Exemplarische Vorgehensweise: Implementieren des virtuellen Modus im DataGridView-Steuerelement in Windows Forms

Artikel
08/10/2011

Wenn Sie sehr umfangreiche Tabellendaten in einem DataGridView-Steuerelement anzeigen möchten, können Sie die VirtualMode-Eigenschaft auf true festlegen und die Interaktion des Steuerelements mit dem Datenspeicher explizit verwalten. Auf diese Weise können Sie die Leistung des Steuerelements in dieser Situation feiner abstimmen.

Das DataGridView-Steuerelement stellt mehrere Ereignisse bereit, die Sie für die Interaktion mit einem benutzerdefinierten Datenspeicher behandeln können. Diese exemplarische Vorgehensweise führt Sie durch die Schritte zum Implementieren dieser Ereignishandler. Im Codebeispiel in diesem Thema wird eine sehr einfache Datenquelle zu Illustrationszwecken verwendet. In einer Produktionsumgebung werden normalerweise nur die anzuzeigenden Zeilen in einen Cache geladen und DataGridView-Ereignisse behandelt, um mit dem Cache zu interagieren und diesen zu aktualisieren. Weitere Informationen finden Sie unter Implementieren des virtuellen Modus mit Just-In-Time-Laden von Daten in das DataGridView-Steuerelement in Windows Forms.

Informationen zum Kopieren des Codes in diesem Thema als einzelne Auflistung finden Sie unter Gewusst wie: Implementieren des virtuellen Modus im DataGridView-Steuerelement in Windows Forms.

Erstellen des Formulars

So implementieren Sie den virtuellen Modus

Erstellen Sie eine Klasse, die von Form abgeleitet wird und ein DataGridView-Steuerelement enthält.

Der folgende Code enthält einigen Code für die grundlegende Initialisierung. In der Initialisierung werden einige Variablen deklariert, die in nachfolgenden Schritten verwendet werden. Außerdem wird eine Main-Methode sowie das Layout für ein einfaches Formular im Klassenkonstruktor bereitgestellt.

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();
}

Implementieren Sie einen Handler für das Load-Ereignis des Formulars, durch den das DataGridView-Steuerelement initialisiert und der Datenspeicher mit Beispieldaten gefüllt wird.

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;
   }

Implementieren Sie einen Handler für das CellValueNeeded-Ereignis, durch den der angeforderte Zellwert vom Datenspeicher oder vom derzeit bearbeiteten Customer-Objekt abgerufen wird.

Dieses Ereignis tritt ein, wenn eine Zelle vom DataGridView-Steuerelement gezeichnet werden muss.

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;
      }
   }

Implementieren Sie einen Handler für das CellValuePushed-Ereignis, durch den ein bearbeiteter Zellwert im Customer-Objekt gespeichert wird, das die bearbeitete Zeile darstellt. Dieses Ereignis tritt ein, wenn der Benutzer für einen geänderten Zellwert einen Commit ausführt.

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;
      }
   }

Implementieren Sie einen Handler für das NewRowNeeded-Ereignis, durch den ein neues Customer-Objekt erstellt wird, das eine neu erstellte Zeile darstellt.

Dieses Ereignis tritt ein, wenn der Benutzer in die Zeile für neue Datensätze klickt.

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;
   }

Implementieren Sie einen Handler für das RowValidated-Ereignis, durch den neue oder geänderte Zeilen im Datenspeicher gespeichert werden.

Dieses Ereignis tritt ein, wenn der Benutzer die aktuelle Zeile ändert.

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;
      }
   }

Implementieren Sie einen Handler für das RowDirtyStateNeeded-Ereignis, durch den angegeben wird, ob das CancelRowEdit-Ereignis auftritt, sobald der Benutzer das Zurücksetzen einer Zeile signalisiert, indem er im Bearbeitungsmodus zweimal oder außerhalb des Bearbeitungsmodus einmal die ESC-TASTE drückt.

