方法: 子テーブルで選択した行が正しい位置に残っていることを確認する

Windows フォームでデータ バインディングを操作する場合、多くの場合、親/子ビューまたはマスター/詳細ビューと呼ばれるものにデータが表示されます。 これは、同じソースのデータが 2 つのコントロールに表示されるデータ バインディング シナリオを指します。 1 つのコントロールで選択を変更すると、2 番目のコントロールに表示されるデータが変更されます。 たとえば、1 つ目のコントロールには顧客のリストが含まれており、2 番目のコントロールには、選択した顧客に関連する注文の一覧が含まれている場合があります。

.NET Framework バージョン 2.0 以降では、親/子ビューにデータを表示するときに、子テーブルで現在選択されている行がテーブルの最初の行にリセットされないようにするための追加の手順を実行する必要がある場合があります。 これを行うには、子テーブルの位置をキャッシュし、親テーブルの変更後にリセットする必要があります。 通常、子リセットは、親テーブルの行のフィールドが初めて変更された場合に発生します。

現在の子位置をキャッシュするには

1. 子リストの位置を格納する整数変数と、子の位置をキャッシュするかどうかを格納するブール変数を宣言します。

   private int cachedPosition = -1;
   private bool cacheChildPosition = true;
   

   Private cachedPosition As Integer = - 1
   Private cacheChildPosition As Boolean = True
   
   

2. バインディングの CurrencyManager の ListChanged イベントを処理し、Resetの ListChangedType を確認します。

3. CurrencyManagerの現在位置を確認します。 リストの最初のエントリ (通常は 0) より大きい場合は、変数に保存します。

   void relatedCM_ListChanged(object sender, ListChangedEventArgs e)
   {
       // Check to see if this is a caching situation.
       if (cacheChildPosition && cachePositionCheckBox.Checked)
       {
           // If so, check to see if it is a reset situation, and the current
           // position is greater than zero.
           CurrencyManager relatedCM = sender as CurrencyManager;
           if (e.ListChangedType == ListChangedType.Reset && relatedCM.Position > 0)
   
               // If so, cache the position of the child table.
               cachedPosition = relatedCM.Position;
       }
   }
   

   Private Sub relatedCM_ListChanged(ByVal sender As Object, _
       ByVal e As ListChangedEventArgs)
       ' Check to see if this is a caching situation.
       If cacheChildPosition AndAlso cachePositionCheckBox.Checked Then
           ' If so, check to see if it is a reset situation, and the current
           ' position is greater than zero.
           Dim relatedCM As CurrencyManager = sender
           If e.ListChangedType = ListChangedType.Reset _
               AndAlso relatedCM.Position > 0 Then
   
               ' If so, cache the position of the child table.
               cachedPosition = relatedCM.Position
           End If
       End If
   
   End Sub
   

4. 親通貨マネージャーの親リストの CurrentChanged イベントを処理します。 ハンドラーで、キャッシュ シナリオではないことを示すブール値を設定します。 CurrentChanged が発生した場合、親への変更はリスト位置の変更であり、項目値の変更ではありません。

   void bindingSource1_CurrentChanged(object sender, EventArgs e)
   {
       // If the CurrentChanged event occurs, this is not a caching
       // situation.
       cacheChildPosition = false;
   }
   

   ' Handle the current changed event. This event occurs when
   ' the current item is changed, but not when a field of the current
   ' item is changed.
   Private Sub bindingSource1_CurrentChanged(ByVal sender As Object, _
       ByVal e As EventArgs) Handles bindingSource1.CurrentChanged
       ' If the CurrentChanged event occurs, this is not a caching 
       ' situation.
       cacheChildPosition = False
   
