateSelector  Content="{Binding}">
                <local:ChatTemplateSelector.ReciveMsgTP>
                    <DataTemplate>
                        <Grid d:DesignWidth="415.522" d:DesignHeight="106.567" Height="113" Width="501">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="124*"/>
                                <ColumnDefinition Width="43*"/>
                            </Grid.ColumnDefinitions>
                            <TextBlock Grid.Column="1" HorizontalAlignment="Left" Margin="10,10,0,0" TextWrapping="Wrap" Text="{Binding Msg}" VerticalAlignment="Top" FontSize="30" Height="0" Width="0"/>
                            <Border BorderBrush="Black" BorderThickness="1" HorizontalAlignment="Left" Height="100" Margin="10,3,0,0" VerticalAlignment="Top" Width="315" Background="#FFF56D6D"/>
                        </Grid>
                    </DataTemplate>

                </local:ChatTemplateSelector.ReciveMsgTP>
                <local:ChatTemplateSelector.SendMsgTP>
                    <DataTemplate>
                        <Grid d:DesignWidth="415.522" d:DesignHeight="106.567" Height="128" Width="498">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="59*"/>
                                <ColumnDefinition Width="190*"/>
                            </Grid.ColumnDefinitions>
                            <TextBlock Grid.Column="1" HorizontalAlignment="Left" Margin="10,10,0,0" TextWrapping="Wrap" Text="{Binding Msg}" VerticalAlignment="Top" FontSize="30" Height="0" Width="0"/>
                            <Border BorderBrush="Black" BorderThickness="1" Grid.Column="1" HorizontalAlignment="Left" Height="100" Margin="10,15,0,0" VerticalAlignment="Top" Width="348" Background="#FF0F7DEC"/>
                        </Grid>
                    </DataTemplate>
                </local:ChatTemplateSelector.SendMsgTP>
            </local:ChatTemplateSelector>
        </DataTemplate>
    </phone:PhoneApplicationPage.Resources>