Tutorial: Implementar el modo virtual en el control DataGridView de formularios Windows Forms

Artículo
08/10/2011

Si desea mostrar grandes volúmenes de datos en formato de tabla en un control DataGridView, puede establecer la propiedad VirtualMode en true y administrar de forma explícita la interacción del control con el almacén de datos. Esto le permite ajustar el rendimiento del control en esta situación.

El control DataGridView proporciona varios eventos que puede controlar para interactuar con un almacén de datos personalizado. Este tutorial le guía a través del proceso de implementar estos controladores de eventos. En el ejemplo de código de este tema se utiliza un origen de datos muy sencillo para fines de ilustración. En una configuración de producción, normalmente cargará sólo las filas que necesite mostrar en caché y controlará eventos DataGridView para interactuar con la caché y actualizarla. Para obtener más información, vea Implementar el modo virtual mediante la carga de datos Just-In-Time en el control DataGridView de formularios Windows Forms.

Para copiar el código de este tema como un listado sencillo, vea Cómo: Implementar el modo virtual en el control DataGridView de formularios Windows Forms.

Crear el formulario

Para implementar el modo virtual

Cree una clase que deriva de Form y contiene un control DataGridView.

El código siguiente contiene alguna inicialización básica. Se declaran algunas variables que se utilizarán en pasos posteriores, se proporciona un método Main y un diseño de formulario sencillo del constructor de clase.

Imports System
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


...



End Class

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)";
    }


...


}

#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:


...


};

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

Implemente un controlador para el evento Load del formulario que inicializa el control DataGridView y rellena el almacén de datos con valores de ejemplo.

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.AllCells

    ' 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

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.AllCells;

    // 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;
}

   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::AllCells;

      // 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;
   }

Implemente un controlador para el evento CellValueNeeded que recupera el valor de celda solicitado del almacén de datos o el objeto Customer actualmente en edición.

Este evento aparece cada vez que el control DataGridView tiene que dibujar una celda.

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

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;
    }
}

   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;
      }
   }

Implemente un controlador para el evento CellValuePushed que almacena un valor de celda editado en el objeto Customer que representa la fila editada. Este evento se produce cada vez que el usuario confirma un cambio de valor de celda.

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

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.
        if (this.customerInEdit == null)
        {
            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;
    }
}

   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;
      }
   }

Implemente un controlador para el evento NewRowNeeded que crea un nuevo objeto Customer que representa una fila recién creada.

Este evento aparece cada vez que el usuario especifica la fila de nuevos registros.

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

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;
}

   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;
   }

Implemente un controlador para el evento RowValidated que guarda las filas nuevas o modificadas en el almacén de datos.

Este evento aparece cada vez que el usuario cambia la fila actual.

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

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;
    }
}

   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;
      }
   }

Implemente un controlador para el evento RowDirtyStateNeeded que indica si se producirá el evento CancelRowEdit cuando el usuario señale la inversión de fila presionando dos veces ESC en el modo de edición o una vez fuera del modo de edición.

De forma predeterminada, se produce el evento CancelRowEdit con la inversión de fila cuando se ha modificado alguna celda de la fila actual, a no ser que la propiedad QuestionEventArgs.Response esté establecida en true en el controlador de eventos RowDirtyStateNeeded. Este evento resulta de utilidad cuando se determina el ámbito de la confirmación en tiempo de ejecución.

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

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;
    }
}

   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;
      }
   }

Implemente un controlador para el evento CancelRowEdit que descarta los valores del objeto Customer que representa la fila actual.

Se produce este evento cuando el usuario señala la reversión de la fila presionando dos veces ESC en modo de edición o una vez fuera del modo de edición. No se produce este evento si no se ha modificado ninguna celda de la fila actual o si se ha establecido el valor de la propiedad QuestionEventArgs.Response en false en un controlador de eventos RowDirtyStateNeeded.

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

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;
    }
}

   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;
      }
   }

Implemente un controlador para el evento UserDeletingRow que elimina un objeto Customer existente del almacén de datos o descarta un objeto Customer no guardado que representa una fila recién creada.

Se produce este evento siempre que el usuario elimina una fila haciendo clic en un encabezado de fila y presionando la tecla SUPR.

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

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;
    }
}

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;
   }
}

Implemente una clase Customers simple para representar los elementos de datos utilizados por este ejemplo de código.

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

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 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;
      }

   }

};

Probar la aplicación

Puede comprobar el formulario para asegurarse de que se comporta de la forma prevista.

Para comprobar el formulario

Compile y ejecute la aplicación.

Aparecerá un control DataGridView rellenado con tres registros del cliente. Puede modificar los valores de varias celdas de una fila y presionar dos veces ESC en el modo de edición y una vez fuera de éste modo para invertir la fila completa a sus valores originales. Cuando modifica, agrega o elimina filas del control, se modifican, agregan o eliminan objetos Customer del almacén de datos, también.

Pasos siguientes

Esta aplicación proporciona conocimientos básicos de los eventos que debe controlar para implementar el modo virtual en el control DataGridView. Puede mejorar esta aplicación básica de varios maneras:

Implemente un almacén de datos que almacena en memoria caché los valores de una base de datos externa. La caché recuperará y descartará valores según sea necesario de modo que sólo contenga lo que es necesario para la presentación a la vez que utiliza una pequeña cantidad de memoria en el equipo cliente.
Ajuste el rendimiento del almacén de datos en función de sus requisitos. Por ejemplo, quizá desee compensar las conexiones de red ralentizadas en lugar de las limitaciones de memoria del equipo cliente utilizando un tamaño mayor de caché y minimizando el número de consultas de base de datos.

Para obtener más información sobre cómo almacenar en memoria caché valores de una base de datos externa, vea Cómo: Implementar el modo virtual con la carga de datos Just-In-Time en el control DataGridView de formularios Windows Forms.

Vea también

Tutorial: Implementar el modo virtual en el control DataGridView de formularios Windows Forms

Crear el formulario

Para implementar el modo virtual

Probar la aplicación

Para comprobar el formulario

Pasos siguientes

Vea también

Tareas

Referencia

Conceptos

Otros recursos

Recursos adicionales