BindingSource Class (System.Windows.Forms)

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Microsoft Visual Studio 2005/.NET Framework 2.0

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.NET Framework Class Library

BindingSource Class

Note: This class is new in the .NET Framework version 2.0.

Encapsulates the data source for a form.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

Syntax

Visual Basic (Declaration)

Public Class BindingSource
    Inherits Component
    Implements IBindingListView, IBindingList, IList, ICollection, _
    IEnumerable, ITypedList, ICancelAddNew, ISupportInitializeNotification, ISupportInitialize, _
    ICurrencyManagerProvider

Visual Basic (Usage)

Dim instance As BindingSource

public class BindingSource : Component, IBindingListView, IBindingList, IList, 
    ICollection, IEnumerable, ITypedList, ICancelAddNew, ISupportInitializeNotification, 
    ISupportInitialize, ICurrencyManagerProvider

C++

public ref class BindingSource : public Component, IBindingListView, IBindingList, IList, 
    ICollection, IEnumerable, ITypedList, ICancelAddNew, ISupportInitializeNotification, 
    ISupportInitialize, ICurrencyManagerProvider

public class BindingSource extends Component implements IBindingListView, IBindingList, 
    IList, ICollection, IEnumerable, ITypedList, ICancelAddNew, 
    ISupportInitializeNotification, ISupportInitialize, ICurrencyManagerProvider

JScript

public class BindingSource extends Component implements IBindingListView, IBindingList, 
    IList, ICollection, IEnumerable, ITypedList, ICancelAddNew, 
    ISupportInitializeNotification, ISupportInitialize, ICurrencyManagerProvider

Remarks

The BindingSource component serves two purposes. First, it simplifies binding controls on a form to data by providing a layer of indirection, currency management, change notification, and other services. This is accomplished by attaching the BindingSource component to your data source, and then binding the controls on your form to the BindingSource component. All further interaction with the data, including navigating, sorting, filtering, and updating, is accomplished with calls to the BindingSource component.

Second, the BindingSource component can act as a strongly typed data source. Typically the type of the underlying data source is fixed through one of the following mechanisms:

Use the Add method to add an item to the BindingSource component.
Set the DataSource property to a list, single object, or type.

Both of these mechanisms create a strongly-typed list. BindingSource supports both simple and complex data binding as indicated by its DataSource and DataMember properties.

Note
Because a BindingSource handles both simple and complex data sources, terminology is problematic. Within this class documentation, the term list refers to a data collection within the hosted data source, and item denotes a single element. When discussing functionality associated with complex data sources, the equivalent terms table and row are used.

BindingSource provides members for accessing the underlying data. The current item can be retrieved through the Current property, and the entire list can be retrieved through the List property. Editing operations are supported on the current item through Current and the RemoveCurrent, EndEdit, CancelEdit and Add and AddNew methods. Although currency management is handled automatically for all underlying data source types, this class exposes a number of events, such as CurrentItemChanged and DataSourceChanged, that allow for customization.

Data sources that are bound to a BindingSource component can also be navigated and managed with the BindingNavigator class, which provides a VCR-like user interface (UI) for navigating items within a list. Although BindingNavigator can be bound to any data source, it was designed to integrate with a BindingSource component through its BindingNavigator.BindingSource property.

The default property for the BindingSource class is DataSource. The default event is CurrentChanged.

Caution
Many of the members of the BindingSource class operate on the underlying list represented by the List property and simply refer their operation to the underlying list. Therefore, when the BindingSource is bound to a custom implementation of IList, the exact behavior of these members may differ from the behavior described in the class documentation. For example, the RemoveAt method calls IList.RemoveAt. The BindingSource documentation describes the RemoveAt method with the understanding that the RemoveAt method for the underlying IList is correctly implemented.

Caution

Many of the members of the BindingSource class operate on the underlying list represented by the List property and simply refer their operation to the underlying list. Therefore, when the BindingSource is bound to a custom implementation of IList, the exact behavior of these members may differ from the behavior described in the class documentation. For example, the RemoveAt method calls IList.RemoveAt. The BindingSource documentation describes the RemoveAt method with the understanding that the RemoveAt method for the underlying IList is correctly implemented.

Example

The following code example demonstrates a ListBox bound to a BindingSource. The BindingSource is bound to a BindingList that contains a list of fonts.

Visual Basic

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms
Public Class Form1
    Inherits Form

    <STAThread()> _
    Shared Sub Main()
        Application.EnableVisualStyles()
        Application.Run(New Form1())

    End Sub

    Public Sub New()

    End Sub

    Private textBox1 As TextBox
    Private WithEvents button1 As Button
    Private listBox1 As ListBox
    Private components As IContainer
    Private binding1 As BindingSource

    Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
        listBox1 = New ListBox()
        textBox1 = New TextBox()
        binding1 = New BindingSource()
        button1 = New Button()
        listBox1.Location = New Point(140, 25)
        listBox1.Size = New Size(123, 160)
        textBox1.Location = New Point(23, 70)
        textBox1.Size = New Size(100, 20)
        textBox1.Text = "Wingdings"
        button1.Location = New Point(23, 25)
        button1.Size = New Size(75, 23)
        button1.Text = "Search"
        Me.ClientSize = New Size(292, 266)
        Me.Controls.Add(Me.button1)
        Me.Controls.Add(Me.textBox1)
        Me.Controls.Add(Me.listBox1)

        Dim fonts As New MyFontList()
        Dim i As Integer
        For i = 0 To FontFamily.Families.Length - 1
            If FontFamily.Families(i).IsStyleAvailable(FontStyle.Regular) Then
                fonts.Add(New Font(FontFamily.Families(i), 11.0F, FontStyle.Regular))
            End If
        Next i
        binding1.DataSource = fonts
        listBox1.DataSource = binding1
        listBox1.DisplayMember = "Name"

    End Sub
    Private Sub button1_Click(ByVal sender As Object, ByVal e As EventArgs) _
        Handles button1.Click

        If binding1.SupportsSearching <> True Then
            MessageBox.Show("Cannot search the list.")
        Else
            Dim foundIndex As Integer = binding1.Find("Name", textBox1.Text)
            If foundIndex > -1 Then
                listBox1.SelectedIndex = foundIndex
            Else
                MessageBox.Show("Font was not found.")
            End If
        End If

    End Sub
End Class

Public Class MyFontList
    Inherits BindingList(Of Font)

    Protected Overrides ReadOnly Property SupportsSearchingCore() As Boolean
        Get
            Return True
        End Get
    End Property
    
    Protected Overrides Function FindCore(ByVal prop As PropertyDescriptor, _
        ByVal key As Object) As Integer
        ' Ignore the prop value and search by family name.
        Dim i As Integer
        While i < Count
            If Items(i).FontFamily.Name.ToLower() = CStr(key).ToLower() Then
                Return i
            End If
            i += 1
        End While

        Return -1
    End Function
End Class

Inheritance Hierarchy

System.Object
   System.MarshalByRefObject
     System.ComponentModel.Component
      System.Windows.Forms.BindingSource

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.

Platforms

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

Version Information