FrameworkElement.BindingGroup Property

.NET Framework (current version)

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Gets or sets the BindingGroup that is used for the element.

Namespace: System.Windows
Assembly: PresentationFramework (in PresentationFramework.dll)

Syntax

C++

<LocalizabilityAttribute(LocalizationCategory.NeverLocalize)>
Public Property BindingGroup As BindingGroup

Property Value

Type: System.Windows.Data.BindingGroup

The BindingGroup that is used for the element.

A BindingGroup can be used to validate the values of multiple properties of an object. For example, suppose that an application prompts the user to enter an address and then populates an object of type Address, which has the properties Street, City, ZipCode, and Country, with the values that the user provided. The application has a panel that contains four TextBox controls, each of which is bound to one of the object’s properties. You can use a ValidationRule in a BindingGroup to validate the Address object. For example, the ValidationRule can ensure that the zip code is valid for the country of the address.

Child elements inherit the BindingGroup from their parent elements, just as with any other inheritable property.

Dependency Property Information

Identifier field	BindingGroupProperty
Metadata properties set to true	Inherits

Examples

The following examples are part of an application that checks whether the user has set the properties of two objects to equal values. The first example creates two TextBox controls, each of which is bound to a different data source. The StackPanel has a BindingGroup that contains a ValidationRule that checks that the two strings are equal.

XAML

<StackPanel>
  <StackPanel.Resources>
    <src:Type1 x:Key="object1" />
    <src:Type2 x:Key="object2" />
  </StackPanel.Resources>

  <StackPanel Name="sp1"
              Margin="5"
              DataContext="{Binding Source={StaticResource object1}}"
              Validation.ValidationAdornerSite="{Binding ElementName=label1}"
              Orientation="Horizontal"
              HorizontalAlignment="Center">

    <StackPanel.BindingGroup>
      <BindingGroup Name="bindingGroup">
        <BindingGroup.ValidationRules>
          <src:BindingGroupValidationRule ValidatesOnTargetUpdated="True" />
        </BindingGroup.ValidationRules>
      </BindingGroup>
    </StackPanel.BindingGroup>

    <TextBlock Text="First string" />

    <TextBox Width="150"
             Text="{Binding Path=PropertyA}" />

    <TextBlock Text="Second string" />

    <TextBox Width="150"
             Text="{Binding Source={StaticResource object2}, 
      Path=PropertyB, BindingGroupName=bindingGroup, 
      TargetNullValue=please enter a string}" />

  </StackPanel>

  <Label Name="label1"
         Content="{Binding ElementName=sp1, Path=(Validation.Errors)[0].ErrorContent}"
         Margin="5"
         Foreground="Red"
         HorizontalAlignment="Center" />

  <Button HorizontalAlignment="Center"
          Click="Button_Click"
          IsDefault="True">
    _Submit
  </Button>

  <StackPanel Orientation="Horizontal">
    <TextBlock Text="First string:"
               FontWeight="Bold" />
    <TextBlock Text="{Binding Source={StaticResource object1}, 
      Path=PropertyA, TargetNullValue=--}" />
  </StackPanel>

  <StackPanel Orientation="Horizontal">
    <TextBlock Text="Second string:"
               FontWeight="Bold" />
    <TextBlock Text="{Binding Source={StaticResource object2}, 
      Path=PropertyB, TargetNullValue=--}" />
  </StackPanel>
</StackPanel>

The following example shows the ValidationRule that the previous example uses. In the Validate method override, the example gets each source object from the BindingGroup and checks whether the properties of the objects are equal.

Public Class Type1
    Public Property PropertyA() As String

    Public Sub New()
        PropertyA = "Default Value"
    End Sub
End Class

Public Class Type2
    Public Property PropertyB() As String

    Public Sub New()
    End Sub
End Class

Public Class BindingGroupValidationRule
    Inherits ValidationRule
    Public Overrides Function Validate(ByVal value As Object, ByVal cultureInfo As System.Globalization.CultureInfo) As ValidationResult
        Dim bg As BindingGroup = TryCast(value, BindingGroup)

        Dim object1 As Type1 = Nothing
        Dim object2 As Type2 = Nothing

        For Each item As Object In bg.Items
            If TypeOf item Is Type1 Then
                object1 = TryCast(item, Type1)
            End If

            If TypeOf item Is Type2 Then
                object2 = TryCast(item, Type2)
            End If
        Next item

        If object1 Is Nothing OrElse object2 Is Nothing Then
            Return New ValidationResult(False, "BindingGroup did not find source object.")
        End If

        Dim string1 As String = TryCast(bg.GetValue(object1, "PropertyA"), String)
        Dim string2 As String = TryCast(bg.GetValue(object2, "PropertyB"), String)

        If string1 <> string2 Then
            Return New ValidationResult(False, "The two strings must be identical.")
        End If

        Return ValidationResult.ValidResult

    End Function

End Class

To invoke the ValidationRule, call the UpdateSources method. The following example calls UpdateSources when the click event of the button occurs.

Private Sub Button_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
    sp1.BindingGroup.UpdateSources()
End Sub

Version Information

.NET Framework
Available since 3.0