Passo a passo: Implementando o modo virtual no controle DataGridView do Windows Forms

Quando você deseja exibir grandes quantidades de dados tabulares em um controle de DataGridView, você pode definir a propriedade VirtualMode para true e gerenciar explicitamente a interação do controle com seu armazenamento de dados. Isso permite ajustar o desempenho do controle nessa situação.

O controle DataGridView fornece vários eventos que você pode manipular para interagir com um armazenamento de dados personalizado. Este passo a passo orienta você pelo processo de implementação desses manipuladores de eventos. O exemplo de código neste tópico usa uma fonte de dados muito simples para fins de ilustração. Numa configuração de produção, normalmente carregará apenas as linhas que necessita de exibir num cache e irá manipular eventos DataGridView para interagir e atualizar o cache. Para obter mais informações, consulte Implementing Virtual Mode with Just-In-Time Data Loading in the Windows Forms DataGridView Control

Para copiar o código neste tópico como uma única listagem, consulte Como implementar o modo virtual no controle DataGridView do Windows Forms.

Criando o formulário

Para implementar o modo virtual

Crie uma classe que deriva de Form e contém um controle DataGridView.

O código a seguir contém algumas inicializações básicas. Ele declara algumas variáveis que serão usadas em etapas posteriores, fornece um método Main e fornece um layout de formulário simples no construtor de classe.

#using <System.Drawing.dll>
#using <System.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Windows::Forms;

public ref class Customer
{
private:
   String^ companyNameValue;
   String^ contactNameValue;

public:
   Customer()
   {
      
      // Leave fields empty.
   }

   Customer( String^ companyName, String^ contactName )
   {
      companyNameValue = companyName;
      contactNameValue = contactName;
   }


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

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

   }

   property String^ ContactName 
   {
      String^ get()
      {
         return contactNameValue;
      }

      void set( String^ value )
      {
         contactNameValue = value;
      }

   }

};

public ref class Form1: public Form
{
private:
   DataGridView^ dataGridView1;

   // Declare an ArrayList to serve as the data store. 
   System::Collections::ArrayList^ customers;

   // Declare a Customer object to store data for a row being edited.
   Customer^ customerInEdit;

   // Declare a variable to store the index of a row being edited. 
   // A value of -1 indicates that there is no row currently in edit. 
   int rowInEdit;

   // Declare a variable to indicate the commit scope. 
   // Set this value to false to use cell-level commit scope. 
   bool rowScopeCommit;

public:
   static void Main()
   {
      Application::Run( gcnew Form1 );
   }

   Form1()
   {
      dataGridView1 = gcnew DataGridView;
      customers = gcnew System::Collections::ArrayList;
      rowInEdit = -1;
      rowScopeCommit = true;
      
      // Initialize the form.
      this->dataGridView1->Dock = DockStyle::Fill;
      this->Controls->Add( this->dataGridView1 );
      this->Load += gcnew EventHandler( this, &Form1::Form1_Load );
   }

private:

using System;
using System.Windows.Forms;

public class Form1 : Form
{
    private DataGridView dataGridView1 = new DataGridView();

    // Declare an ArrayList to serve as the data store.
    private System.Collections.ArrayList customers =
        new System.Collections.ArrayList();

    // Declare a Customer object to store data for a row being edited.
    private Customer customerInEdit;

    // Declare a variable to store the index of a row being edited.
    // A value of -1 indicates that there is no row currently in edit.
    private int rowInEdit = -1;

    // Declare a variable to indicate the commit scope.
    // Set this value to false to use cell-level commit scope.
    private bool rowScopeCommit = true;

    [STAThreadAttribute()]
    public static void Main()
    {
        Application.Run(new Form1());
    }

    public Form1()
    {
        // Initialize the form.
        this.dataGridView1.Dock = DockStyle.Fill;
        this.Controls.Add(this.dataGridView1);
        this.Load += new EventHandler(Form1_Load);
        this.Text = "DataGridView virtual-mode demo (row-level commit scope)";
    }

Imports System.Windows.Forms

Public Class Form1
    Inherits Form

    Private WithEvents dataGridView1 As New DataGridView()

