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チュートリアル: Windows フォーム DataGridView コントロールでの仮想モードを実装する

非常に大量の表形式データを DataGridView コントロールに表示したい場合には、VirtualMode プロパティを true に設定し、コントロールとそのデータ ストアとの間のやり取りを明示的に管理することができます。 そうすることで、このような状況下においても、コントロールのパフォーマンスを最適に調整することができます。

DataGridView コントロールには、カスタム データ ストアとやり取りする際に処理できる、いくつかのイベントが用意されています。 このチュートリアルでは、それらのイベント ハンドラーを実装する手順について説明します。 このトピックのコード例では、説明をわかりやすくするために、非常にシンプルなデータ ソースを使用しています。 運用環境の設定では、通常、表示する必要のある行だけをキャッシュに読み込み、DataGridView イベントを処理してキャッシュとやり取りし、キャッシュを更新します。 詳細については、「Windows フォーム DataGridView コントロールでの Just-In-Time データ読み込みによる仮想モードの実装」を参照してください

このトピックのコードを単一のリストとしてコピーする方法については、「方法: Windows フォーム DataGridView コントロールで仮想モードを実装する」を参照してください。

フォームの作成

仮想モードを実装するには

  1. Form から派生し、DataGridView コントロールを含んだクラスを作成します。

    次のコードには、いくつかの基本的な初期化が含まれています。 このコードでは、後の手順で使用されるいくつかの変数を宣言し、Main メソッドを提供し、クラス コンストラクターでシンプルなフォーム レイアウトを提供しています。

    #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
    
  2. DataGridView コントロールを初期化し、データ ストアにサンプル値を設定する、フォームの Load イベントのハンドラーを実装します。

    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
    
  3. 要求されたセル値をデータ ストアまたは現在編集中の Customer オブジェクトから取得する、CellValueNeeded イベントのハンドラーを実装します。

    このイベントは、DataGridView コントロールでセルを塗りつぶす必要があるときに毎回発生します。

    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
    
  4. 編集された行を表す Customer オブジェクトに編集されたセル値を格納する、CellValuePushed イベントのハンドラーを実装します。 このイベントは、ユーザーがセル値の変更をコミットしたときに毎回発生します。

    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
    
  5. 新しく作成された行を表す新しい Customer オブジェクトを作成する、NewRowNeeded イベントのハンドラーを実装します。

    このイベントは、ユーザーが新しいレコードの行に移動したときに毎回発生します。

    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
    
  6. 新しい行または変更された行をデータ ストアに保存する、RowValidated イベントのハンドラーを実装します。

    このイベントは、ユーザーが現在の行を変更したときに毎回発生します。

    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
    
  7. Esc キーを編集モードで 2 回押すか、編集モード以外で 1 回押すことにより、ユーザーが行のバージョンの再設定を通知したときに、CancelRowEdit イベントを発生させるかどうかを示す、RowDirtyStateNeeded イベントのハンドラーを実装します。

    既定では、RowDirtyStateNeeded イベント ハンドラーで QuestionEventArgs.Response プロパティが true に設定されていない限り、現在の行のセルが変更されると、行のバージョンの再設定時に CancelRowEdit が発生します。 このイベントは、コミット スコープが実行時に決定される場合に役立ちます。

    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
    
  8. 現在の行を表す Customer オブジェクトの値を破棄する、CancelRowEdit イベントのハンドラーを実装します。

    このイベントは、Esc キーを編集モードでを 2 回押すか、編集モード以外で 1 回押すことによって、ユーザーが行のバージョン再設定を通知したときに発生します。 現在の行のセルが変更されていない場合や、RowDirtyStateNeeded イベント ハンドラーで QuestionEventArgs.Response プロパティの値が false に設定されている場合、このイベントは発生しません。

    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
    
  9. データ ストアから既存の Customer オブジェクトを削除するか、新しく作成された行を表す未保存の Customer オブジェクトを破棄する、UserDeletingRow イベントのハンドラーを実装します。

    このイベントは、ユーザーが行ヘッダーをクリックし、Delete キーを押して行を削除したときに毎回発生します。

    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
    
  10. このコード例で使用されているデータ項目を表す、シンプルな Customers クラスを実装します。

    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
    

アプリケーションのテスト

フォームをテストして、期待どおりに動作することを確認します。

フォームをテストするには

  • アプリケーションをコンパイルして実行します。

    3 つの顧客レコードが設定された DataGridView コントロールが表示されます。 行内の複数のセルの値を変更して、Esc キーを編集モードで 2 回押すか、編集モード以外で 1 回押すと、行全体を元の値に戻すことができます。 コントロール内の行を変更、追加、または削除すると、データ ストア内の Customer オブジェクトも変更、追加、または削除されます。

次の手順

このアプリケーションを使用すると、DataGridView コントロールに仮想モードを実装するために処理する必要があるイベントについて、基本的な理解を得ることができます。 この基本的なアプリケーションは、次のようなさまざまな方法で改善することもできます。

  • 外部データベースからの値をキャッシュするデータ ストアを実装する。 キャッシュでは、必要に応じて値を取得および破棄する必要があります。そうすることで、クライアント コンピューターでのメモリ消費を抑えながら、表示に必要なものだけを格納することができます。

  • 要件に応じて、データ ストアのパフォーマンスを微調整する。 たとえば、キャッシュ サイズを大きくしてデータベース クエリの数を最小限に抑えるようにすれば、クライアント コンピューターのメモリを制限することなく、低速なネットワーク接続による悪影響を緩和することができます。

外部データベースからの値のキャッシュについて詳しくは、「方法: Windows フォーム DataGridView コントロールで Just-In-Time データ読み込みを使用して仮想モードを実装する」を参照してください。

関連項目