How to show big data without hitting memory limit?

Question

I want to show a very long list of comments, which contains text, image, username, etc, in a LongListSelector using binding.

Can get all comments by one request only. when I show those comments, app hits memory limit and exits.

<phone:LongListSelector ItemsSource="{Binding Comments}">
    <phone:LongListSelector.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                    <TextBlock Text="{Binding Username}"/>
                    <TextBlock Text="{Binding Text"/>
                    <TextBlock Text="{Binding Date}"/>
            </StackPanel>
        </DataTemplate>
    </phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>

What can I do in this scenario? thanks.