    ' Declare an ArrayList to serve as the data store. 
    Private customers As New System.Collections.ArrayList()

    ' Declare a Customer object to store data for a row being edited.
    Private customerInEdit As Customer

    ' Declare a variable to store the index of a row being edited. 
    ' A value of -1 indicates that there is no row currently in edit. 
    Private rowInEdit As Integer = -1

    ' Declare a variable to indicate the commit scope. 
    ' Set this value to false to use cell-level commit scope. 
    Private rowScopeCommit As Boolean = True

    <STAThreadAttribute()> _
    Public Shared Sub Main()
        Application.Run(New Form1())
    End Sub

    Public Sub New()
        ' Initialize the form.
        Me.dataGridView1.Dock = DockStyle.Fill
        Me.Controls.Add(Me.dataGridView1)
        Me.Text = "DataGridView virtual-mode demo (row-level commit scope)"
    End Sub

};

int main()
{
   Form1::Main();
}


End Class

Implemente um manipulador para o evento Load do formulário que inicializa o controle DataGridView e preenche o armazenamento de dados com valores de exemplo.

void Form1_Load( Object^ /*sender*/, EventArgs^ /*e*/ )
{
   
   // Enable virtual mode.
   this->dataGridView1->VirtualMode = true;
   
   // Connect the virtual-mode events to event handlers. 
   this->dataGridView1->CellValueNeeded += gcnew
       DataGridViewCellValueEventHandler( this, &Form1::dataGridView1_CellValueNeeded );
   this->dataGridView1->CellValuePushed += gcnew
       DataGridViewCellValueEventHandler( this, &Form1::dataGridView1_CellValuePushed );
   this->dataGridView1->NewRowNeeded += gcnew
       DataGridViewRowEventHandler( this, &Form1::dataGridView1_NewRowNeeded );
   this->dataGridView1->RowValidated += gcnew
       DataGridViewCellEventHandler( this, &Form1::dataGridView1_RowValidated );
   this->dataGridView1->RowDirtyStateNeeded += gcnew
       QuestionEventHandler( this, &Form1::dataGridView1_RowDirtyStateNeeded );
   this->dataGridView1->CancelRowEdit += gcnew
       QuestionEventHandler( this, &Form1::dataGridView1_CancelRowEdit );
   this->dataGridView1->UserDeletingRow += gcnew
       DataGridViewRowCancelEventHandler( this, &Form1::dataGridView1_UserDeletingRow );
   
   // Add columns to the DataGridView.
   DataGridViewTextBoxColumn^ companyNameColumn = gcnew DataGridViewTextBoxColumn;
   companyNameColumn->HeaderText = L"Company Name";
   companyNameColumn->Name = L"Company Name";
   DataGridViewTextBoxColumn^ contactNameColumn = gcnew DataGridViewTextBoxColumn;
   contactNameColumn->HeaderText = L"Contact Name";
   contactNameColumn->Name = L"Contact Name";
   this->dataGridView1->Columns->Add( companyNameColumn );
   this->dataGridView1->Columns->Add( contactNameColumn );
   this->dataGridView1->AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode::DisplayedCells;
   
   // Add some sample entries to the data store. 
   this->customers->Add( gcnew Customer( L"Bon app'",L"Laurence Lebihan" ) );
   this->customers->Add( gcnew Customer( L"Bottom-Dollar Markets",L"Elizabeth Lincoln" ) );
   this->customers->Add( gcnew Customer( L"B's Beverages",L"Victoria Ashworth" ) );
   
   // Set the row count, including the row for new records.
   this->dataGridView1->RowCount = 4;
}

private void Form1_Load(object sender, EventArgs e)
{
    // Enable virtual mode.
    this.dataGridView1.VirtualMode = true;

