LongListSelector + Selected Item-如何读取每个单独的属性？ （WP8，Azure数据库）

Question

I have a LongListSelector, that store data from my Azure SQL Database.

This is my C# code:

 private async void RefreshTodoItemsToday()
    {
        try
        {
            coll = await todoTable
                .Where(todoItem => todoItem.TpEvt == "today")
                .ToCollectionAsync();
        }
        catch (MobileServiceInvalidOperationException e)
        {
            MessageBox.Show(e.Message, "Error loading items", MessageBoxButton.OK);
        }

        ListItemstoday.ItemsSource = coll;
    }

And this is my XAML:

<phone:LongListSelector Name="ListItemsToday">
                <phone:LongListSelector.ItemTemplate>
                    <DataTemplate>
                        <StackPanel>

                                <TextBlock Name="TxtEvt" Text="{Binding Text}" TextWrapping="Wrap" Foreground="Gray" TextAlignment="Center" FontSize="30" Padding="30">
                                </TextBlock>

                        <Line X1="0" Y1="10" X2="240" Y2="10" Stroke="SkyBlue" HorizontalAlignment="Center" VerticalAlignment="Center" Height="21"/>
                        </StackPanel>
                    </DataTemplate>
                </phone:LongListSelector.ItemTemplate>
                </phone:LongListSelector>

The registers are stored in my LongListSelector - it is working fine.

Now this is my doubt: How can i read the properties for each register in my LongListSelector? For each register, i have fields such as "Id", "TypeEvent", "Hour", "Date", etc.

So, how can i read each individual value, according by the SelectedItem in LongListSelector?

For example, if i wish to see in a MessageBox the ID from a Selected Item...how can i do this in code?

I tried the following:

var tmp1 = (TodoItem)ListItemsToday.SelectedItem; 
var tmp2 = tmp1.Id;
MessageBox.Show(tmp2.ToString());

When i try to cast this code, this is the error i got:

*System.NullReferenceException: Object reference not set to an instance of an object. at Project.MainPage.ContextMenuRemove_Click(Object sender, EventArgs e)*

Someone can help'me, please? Thank you friends.

Answer 1

React to selection changed:

<phone:LongListSelector Name="ListItemsToday" SelectionChanged="ListItemsToday_SelectionChanged">
    <phone:LongListSelector.ItemTemplate>
        <DataTemplate>
            <StackPanel>

                <TextBlock Name="TxtEvt" Text="{Binding Text}" TextWrapping="Wrap" Foreground="Gray" TextAlignment="Center" FontSize="30" Padding="30">
                </TextBlock>

                <Line X1="0" Y1="10" X2="240" Y2="10" Stroke="SkyBlue" HorizontalAlignment="Center" VerticalAlignment="Center" Height="21"/>
            </StackPanel>
        </DataTemplate>
    </phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>

with this

private void ListItemsToday_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    var item = ListItemsToday.SelectedItem as TodoItem;
    MessageBox.Show(item.Text);
}

Or react to tap event in data template

<phone:LongListSelector Name="ListItemsToday" >
    <phone:LongListSelector.ItemTemplate>
        <DataTemplate>
            <StackPanel Tap="ListItemsToday_Tap">

                <TextBlock Name="TxtEvt" Text="{Binding Text}" TextWrapping="Wrap" Foreground="Gray" TextAlignment="Center" FontSize="30" Padding="30">
                </TextBlock>

                <Line X1="0" Y1="10" X2="240" Y2="10" Stroke="SkyBlue" HorizontalAlignment="Center" VerticalAlignment="Center" Height="21"/>
            </StackPanel>
        </DataTemplate>
    </phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>

like this:

private void ListItemsToday_Tap(object sender, System.Windows.Input.GestureEventArgs e)
{
    var item = (sender as FrameworkElement).DataContext as TodoItem;
    MessageBox.Show(item.Text);
}