How to: Raise Change Notifications Using the BindingSource ResetItem Method

Artikel
02/06/2023

Some data sources for your controls do not raise change notifications when items are changed, added, or deleted. With the BindingSource component, you can bind to such data sources and raise a change notification from your code.

Example

This form demonstrates using a BindingSource component to bind a list to a DataGridView control. The list does not raise change notifications, so the ResetItem method on the BindingSource is called when an item in the list is changed. .

#using <System.dll>
#using <System.Data.dll>
#using <System.Drawing.dll>
#using <System.EnterpriseServices.dll>
#using <System.Transactions.dll>
#using <System.Windows.Forms.dll>
#using <System.Xml.dll>

using namespace System;
using namespace System::Collections::Generic;
using namespace System::ComponentModel;
using namespace System::Data;
using namespace System::Data::Common;
using namespace System::Data::SqlClient;
using namespace System::Diagnostics;
using namespace System::Drawing;
using namespace System::Windows::Forms;

// This class implements a simple customer type.
public ref class DemoCustomer
{
private:
   // These fields hold the values for the public properties.
   Guid idValue;
   String^ customerName;
   String^ companyNameValue;
   String^ phoneNumberValue;

   // The constructor is private to enforce the factory pattern.
   DemoCustomer()
   {
      idValue = Guid::NewGuid();
      customerName = L"no data";
      companyNameValue = L"no data";
      phoneNumberValue = L"no data";
   }

public:
   // This is the public factory method.
   static DemoCustomer^ CreateNewCustomer()
   {
      return gcnew DemoCustomer;
   }

   property Guid ID 
   {
      // This property represents an ID, suitable
      // for use as a primary key in a database.
      Guid get()
      {
         return this->idValue;
      }
   }

   property String^ CompanyName 
   {
      String^ get()
      {
         return this->companyNameValue;
      }

      void set( String^ value )
      {
         this->companyNameValue = value;
      }
   }

   property String^ PhoneNumber 
   {
      String^ get()
      {
         return this->phoneNumberValue;
      }

      void set( String^ value )
      {
         this->phoneNumberValue = value;
      }
   }
};

// This form demonstrates using a BindingSource to bind
// a list to a DataGridView control. The list does not
// raise change notifications, so the ResetItem method
// on the BindingSource is used.
public ref class Form1: public System::Windows::Forms::Form
{
private:
   // This button causes the value of a list element to be changed.
   Button^ changeItemBtn;

   // This is the DataGridView control that displays the contents
   // of the list.
   DataGridView^ customersDataGridView;

   // This is the BindingSource used to bind the list to the
   // DataGridView control.
   BindingSource^ customersBindingSource;

public:
   Form1()
   {
      changeItemBtn = gcnew Button;
      customersDataGridView = gcnew DataGridView;
      customersBindingSource = gcnew BindingSource;

      // Set up the "Change Item" button.
            this->changeItemBtn->Text = L"Change Item";
      this->changeItemBtn->Dock = DockStyle::Bottom;
      this->changeItemBtn->Click += gcnew EventHandler(
         this, &Form1::changeItemBtn_Click );
      this->Controls->Add( this->changeItemBtn );
      
      // Set up the DataGridView.
      customersDataGridView->Dock = DockStyle::Top;
      this->Controls->Add( customersDataGridView );
      this->Size = System::Drawing::Size( 800, 200 );
      this->Load += gcnew EventHandler( this, &Form1::Form1_Load );
   }

private:
   void Form1_Load( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      // Create and populate the list of DemoCustomer objects
      // which will supply data to the DataGridView.
      List< DemoCustomer^ >^ customerList = gcnew List< DemoCustomer^ >;
      customerList->Add( DemoCustomer::CreateNewCustomer() );
      customerList->Add( DemoCustomer::CreateNewCustomer() );
      customerList->Add( DemoCustomer::CreateNewCustomer() );
      
      // Bind the list to the BindingSource.
      this->customersBindingSource->DataSource = customerList;
      
      // Attach the BindingSource to the DataGridView.
      this->customersDataGridView->DataSource =
         this->customersBindingSource;
   }