    // Connect the virtual-mode events to event handlers.
    this.dataGridView1.CellValueNeeded += new
        DataGridViewCellValueEventHandler(dataGridView1_CellValueNeeded);
    this.dataGridView1.CellValuePushed += new
        DataGridViewCellValueEventHandler(dataGridView1_CellValuePushed);
    this.dataGridView1.NewRowNeeded += new
        DataGridViewRowEventHandler(dataGridView1_NewRowNeeded);
    this.dataGridView1.RowValidated += new
        DataGridViewCellEventHandler(dataGridView1_RowValidated);
    this.dataGridView1.RowDirtyStateNeeded += new
        QuestionEventHandler(dataGridView1_RowDirtyStateNeeded);
    this.dataGridView1.CancelRowEdit += new
        QuestionEventHandler(dataGridView1_CancelRowEdit);
    this.dataGridView1.UserDeletingRow += new
        DataGridViewRowCancelEventHandler(dataGridView1_UserDeletingRow);

    // Add columns to the DataGridView.
    DataGridViewTextBoxColumn companyNameColumn = new
        DataGridViewTextBoxColumn();
    companyNameColumn.HeaderText = "Company Name";
    companyNameColumn.Name = "Company Name";
    DataGridViewTextBoxColumn contactNameColumn = new
        DataGridViewTextBoxColumn();
    contactNameColumn.HeaderText = "Contact Name";
    contactNameColumn.Name = "Contact Name";
    this.dataGridView1.Columns.Add(companyNameColumn);
    this.dataGridView1.Columns.Add(contactNameColumn);
    this.dataGridView1.AutoSizeColumnsMode =
        DataGridViewAutoSizeColumnsMode.DisplayedCells;

    // Add some sample entries to the data store.
    this.customers.Add(new Customer(
        "Bon app'", "Laurence Lebihan"));
    this.customers.Add(new Customer(
        "Bottom-Dollar Markets", "Elizabeth Lincoln"));
    this.customers.Add(new Customer(
        "B's Beverages", "Victoria Ashworth"));

    // Set the row count, including the row for new records.
    this.dataGridView1.RowCount = 4;
}

Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) _
    Handles Me.Load

    ' Enable virtual mode.
    Me.dataGridView1.VirtualMode = True

    ' Add columns to the DataGridView.
    Dim companyNameColumn As New DataGridViewTextBoxColumn()
    With companyNameColumn
        .HeaderText = "Company Name"
        .Name = "Company Name"
    End With
    Dim contactNameColumn As New DataGridViewTextBoxColumn()
    With contactNameColumn
        .HeaderText = "Contact Name"
        .Name = "Contact Name"
    End With
    Me.dataGridView1.Columns.Add(companyNameColumn)
    Me.dataGridView1.Columns.Add(contactNameColumn)
    Me.dataGridView1.AutoSizeColumnsMode = _
    DataGridViewAutoSizeColumnsMode.DisplayedCells

    ' Add some sample entries to the data store. 
    Me.customers.Add(New Customer("Bon app'", "Laurence Lebihan"))
    Me.customers.Add(New Customer("Bottom-Dollar Markets", _
        "Elizabeth Lincoln"))
    Me.customers.Add(New Customer("B's Beverages", "Victoria Ashworth"))

    ' Set the row count, including the row for new records.
    Me.dataGridView1.RowCount = 4

End Sub

Implemente um manipulador para o evento CellValueNeeded que recupera o valor da célula solicitada do armazenamento de dados ou do objeto Customer atualmente em edição.

Esse evento ocorre sempre que o controle DataGridView precisa pintar uma célula.

void dataGridView1_CellValueNeeded( Object^ /*sender*/,
    System::Windows::Forms::DataGridViewCellValueEventArgs^ e )
{
   Customer^ customerTmp = nullptr;
   
   // Store a reference to the Customer object for the row being painted.
   if ( e->RowIndex == rowInEdit )
   {
      customerTmp = this->customerInEdit;
   }
   else
   {
      customerTmp = dynamic_cast<Customer^>(this->customers[ e->RowIndex ]);
   }
   
