Question

I’m currently learning how to develop and building an app for windows phone 7.

If a certain value is true, I need to add a TextBlock to the ListBox before a TextBlock (say its name is x:Name="dayTxtBx").

I am currently using

dayListBox.Items.Add(dayTxtBx);

to add the text box.

Any help very much appreciated!

Thanks

Answer 1

This is pretty easy to do if you’re using a DataTemplate and a ValueConverter and passing the whole object into the ListBox (rather than just a string). Assuming you have some object that looks like:

public class SomeObject: INotifyPropertyChanged
{
    private bool mTestValue;
    public bool TestValue 
    {
        get {return mTestValue;}
        set {mTestValue = value; NotifyPropertyChanged("TestValue");}
    }
    private string mSomeText;
    public string SomeText
    {
        get {return mSomeText;}
        set {mSomeText = value; NotifyPropertyChanged("SomeText");}
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(string name)
    {
        if ((name != null) && (PropertyChanged != null))
        {
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
    }
}

You can make a converter that looks like:

public class BooleanVisibilityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value != null && (bool)value)
            return Visibility.Visible;
        else
            return Visibility.Collapsed;
    }
    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

And add the converter to your XAML like so:

<UserControl x:Class="MyProject.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:MyProject">
    <UserControl.Resources>
        <local:BooleanVisibilityConverter x:Key="BoolVisibilityConverter" />
    <UserControl.Resources>

Then you could have the ListBox defined in XAML like so:

<Listbox>
  <Listbox.ItemTemplate>
    <DataTemplate>
      <StackPanel Orentation="Horizontal" >
        <TextBlock Text="Only Show If Value is True" Visibility={Binding TestValue, Converter={StaticResource BoolVisibilityConverter}} />
        <TextBlock Text="{Binding SomeText}" />
      </StackPanel>
    </DataTemplate>
  </Listbox.ItemTemplate>
</Listbox>

Might seem like a lot, but it’s really pretty simple once you get started. A great way to learn more about data binding and converters is at Jesse Liberty’s blog ( http://jesseliberty.com/?s=Windows+Phone+From+Scratch ).