GroupStyle.HeaderStringFormat 属性

定义

命名空间:

System.Windows.Controls

程序集:

PresentationFramework.dll

获取或设置一个撰写字符串，该字符串指定如果标题显示为字符串，应如何设置该标题的格式。

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

属性值

String

一个撰写字符串，指定如果标题显示为字符串，应如何设置该标题的格式。

示例

以下示例创建一个 ListBox 按价格范围对项目集合进行分组。 转换器 GroupByPrice返回高于每个项目价格的整数值。 例如，如果项的价格介于 0 和 100 之间，则转换器返回 100。 该示例使用创建 HeaderStringFormat 一个字符串，其中包含每个价格范围的上限。 例如，在美国中，100 美元以下的项目分组在标题下，标题显示“100 美元以下的项目”。

<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>

以下示例显示 GroupByPrice 绑定到的类、 PurchaseItem 类和集合 ListBox 。

// 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

注解

HeaderStringFormat 可以是预定义、复合或自定义字符串格式。 有关字符串格式的详细信息，请参阅 格式设置类型。 如果设置 a HeaderTemplate GroupStyle或HeaderTemplateSelector属性，则忽略该HeaderStringFormat属性。