   // Set the cell value to paint using the Customer object retrieved.
   int switchcase = 0;
   if ( (this->dataGridView1->Columns[ e->ColumnIndex ]->Name)->Equals( L"Company Name" ) )
         switchcase = 1;
   else
   if ( (this->dataGridView1->Columns[ e->ColumnIndex ]->Name)->Equals( L"Contact Name" ) )
         switchcase = 2;


   switch ( switchcase )
   {
      case 1:
         e->Value = customerTmp->CompanyName;
         break;

      case 2:
         e->Value = customerTmp->ContactName;
         break;
   }
}

private void dataGridView1_CellValueNeeded(object sender,
    System.Windows.Forms.DataGridViewCellValueEventArgs e)
{
    // If this is the row for new records, no values are needed.
    if (e.RowIndex == this.dataGridView1.RowCount - 1) return;

    Customer customerTmp = null;

    // Store a reference to the Customer object for the row being painted.
    if (e.RowIndex == rowInEdit)
    {
        customerTmp = this.customerInEdit;
    }
    else
    {
        customerTmp = (Customer)this.customers[e.RowIndex];
    }

    // Set the cell value to paint using the Customer object retrieved.
    switch (this.dataGridView1.Columns[e.ColumnIndex].Name)
    {
        case "Company Name":
            e.Value = customerTmp.CompanyName;
            break;

        case "Contact Name":
            e.Value = customerTmp.ContactName;
            break;
    }
}

Private Sub dataGridView1_CellValueNeeded(ByVal sender As Object, _
    ByVal e As System.Windows.Forms.DataGridViewCellValueEventArgs) _
    Handles dataGridView1.CellValueNeeded

    ' If this is the row for new records, no values are needed.
    If e.RowIndex = Me.dataGridView1.RowCount - 1 Then
        Return
    End If

    Dim customerTmp As Customer = Nothing

    ' Store a reference to the Customer object for the row being painted.
    If e.RowIndex = rowInEdit Then
        customerTmp = Me.customerInEdit
    Else
        customerTmp = CType(Me.customers(e.RowIndex), Customer)
    End If

    ' Set the cell value to paint using the Customer object retrieved.
    Select Case Me.dataGridView1.Columns(e.ColumnIndex).Name
        Case "Company Name"
            e.Value = customerTmp.CompanyName

        Case "Contact Name"
            e.Value = customerTmp.ContactName
    End Select

End Sub

Implemente um manipulador para o evento CellValuePushed que armazena um valor de célula editado no objeto Customer que representa a linha editada. Esse evento ocorre sempre que o usuário confirma uma alteração de valor de célula.

void dataGridView1_CellValuePushed( Object^ /*sender*/,
    System::Windows::Forms::DataGridViewCellValueEventArgs^ e )
{
   Customer^ customerTmp = nullptr;
   
   // Store a reference to the Customer object for the row being edited.
   if ( e->RowIndex < this->customers->Count )
   {
      
      // If the user is editing a new row, create a new Customer object.
      if ( this->customerInEdit == nullptr )
      {
         this->customerInEdit = gcnew Customer(
             (dynamic_cast<Customer^>(this->customers[ e->RowIndex ]))->CompanyName,
             (dynamic_cast<Customer^>(this->customers[ e->RowIndex ])->ContactName) );
      }

      customerTmp = this->customerInEdit;
      this->rowInEdit = e->RowIndex;
   }
   else
   {
      customerTmp = this->customerInEdit;
   }

   
   // Set the appropriate Customer property to the cell value entered.
   int switchcase = 0;
   if ( (this->dataGridView1->Columns[ e->ColumnIndex ]->Name)->Equals( L"Company Name" ) )
         switchcase = 1;
   else
   if ( (this->dataGridView1->Columns[ e->ColumnIndex ]->Name)->Equals( L"Contact Name" ) )
         switchcase = 2;


   switch ( switchcase )
   {
      case 1:
         customerTmp->CompanyName = dynamic_cast<String^>(e->Value);
         break;

      case 2:
         customerTmp->ContactName = dynamic_cast<String^>(e->Value);
         break;
   }
}

private void dataGridView1_CellValuePushed(object sender,
    System.Windows.Forms.DataGridViewCellValueEventArgs e)
{
    Customer customerTmp = null;

