Artigo
11/18/2011

BindingExpression Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Contains information about a single binding within a Binding object.

Inheritance Hierarchy

System.Object
  System.Windows.Expression
    System.Windows.Data.BindingExpressionBase
      System.Windows.Data.BindingExpression

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

Syntax

'Declaration
Public NotInheritable Class BindingExpression _
    Inherits BindingExpressionBase

public sealed class BindingExpression : BindingExpressionBase

The BindingExpression type exposes the following members.

Properties

	Name	Description
	DataItem	Gets the binding source object that this BindingExpression uses.
	ParentBinding	Returns the Binding object of the current BindingExpression.

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Methods

	Name	Description
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)
	UpdateSource	Sends the current binding target value to the binding source property in TwoWay bindings.

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Remarks

A Binding object can be used by multiple binding targets. The BindingExpression class, however, represents a single binding. You can retrieve a BindingExpression instance from a binding target by calling its FrameworkElement.GetBindingExpression method. You can then use the BindingExpression to call the UpdateSource method. This is useful to control when values are copied from the binding target to the binding source. For more information, see Data Binding.

Examples

The following code example demonstrates how to use this method.

<TextBox x:Name="textBox1" Text="{Binding Test, Mode=TwoWay, UpdateSourceTrigger=Explicit}" />
<Button Content="Update" Click="Button_Click" />

Public Class TestData
    Private testValue As String
    Public Property Test() As String
        Get
            Return testValue
        End Get
        Set(ByVal value As String)
            testValue = value
        End Set
    End Property
End Class

Private data As TestData

Public Sub New()

    InitializeComponent()

    data = New TestData
    With data
        .Test = "one"
    End With

    textBox1.DataContext = data

End Sub

Private Sub Button_Click(ByVal sender As Object, _
    ByVal e As RoutedEventArgs)

    Dim expression As BindingExpression = _
        textBox1.GetBindingExpression(TextBox.TextProperty)
    MessageBox.Show("Before UpdateSource, Test = " & data.Test)
    expression.UpdateSource()
    MessageBox.Show("After UpdateSource, Test = " & data.Test)

End Sub

public class TestData
{
    public String Test { get; set; }
}

TestData data;

public MainPage()
{
    InitializeComponent();
    data = new TestData { Test = "one" };
    textBox1.DataContext = data;
}

private void Button_Click(object sender, RoutedEventArgs e)
{
    BindingExpression expression = textBox1.GetBindingExpression(TextBox.TextProperty);
    MessageBox.Show("Before UpdateSource, Test = " + data.Test);
    expression.UpdateSource();
    MessageBox.Show("After UpdateSource, Test = " + data.Test);
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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