问一个数据绑定的初级有关问题.求大大帮解答~

问一个数据绑定的初级问题....求大大帮解答~~
我用webservice 获取到数据后  然后添加到ObservableCollection这个集合里面
如下
ObservableCollection<Announcement> list = new ObservableCollection<Announcement>()

然后绑定

<phone:PanoramaItem Header="公告" Width="420" Loaded="PanoramaItem_Loaded">
                <ListBox Name="ggList" 
                         ItemTemplate="{StaticResource GgListBoxDatatemplate}" >
                </ListBox>
            </phone:PanoramaItem>

下面是DataTemplate

<DataTemplate x:Key="GgListBoxDatatemplate">
            <Grid >
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="20"/>
                    <ColumnDefinition Width="auto"/>
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                </Grid.RowDefinitions>
                
                <TextBlock Text="对象" FontSize="9pt" Grid.Row="1" Grid.Column="0"></TextBlock>
                <TextBlock x:Name="TxtTo" Text="{Binding To}" Grid.Row="1" Grid.Column="1"></TextBlock>
                
                <TextBlock Text="内容" FontSize="9pt" Grid.Row="2" Grid.Column="0"></TextBlock>
                <TextBlock x:Name="TxtContent" Text="{Binding Content}" Grid.Row="2" Grid.Column="1"></TextBlock>
                
                <TextBlock Grid.Row="3" Text="{Binding CreateTime}" Grid.Column="0" Grid.ColumnSpan="2"></TextBlock>
            </Grid>
        </DataTemplate>