    // Store a reference to the Customer object for the row being edited.
    if (e.RowIndex < this.customers.Count)
    {
        // If the user is editing a new row, create a new Customer object.
        this.customerInEdit ??= new Customer(
            ((Customer)this.customers[e.RowIndex]).CompanyName,
            ((Customer)this.customers[e.RowIndex]).ContactName);
        customerTmp = this.customerInEdit;
        this.rowInEdit = e.RowIndex;
    }
    else
    {
        customerTmp = this.customerInEdit;
    }

    // Set the appropriate Customer property to the cell value entered.
    String newValue = e.Value as String;
    switch (this.dataGridView1.Columns[e.ColumnIndex].Name)
    {
        case "Company Name":
            customerTmp.CompanyName = newValue;
            break;

        case "Contact Name":
            customerTmp.ContactName = newValue;
            break;
    }
}

Private Sub dataGridView1_CellValuePushed(ByVal sender As Object, _
    ByVal e As System.Windows.Forms.DataGridViewCellValueEventArgs) _
    Handles dataGridView1.CellValuePushed

    Dim customerTmp As Customer = Nothing

    ' Store a reference to the Customer object for the row being edited.
    If e.RowIndex < Me.customers.Count Then

        ' If the user is editing a new row, create a new Customer object.
        If Me.customerInEdit Is Nothing Then
            Me.customerInEdit = New Customer( _
                CType(Me.customers(e.RowIndex), Customer).CompanyName, _
                CType(Me.customers(e.RowIndex), Customer).ContactName)
        End If
        customerTmp = Me.customerInEdit
        Me.rowInEdit = e.RowIndex

    Else
        customerTmp = Me.customerInEdit
    End If

    ' Set the appropriate Customer property to the cell value entered.
    Dim newValue As String = TryCast(e.Value, String)
    Select Case Me.dataGridView1.Columns(e.ColumnIndex).Name
        Case "Company Name"
            customerTmp.CompanyName = newValue
        Case "Contact Name"
            customerTmp.ContactName = newValue
    End Select

End Sub

Implemente um manipulador para o evento NewRowNeeded que cria um novo objeto Customer representando uma linha recém-criada.

Esse evento ocorre sempre que o usuário insere a linha para novos registros.

void dataGridView1_NewRowNeeded( Object^ /*sender*/,
    System::Windows::Forms::DataGridViewRowEventArgs^ /*e*/ )
{
   
   // Create a new Customer object when the user edits
   // the row for new records.
   this->customerInEdit = gcnew Customer;
   this->rowInEdit = this->dataGridView1->Rows->Count - 1;
}

private void dataGridView1_NewRowNeeded(object sender,
    System.Windows.Forms.DataGridViewRowEventArgs e)
{
    // Create a new Customer object when the user edits
    // the row for new records.
    this.customerInEdit = new Customer();
    this.rowInEdit = this.dataGridView1.Rows.Count - 1;
}

Private Sub dataGridView1_NewRowNeeded(ByVal sender As Object, _
    ByVal e As System.Windows.Forms.DataGridViewRowEventArgs) _
    Handles dataGridView1.NewRowNeeded

    ' Create a new Customer object when the user edits
    ' the row for new records.
    Me.customerInEdit = New Customer()
    Me.rowInEdit = Me.dataGridView1.Rows.Count - 1

End Sub

Implemente um manipulador para o evento RowValidated que salva linhas novas ou modificadas no armazenamento de dados.

Esse evento ocorre sempre que o usuário altera a linha atual.

void dataGridView1_RowValidated( Object^ /*sender*/,
    System::Windows::Forms::DataGridViewCellEventArgs^ e )
{
   
   // Save row changes if any were made and release the edited 
   // Customer object if there is one.
   if ( e->RowIndex >= this->customers->Count && e->RowIndex != this->dataGridView1->Rows->Count - 1 )
   {
      
      // Add the new Customer object to the data store.
      this->customers->Add( this->customerInEdit );
      this->customerInEdit = nullptr;
      this->rowInEdit = -1;
   }
   else
   if ( this->customerInEdit != nullptr && e->RowIndex < this->customers->Count )
   {
      