   // This event handler changes the value of the CompanyName
   // property for the first item in the list.
   void changeItemBtn_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      // Get a reference to the list from the BindingSource.
      List< DemoCustomer^ >^ customerList =
         static_cast<List< DemoCustomer^ >^>(
           this->customersBindingSource->DataSource);
      
      // Change the value of the CompanyName property for the
      // first item in the list.
      customerList->default[ 0 ]->CompanyName = L"Tailspin Toys";
      
      // Call ResetItem to alert the BindingSource that the
      // list has changed.
      this->customersBindingSource->ResetItem( 0 );
   }
};

int main()
{
   Application::EnableVisualStyles();
   Application::Run( gcnew Form1 );
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.Common;
using System.Diagnostics;
using System.Drawing;
using System.Data.SqlClient;
using System.Windows.Forms;

// This form demonstrates using a BindingSource to bind
// a list to a DataGridView control. The list does not
// raise change notifications, so the ResetItem method
// on the BindingSource is used.
public class Form1 : System.Windows.Forms.Form
{
    // This button causes the value of a list element to be changed.
    private Button changeItemBtn = new Button();

    // This is the DataGridView control that displays the contents
    // of the list.
    private DataGridView customersDataGridView = new DataGridView();

    // This is the BindingSource used to bind the list to the
    // DataGridView control.
    private BindingSource customersBindingSource = new BindingSource();

    public Form1()
    {
        // Set up the "Change Item" button.
        this.changeItemBtn.Text = "Change Item";
        this.changeItemBtn.Dock = DockStyle.Bottom;
        this.changeItemBtn.Click +=
            new EventHandler(changeItemBtn_Click);
        this.Controls.Add(this.changeItemBtn);

        // Set up the DataGridView.
        customersDataGridView.Dock = DockStyle.Top;
        this.Controls.Add(customersDataGridView);
        this.Size = new Size(800, 200);
        this.Load += new EventHandler(Form1_Load);
    }

    private void Form1_Load(System.Object sender, System.EventArgs e)
    {
        // Create and populate the list of DemoCustomer objects
        // which will supply data to the DataGridView.
        List<DemoCustomer> customerList = new List<DemoCustomer>();
        customerList.Add(DemoCustomer.CreateNewCustomer());
        customerList.Add(DemoCustomer.CreateNewCustomer());
        customerList.Add(DemoCustomer.CreateNewCustomer());

        // Bind the list to the BindingSource.
        this.customersBindingSource.DataSource = customerList;

        // Attach the BindingSource to the DataGridView.
        this.customersDataGridView.DataSource =
            this.customersBindingSource;
    }

    // This event handler changes the value of the CompanyName
    // property for the first item in the list.
    void changeItemBtn_Click(object sender, EventArgs e)
    {
        // Get a reference to the list from the BindingSource.
        List<DemoCustomer> customerList =
            this.customersBindingSource.DataSource as List<DemoCustomer>;

        // Change the value of the CompanyName property for the
        // first item in the list.
        customerList[0].CompanyName = "Tailspin Toys";

        // Call ResetItem to alert the BindingSource that the
        // list has changed.
        this.customersBindingSource.ResetItem(0);
    }

    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.Run(new Form1());
    }
}

// This class implements a simple customer type.
public class DemoCustomer
{
    // These fields hold the values for the public properties.
    private Guid idValue = Guid.NewGuid();
    private string customerName = String.Empty;
    private string companyNameValue = String.Empty;
    private string phoneNumberValue = String.Empty;

    // The constructor is private to enforce the factory pattern.
    private DemoCustomer()
    {
        customerName = "no data";
        companyNameValue = "no data";
        phoneNumberValue = "no data";
    }

    // This is the public factory method.
    public static DemoCustomer CreateNewCustomer()
    {
        return new DemoCustomer();
    }

    // This property represents an ID, suitable
    // for use as a primary key in a database.
    public Guid ID
    {
        get
        {
            return this.idValue;
        }
    }

    public string CompanyName
    {
        get
        {
            return this.companyNameValue;
        }

        set
        {
            this.companyNameValue = value;
        }
    }

    public string PhoneNumber
    {
        get
        {
            return this.phoneNumberValue;
        }

        set
        {
            this.phoneNumberValue = value;
        }
    }
}

Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Diagnostics
Imports System.Drawing
Imports System.Windows.Forms