CancelRowEdit tritt beim Zurücksetzen von Zeilen standardmäßig ein, wenn Zellen in der aktuellen Zeile geändert wurden. Wenn die QuestionEventArgs.Response-Eigenschaft im RowDirtyStateNeeded-Ereignishandler auf true festgelegt wurde, gilt dies allerdings nicht. Dieses Ereignis ist hilfreich, wenn der Commit-Bereich zur Laufzeit bestimmt wird.

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;
      }
   }

Implementieren Sie einen Handler für das CancelRowEdit-Ereignis, durch den die Werte des Customer-Objekts verworfen werden, das die aktuelle Zeile darstellt.

Dieses Ereignis tritt ein, sobald der Benutzer das Zurücksetzen einer Zeile signalisiert, indem er im Bearbeitungsmodus zweimal oder außerhalb des Bearbeitungsmodus einmal die ESC-TASTE drückt. Das Ereignis tritt nicht ein, wenn in der aktuellen Zeile keine Zellen geändert wurden oder der Wert der QuestionEventArgs.Response-Eigenschaft in einem RowDirtyStateNeeded-Ereignishandler auf false festgelegt wurde.

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;
      }
   }

Implementieren Sie einen Handler für das UserDeletingRow-Ereignis, durch den ein vorhandenes Customer-Objekt aus dem Datenspeicher gelöscht oder ein nicht gespeichertes Customer-Objekt verworfen wird, das eine neu erstellte Zeile darstellt.

Dieses Ereignis tritt ein, wenn der Benutzer eine Zeile löscht, indem er auf einen Zeilenheader klickt und die ENTF-TASTE drückt.

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;
   }
}

Implementieren Sie eine einfache Customers-Klasse, um die von diesem Codebeispiel verwendeten Datenelemente darzustellen.

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;
      }

   }

};

Testen der Anwendung

Sie können das Formular jetzt testen und prüfen, ob es sich wie erwartet verhält.

So testen Sie das Formular

Kompilieren Sie die Anwendung, und führen Sie sie aus.

Sie sehen ein mit drei Kundendatensätzen gefülltes DataGridView-Steuerelement. Sie können die Werte mehrerer Zellen in einer Zeile ändern und im Bearbeitungsmodus zweimal sowie außerhalb des Bearbeitungsmodus einmal die ESC-Taste drücken, um die gesamte Zeile wieder auf die ursprünglichen Werte zurückzusetzen. Beim Ändern, Hinzufügen oder Löschen von Zeilen im Steuerelement werden ebenfalls die Customer-Objekte im Datenspeicher geändert, hinzugefügt oder gelöscht.

Nächste Schritte

Diese Anwendung vermittelt grundlegende Kenntnisse zu den Ereignissen, die zur Implementierung des virtuellen Modus im DataGridView-Steuerelement behandelt werden müssen. Sie können diese Basisanwendung auf vielfältige Weise verbessern:

Implementieren Sie einen Datenspeicher, der Werte von einer externen Datenbank zwischenspeichert. Der Cache sollte Werte ggf. abrufen und verwerfen, sodass er nur die Daten enthält, die für die Anzeige erforderlich sind, und möglichst wenig Speicherplatz auf dem Clientcomputer belegt.
Sie sollten die Leistung des Datenspeichers optimal an Ihre Anforderungen anpassen. Beispielsweise können Sie langsame Netzwerkverbindungen kompensieren, indem Sie eine höhere Cachekapazität verwenden und die Anzahl der Datenbankabfragen reduzieren. Speicherbeschränkungen auf dem Clientcomputer bleiben dabei jedoch unberücksichtigt.

Weitere Informationen zum Zwischenspeichern von Werten von einer externen Datenbank finden Sie unter Gewusst wie: Implementieren des virtuellen Modus mit Just-In-Time-Laden von Daten in das DataGridView-Steuerelement in Windows Forms.

Siehe auch

Freigeben über

Exemplarische Vorgehensweise: Implementieren des virtuellen Modus im DataGridView-Steuerelement in Windows Forms

Erstellen des Formulars

So implementieren Sie den virtuellen Modus

Testen der Anwendung

So testen Sie das Formular

Nächste Schritte

Siehe auch

Aufgaben

Referenz

Konzepte

Weitere Ressourcen

Zusätzliche Ressourcen