      // Save the modified Customer object in the data store.
      this->customers[ e->RowIndex ] = this->customerInEdit;
      this->customerInEdit = nullptr;
      this->rowInEdit = -1;
   }
   else
   if ( this->dataGridView1->ContainsFocus )
   {
      this->customerInEdit = nullptr;
      this->rowInEdit = -1;
   }
}

private void dataGridView1_RowValidated(object sender,
    System.Windows.Forms.DataGridViewCellEventArgs e)
{
    // Save row changes if any were made and release the edited
    // Customer object if there is one.
    if (e.RowIndex >= this.customers.Count &&
        e.RowIndex != this.dataGridView1.Rows.Count - 1)
    {
        // Add the new Customer object to the data store.
        this.customers.Add(this.customerInEdit);
        this.customerInEdit = null;
        this.rowInEdit = -1;
    }
    else if (this.customerInEdit != null &&
        e.RowIndex < this.customers.Count)
    {
        // Save the modified Customer object in the data store.
        this.customers[e.RowIndex] = this.customerInEdit;
        this.customerInEdit = null;
        this.rowInEdit = -1;
    }
    else if (this.dataGridView1.ContainsFocus)
    {
        this.customerInEdit = null;
        this.rowInEdit = -1;
    }
}

Private Sub dataGridView1_RowValidated(ByVal sender As Object, _
    ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) _
    Handles dataGridView1.RowValidated

    ' Save row changes if any were made and release the edited 
    ' Customer object if there is one.
    If e.RowIndex >= Me.customers.Count AndAlso _
        e.RowIndex <> Me.dataGridView1.Rows.Count - 1 Then

        ' Add the new Customer object to the data store.
        Me.customers.Add(Me.customerInEdit)
        Me.customerInEdit = Nothing
        Me.rowInEdit = -1

    ElseIf (Me.customerInEdit IsNot Nothing) AndAlso _
        e.RowIndex < Me.customers.Count Then

        ' Save the modified Customer object in the data store.
        Me.customers(e.RowIndex) = Me.customerInEdit
        Me.customerInEdit = Nothing
        Me.rowInEdit = -1

    ElseIf Me.dataGridView1.ContainsFocus Then

        Me.customerInEdit = Nothing
        Me.rowInEdit = -1

    End If

End Sub

Implemente um manipulador para o evento RowDirtyStateNeeded que indique se o evento CancelRowEdit ocorrerá quando o usuário sinalizar a reversão da linha pressionando ESC duas vezes no modo de edição ou uma vez fora do modo de edição.

Por padrão, CancelRowEdit ocorre após a reversão da linha quando quaisquer células na linha atual foram modificadas, a menos que a propriedade QuestionEventArgs.Response esteja definida como true no manipulador de eventos RowDirtyStateNeeded. Esse evento é útil quando o escopo de confirmação é determinado em tempo de execução.

void dataGridView1_RowDirtyStateNeeded( Object^ /*sender*/,
    System::Windows::Forms::QuestionEventArgs^ e )
{
   if (  !rowScopeCommit )
   {
      
      // In cell-level commit scope, indicate whether the value
      // of the current cell has been modified.
      e->Response = this->dataGridView1->IsCurrentCellDirty;
   }
}

private void dataGridView1_RowDirtyStateNeeded(object sender,
    System.Windows.Forms.QuestionEventArgs e)
{
    if (!rowScopeCommit)
    {
        // In cell-level commit scope, indicate whether the value
        // of the current cell has been modified.
        e.Response = this.dataGridView1.IsCurrentCellDirty;
    }
}

Private Sub dataGridView1_RowDirtyStateNeeded(ByVal sender As Object, _
    ByVal e As System.Windows.Forms.QuestionEventArgs) _
    Handles dataGridView1.RowDirtyStateNeeded

    If Not rowScopeCommit Then

        ' In cell-level commit scope, indicate whether the value
        ' of the current cell has been modified.
        e.Response = Me.dataGridView1.IsCurrentCellDirty

    End If

End Sub

Implemente um manipulador para o evento CancelRowEdit que descarta os valores do objeto Customer que representa a linha atual.