' This form demonstrates using a BindingSource to bind
' a list to a DataGridView control. The list does not
' raise change notifications, so the ResetItem method 
' on the BindingSource is used.
Public Class Form1
    Inherits System.Windows.Forms.Form

    ' This button causes the value of a list element to be changed.
    Private WithEvents changeItemBtn As New Button()

    ' This is the DataGridView control that displays the contents 
    ' of the list.
    Private customersDataGridView As New DataGridView()

    ' This is the BindingSource used to bind the list to the 
    ' DataGridView control.
    Private WithEvents customersBindingSource As New BindingSource()

    Public Sub New()
        ' Set up the "Change Item" button.
        Me.changeItemBtn.Text = "Change Item"
        Me.changeItemBtn.Dock = DockStyle.Bottom
        Me.Controls.Add(Me.changeItemBtn)

        ' Set up the DataGridView.
        customersDataGridView.Dock = DockStyle.Top
        Me.Controls.Add(customersDataGridView)
        Me.Size = New Size(800, 200)
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles Me.Load
        ' Create and populate the list of DemoCustomer objects
        ' which will supply data to the DataGridView.
        Dim customerList As List(Of DemoCustomer) = _
        New List(Of DemoCustomer)
        customerList.Add(DemoCustomer.CreateNewCustomer())
        customerList.Add(DemoCustomer.CreateNewCustomer())
        customerList.Add(DemoCustomer.CreateNewCustomer())

        ' Bind the list to the BindingSource.
        Me.customersBindingSource.DataSource = customerList

        ' Attach the BindingSource to the DataGridView.
        Me.customersDataGridView.DataSource = Me.customersBindingSource
    End Sub

    ' This event handler changes the value of the CompanyName
    ' property for the first item in the list.
    Private Sub changeItemBtn_Click(ByVal sender As Object, ByVal e As EventArgs) _
       Handles changeItemBtn.Click

        ' Get a reference to the list from the BindingSource.
        Dim customerList As List(Of DemoCustomer) = _
        CType(Me.customersBindingSource.DataSource, List(Of DemoCustomer))

        ' Change the value of the CompanyName property for the 
        ' first item in the list.
        customerList(0).CompanyName = "Tailspin Toys"

        ' Call ResetItem to alert the BindingSource that the 
        ' list has changed.
        Me.customersBindingSource.ResetItem(0)

    End Sub

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

' This class implements a simple customer type.
Public Class DemoCustomer

    ' These fields hold the values for the public properties.
    Private idValue As Guid = Guid.NewGuid()
    Private customerName As String = String.Empty
    Private companyNameValue As String = String.Empty
    Private phoneNumberValue As String = String.Empty

    ' The constructor is private to enforce the factory pattern.
    Private Sub New()
        customerName = "no data"
        companyNameValue = "no data"
        phoneNumberValue = "no data"
    End Sub

    ' This is the public factory method.
    Public Shared Function CreateNewCustomer() As DemoCustomer
        Return New DemoCustomer()
    End Function

    ' This property represents an ID, suitable
    ' for use as a primary key in a database.
    Public ReadOnly Property ID() As Guid
        Get
            Return Me.idValue
        End Get
    End Property

    Public Property CompanyName() As String
        Get
            Return Me.companyNameValue
        End Get

        Set(ByVal value As String)
            Me.companyNameValue = Value
        End Set
    End Property


    Public Property PhoneNumber() As String
        Get
            Return Me.phoneNumberValue
        End Get

        Set(ByVal value As String)
            Me.phoneNumberValue = Value
        End Set
    End Property
End Class

Compiling the Code

This example requires:

References to the System, System.Data, System.Drawing and System.Windows.Forms assemblies.

Delen via

How to: Raise Change Notifications Using the BindingSource ResetItem Method

Example

Compiling the Code

See also

Aanvullende resources