Windows 8 Combobox PlaceholderText - windows-8

Question

i am using "visual studio express for windows 8" and using Combo Box control as
<ComboBox Name="Categories" >
<x:String>apple</x:String>
<x:String>ball</x:String>
<x:String>cat</x:String>
<x:String>dog</x:String>
</ComboBox>
i want to show placeholder text in it to show some text until user hasn't selected any item from it. But when i use property PlaceholderText as described in microsoft reference to show text but when i use it the sdk shows this error
The member "PlaceholderText" is not recognized or is not accessible.
or is there any other method so that i can show some default text in Combobox.
Thanks.

Answer 1

This is for Windows 8.1 preview and not Windows 8 development. You will need to install the preview at this time before you can use and develop with this combobox. Looking at the docs for placeholder it states:
Minimum supported client Windows 8.1 Preview
Edit
To do this manually simply preload the combobox by hand. Here is an example, let us start with the ViewModel where the constructor will load an initial value into the combobox named "Loading"
public class MainVM : INotifyPropertyChanged
{
private List<string> _dataList;
public List<string> ComboData
{
get { return _dataList; }
set
{
if (_dataList != value)
{
_dataList = value;
OnPropertyChanged();
}
}
}
public MainVM()
{
ComboData = new List<string> {"Loading..."};
}
#region INotify Property Changed Implementation
/// <summary>
/// Event raised when a property changes.
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Raises the PropertyChanged event.
/// </summary>
/// <param name="propertyName">The name of the property that has changed.</param>
public void OnPropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
Now on the main page xaml bind to ComboData, but we need to be wary of the first situation where a list of one items will have loading, and we want to make that the selected item.
<ComboBox ItemsSource="{Binding ComboData}" Height="30" Width="300" Loaded="OnLoaded" />
Ok, in the code behind of the page we will set our datacontext to be the ViewModel we setup before, but also have an OnLoaded method which checks for the 1 item loading situation. In the below example we simulate a 3 second delay of loading the rest of the data.
public sealed partial class MainPage : Page
{
public MainVM ViewModel { get; set; }
public MainPage()
{
this.InitializeComponent();
DataContext = ViewModel = new MainVM();
}
private void OnLoaded(object sender, RoutedEventArgs e)
{
var cBox = sender as ComboBox;
if (cBox != null)
{
if ((cBox.Items != null) && (cBox.Items.Count == 1))
{
cBox.SelectedIndex = 0;
// Debug code to simulate a change
Task.Run(() =>
{
// Sleep 3 seconds
new System.Threading.ManualResetEvent(false).WaitOne(3000);
Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{ ViewModel.ComboData = new List<string> {"Alpha", "Gamma", "Omega"}; });
});
}
}
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
}
}