Esse evento ocorre quando o usuário sinaliza a reversão da linha pressionando ESC duas vezes no modo de edição ou uma vez fora do modo de edição. Esse evento não ocorrerá se nenhuma célula na linha atual tiver sido modificada ou se o valor da propriedade QuestionEventArgs.Response tiver sido definido como false em um manipulador de eventos RowDirtyStateNeeded.

void dataGridView1_CancelRowEdit( Object^ /*sender*/,
    System::Windows::Forms::QuestionEventArgs^ /*e*/ )
{
   if ( this->rowInEdit == this->dataGridView1->Rows->Count - 2 &&
        this->rowInEdit == this->customers->Count )
   {
      
      // If the user has canceled the edit of a newly created row, 
      // replace the corresponding Customer object with a new, empty one.
      this->customerInEdit = gcnew Customer;
   }
   else
   {
      
      // If the user has canceled the edit of an existing row, 
      // release the corresponding Customer object.
      this->customerInEdit = nullptr;
      this->rowInEdit = -1;
   }
}

private void dataGridView1_CancelRowEdit(object sender,
    System.Windows.Forms.QuestionEventArgs e)
{
    if (this.rowInEdit == this.dataGridView1.Rows.Count - 2 &&
        this.rowInEdit == this.customers.Count)
    {
        // If the user has canceled the edit of a newly created row,
        // replace the corresponding Customer object with a new, empty one.
        this.customerInEdit = new Customer();
    }
    else
    {
        // If the user has canceled the edit of an existing row,
        // release the corresponding Customer object.
        this.customerInEdit = null;
        this.rowInEdit = -1;
    }
}

Private Sub dataGridView1_CancelRowEdit(ByVal sender As Object, _
    ByVal e As System.Windows.Forms.QuestionEventArgs) _
    Handles dataGridView1.CancelRowEdit

    If Me.rowInEdit = Me.dataGridView1.Rows.Count - 2 AndAlso _
        Me.rowInEdit = Me.customers.Count Then

        ' If the user has canceled the edit of a newly created row, 
        ' replace the corresponding Customer object with a new, empty one.
        Me.customerInEdit = New Customer()

    Else

        ' If the user has canceled the edit of an existing row, 
        ' release the corresponding Customer object.
        Me.customerInEdit = Nothing
        Me.rowInEdit = -1

    End If

End Sub

Implemente um manipulador para o evento UserDeletingRow que exclui um objeto Customer existente do armazenamento de dados ou descarta um objeto Customer não salvo que representa uma linha recém-criada.

Esse evento ocorre sempre que o usuário exclui uma linha clicando em um cabeçalho de linha e pressionando a tecla DELETE.

void dataGridView1_UserDeletingRow( Object^ /*sender*/,
    System::Windows::Forms::DataGridViewRowCancelEventArgs^ e )
{
   if ( e->Row->Index < this->customers->Count )
   {
      
      // If the user has deleted an existing row, remove the 
      // corresponding Customer object from the data store.
      this->customers->RemoveAt( e->Row->Index );
   }

   if ( e->Row->Index == this->rowInEdit )
   {
      
      // If the user has deleted a newly created row, release
      // the corresponding Customer object. 
      this->rowInEdit = -1;
      this->customerInEdit = nullptr;
   }
}

private void dataGridView1_UserDeletingRow(object sender,
    System.Windows.Forms.DataGridViewRowCancelEventArgs e)
{
    if (e.Row.Index < this.customers.Count)
    {
        // If the user has deleted an existing row, remove the
        // corresponding Customer object from the data store.
        this.customers.RemoveAt(e.Row.Index);
    }

    if (e.Row.Index == this.rowInEdit)
    {
        // If the user has deleted a newly created row, release
        // the corresponding Customer object.
        this.rowInEdit = -1;
        this.customerInEdit = null;
    }
}

Private Sub dataGridView1_UserDeletingRow(ByVal sender As Object, _
    ByVal e As System.Windows.Forms.DataGridViewRowCancelEventArgs) _
    Handles dataGridView1.UserDeletingRow

    If e.Row.Index < Me.customers.Count Then

        ' If the user has deleted an existing row, remove the 
        ' corresponding Customer object from the data store.
        Me.customers.RemoveAt(e.Row.Index)

