GroupStyle.HeaderStringFormat Proprietà

public:
 property System::String ^ HeaderStringFormat { System::String ^ get(); void set(System::String ^ value); };

public string HeaderStringFormat { get; set; }

member this.HeaderStringFormat : string with get, set

Public Property HeaderStringFormat As String

Valore della proprietà

Stringa composita che specifica come formattare l'intestazione se visualizzata come stringa.

Esempio

Nell'esempio seguente viene creato un oggetto ListBox che raggruppa una raccolta di elementi per intervallo di prezzi. Il convertitore, GroupByPrice, restituisce un valore intero superiore al prezzo di ogni elemento. Ad esempio, se il prezzo di un elemento è compreso tra 0 e 100, il convertitore restituisce 100. Nell'esempio HeaderStringFormat viene usato per creare una stringa che include il limite superiore per ogni intervallo di prezzi. Nell'Stati Uniti, ad esempio, gli elementi con un valore inferiore a 100 dollari vengono raggruppati sotto un titolo che indica "Elementi con $100".

<StackPanel>
  <StackPanel.Resources>

      <src:ItemsForSale x:Key="MyData"/>
      <src:GroupByPrice x:Key="GroupByPrice"/>
  
      <CollectionViewSource x:Key="PriceGroup" Source="{StaticResource MyData}">
      
        <CollectionViewSource.GroupDescriptions>
          <PropertyGroupDescription PropertyName="Price"
                                    Converter="{StaticResource GroupByPrice}"/>
      </CollectionViewSource.GroupDescriptions>
    </CollectionViewSource>
  </StackPanel.Resources>
  
  <ListBox ItemsSource="{Binding Source={StaticResource PriceGroup}}"
           DisplayMemberPath="Description">
    <ListBox.GroupStyle>
      <GroupStyle HeaderStringFormat="Items under {0:c}"/>
    </ListBox.GroupStyle>
  </ListBox>
</StackPanel>

Nell'esempio seguente viene illustrata la classe, la PurchaseItem classe e l'insieme GroupByPrice a cui ListBox è associato.

// The converter to group the items.
public class GroupByPrice : IValueConverter
{
    public object Convert(object value,
                          Type targetType,
                          object parameter,
                          System.Globalization.CultureInfo culture)
    {

        if (!(value is double))
        {
            return null;
        }

        double itemPrice = (double)value;

        if (itemPrice < 100)
        {
            return 100;
        }

        if (itemPrice < 250)
        {
            return 250;
        }

        if (itemPrice < 500)
        {
            return 500;
        }

        return 1000;
    }

    public object ConvertBack(object value,
                              Type targetType,
                              object parameter,
                              System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

// The type of objects that are added to the ItemsControl.
public class PurchaseItem 
{
    public string Description { get; set; }
    public double Price { get; set; }
    public DateTime OfferExpires { get; set; }

    public PurchaseItem()
    {
    }

    public PurchaseItem(string desc, double price, DateTime endDate)
    {
        Description = desc;
        Price = price;
        OfferExpires = endDate;
    }

    public override string ToString()
    {
        return String.Format("{0}, {1:c}, {2:D}", Description, Price, OfferExpires);
    }
}

// The source of the ItemsControl.
public class ItemsForSale : ObservableCollection<PurchaseItem>
{

    public ItemsForSale()
    {
        Add((new PurchaseItem("Snowboard and bindings", 120, new DateTime(2009, 1, 1))));
        Add((new PurchaseItem("Inside C#, second edition", 10, new DateTime(2009, 2, 2))));
        Add((new PurchaseItem("Laptop - only 1 year old", 499.99, new DateTime(2009, 2, 28))));
        Add((new PurchaseItem("Set of 6 chairs", 120, new DateTime(2009, 2, 28))));
        Add((new PurchaseItem("My DVD Collection", 15, new DateTime(2009, 1, 1))));
        Add((new PurchaseItem("TV Drama Series", 39.985, new DateTime(2009, 1, 1))));
        Add((new PurchaseItem("Squash racket", 60, new DateTime(2009, 2, 28))));
    }
}

' The converter to group the items.
Public Class GroupByPrice
    Implements IValueConverter
    Public Function Convert(ByVal value As Object, ByVal targetType As Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.Convert

        If Not(TypeOf value Is Double) Then
            Return Nothing
        End If

        Dim itemPrice As Double = CDbl(value)

        If itemPrice < 100 Then
            Return 100
        End If

        If itemPrice < 250 Then
            Return 250
        End If

        If itemPrice < 500 Then
            Return 500
        End If

        Return 1000



    End Function

    Public Function ConvertBack(ByVal value As Object, ByVal targetType As Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack
        Throw New NotImplementedException()
    End Function
End Class

' The type of objects that are added to the ItemsControl.
Public Class PurchaseItem
    Public Property Description() As String
    Public Property Price() As Double
    Public Property OfferExpires() As Date

    Public Sub New()
    End Sub

    Public Sub New(ByVal desc As String, ByVal price As Double, ByVal endDate As Date)
        Description = desc
        Me.Price = price
        OfferExpires = endDate
    End Sub

    Public Overrides Function ToString() As String
        Return String.Format("{0}, {1:c}, {2:D}", Description, Price, OfferExpires)
    End Function
End Class

' The source of the ItemsControl.
Public Class ItemsForSale
    Inherits ObservableCollection(Of PurchaseItem)

    Public Sub New()
        Add((New PurchaseItem("Snowboard and bindings", 120, New Date(2009, 1, 1))))
        Add((New PurchaseItem("Inside VB, second edition", 10, New Date(2009, 2, 2))))
        Add((New PurchaseItem("Laptop - only 1 year old", 499.99, New Date(2009, 2, 28))))
        Add((New PurchaseItem("Set of 6 chairs", 120, New Date(2009, 2, 28))))
        Add((New PurchaseItem("My DVD Collection", 15, New Date(2009, 1, 1))))
        Add((New PurchaseItem("TV Drama Series", 39.985, New Date(2009, 1, 1))))
        Add((New PurchaseItem("Squash racket", 60, New Date(2009, 2, 28))))

    End Sub

End Class

Commenti

HeaderStringFormat può essere un formato stringa predefinito, composito o personalizzato. Per altre informazioni sui formati di stringa, vedere Tipi di formattazione. Se si imposta la HeaderTemplate proprietà o HeaderTemplateSelector di un GroupStyleoggetto , la HeaderStringFormat proprietà viene ignorata.

Si applica a