    End If

    If e.Row.Index = Me.rowInEdit Then

        ' If the user has deleted a newly created row, release
        ' the corresponding Customer object. 
        Me.rowInEdit = -1
        Me.customerInEdit = Nothing

    End If

End Sub

Implemente uma classe Customers simples para representar os itens de dados usados por este exemplo de código.

public ref class Customer
{
private:
   String^ companyNameValue;
   String^ contactNameValue;

public:
   Customer()
   {
      
      // Leave fields empty.
   }

   Customer( String^ companyName, String^ contactName )
   {
      companyNameValue = companyName;
      contactNameValue = contactName;
   }


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

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

   }

   property String^ ContactName 
   {
      String^ get()
      {
         return contactNameValue;
      }

      void set( String^ value )
      {
         contactNameValue = value;
      }

   }

};

public class Customer
{
    private String companyNameValue;
    private String contactNameValue;

    public Customer()
    {
        // Leave fields empty.
    }

    public Customer(String companyName, String contactName)
    {
        companyNameValue = companyName;
        contactNameValue = contactName;
    }

    public String CompanyName
    {
        get
        {
            return companyNameValue;
        }
        set
        {
            companyNameValue = value;
        }
    }

    public String ContactName
    {
        get
        {
            return contactNameValue;
        }
        set
        {
            contactNameValue = value;
        }
    }
}

Public Class Customer

    Private companyNameValue As String
    Private contactNameValue As String

    Public Sub New()
        ' Leave fields empty.
    End Sub

    Public Sub New(ByVal companyName As String, ByVal contactName As String)
        companyNameValue = companyName
        contactNameValue = contactName
    End Sub

    Public Property CompanyName() As String
        Get
            Return companyNameValue
        End Get
        Set(ByVal value As String)
            companyNameValue = value
        End Set
    End Property

    Public Property ContactName() As String
        Get
            Return contactNameValue
        End Get
        Set(ByVal value As String)
            contactNameValue = value
        End Set
    End Property

End Class

Testando o aplicativo

Agora você pode testar o formulário para garantir que ele se comporte conforme o esperado.

Para testar o formulário

Compile e execute o aplicativo.

Verá um controlo DataGridView preenchido com três registos de clientes. Você pode modificar os valores de várias células em uma linha e pressionar ESC duas vezes no modo de edição e uma vez fora do modo de edição para reverter toda a linha para seus valores originais. Quando você modifica, adiciona ou exclui linhas no controle, Customer objetos no armazenamento de dados também são modificados, adicionados ou excluídos.

Próximas Etapas

Este aplicativo fornece uma compreensão básica dos eventos que você deve manipular para implementar o modo virtual no controle DataGridView. Você pode melhorar esse aplicativo básico de várias maneiras:

Implemente um armazenamento de dados que armazene em cache valores de um banco de dados externo. O cache deve recuperar e descartar valores conforme necessário para que contenha apenas o necessário para exibição enquanto consome uma pequena quantidade de memória no computador cliente.
Ajuste o desempenho do armazenamento de dados dependendo de suas necessidades. Por exemplo, talvez você queira compensar conexões de rede lentas em vez de limitações de memória cliente-computador usando um tamanho de cache maior e minimizando o número de consultas de banco de dados.

Para obter mais informações sobre como armazenar valores em cache de um banco de dados externo, consulte Como implementar o modo virtual com carregamento de dados just-In-Time no controle DataGridView do Windows Forms.

Ver também

DataGridView
VirtualMode
CellValueNeeded
CellValuePushed
NewRowNeeded
RowValidated
RowDirtyStateNeeded
CancelRowEdit
UserDeletingRow
Otimização de Desempenho no controlo DataGridView do Windows Forms
Práticas recomendadas para escalonar o controlo DataGridView do Windows Forms
Implementando o modo virtual comIn-Time apenas carregamento de dados no controlo DataGridView do Windows Forms
Como: Implementar o modo virtual no de controle DataGridView do Windows Forms

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Last updated on 2025-05-07