   End Sub
   

子の位置をリセットするには

1. PositionChanged イベントを子バインディングの CurrencyManagerに対して処理します。

2. 子テーブルの位置を、前の手順で保存したキャッシュされた位置にリセットします。

   void relatedCM_PositionChanged(object sender, EventArgs e)
   {
       // Check to see if this is a caching situation.
       if (cacheChildPosition && cachePositionCheckBox.Checked)
       {
           CurrencyManager relatedCM = sender as CurrencyManager;
   
           // If so, check to see if the current position is
           // not equal to the cached position and the cached
           // position is not out of bounds.
           if (relatedCM.Position != cachedPosition && cachedPosition
               > 0 && cachedPosition < relatedCM.Count)
           {
               relatedCM.Position = cachedPosition;
               cachedPosition = -1;
           }
       }
   }
   

   Private Sub relatedCM_PositionChanged(ByVal sender As Object, ByVal e As EventArgs) 
       ' Check to see if this is a caching situation.
       If cacheChildPosition AndAlso cachePositionCheckBox.Checked Then
           Dim relatedCM As CurrencyManager = sender
           
           ' If so, check to see if the current position is 
           ' not equal to the cached position and the cached 
           ' position is not out of bounds.
           If relatedCM.Position <> cachedPosition AndAlso _
               cachedPosition > 0 AndAlso cachedPosition < _
               relatedCM.Count Then
               relatedCM.Position = cachedPosition
               cachedPosition = -1
           End If
       End If
   End Sub
   

例

次の例では、子テーブルの CurrencyManager.の現在位置を保存し、親テーブルの編集が完了した後に位置をリセットする方法を示します。 この例には、BindingSource コンポーネントを使用して、DataSet 内の 2 つのテーブルにバインドされた 2 つの DataGridView コントロールが含まれています。 2 つのテーブルの間にリレーションシップが確立され、リレーションシップが DataSetに追加されます。 子テーブル内の位置は、デモンストレーションのために最初は 3 行目に設定されます。

using System;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace BT2
{
    public class Form1 : Form
    {
        public Form1()
        {
            InitializeControlsAndDataSource();
        }

        // Declare the controls to be used.
        private BindingSource bindingSource1;
        private DataGridView dataGridView1;
        private Button button1;
        private DataGridView dataGridView2;
        private CheckBox cachePositionCheckBox;
        public DataSet set1;

        private void InitializeControlsAndDataSource()
        {
            // Initialize the controls and set location, size and
            // other basic properties.
            this.dataGridView1 = new DataGridView();
            this.bindingSource1 = new BindingSource();
            this.button1 = new Button();
            this.dataGridView2 = new DataGridView();
            this.cachePositionCheckBox = new System.Windows.Forms.CheckBox();
            this.dataGridView1.ColumnHeadersHeightSizeMode =
                DataGridViewColumnHeadersHeightSizeMode.AutoSize;
            this.dataGridView1.Dock = DockStyle.Top;
            this.dataGridView1.Location = new Point(0, 20);
            this.dataGridView1.Size = new Size(292, 170);
            this.button1.Location = new System.Drawing.Point(18, 175);
            this.button1.Size = new System.Drawing.Size(125, 23);

            button1.Text = "Clear Parent Field";
            this.button1.Click += new System.EventHandler(this.button1_Click);
            this.dataGridView2.ColumnHeadersHeightSizeMode =
                System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
            this.dataGridView2.Location = new System.Drawing.Point(0, 225);
            this.dataGridView2.Size = new System.Drawing.Size(309, 130);
            this.cachePositionCheckBox.AutoSize = true;
            this.cachePositionCheckBox.Checked = true;
            this.cachePositionCheckBox.Location = new System.Drawing.Point(150, 175);
            this.cachePositionCheckBox.Name = "radioButton1";
            this.cachePositionCheckBox.Size = new System.Drawing.Size(151, 17);
            this.cachePositionCheckBox.Text = "Cache and restore position";
            this.ClientSize = new System.Drawing.Size(325, 420);
            this.Controls.Add(this.dataGridView1);
            this.Controls.Add(this.cachePositionCheckBox);
            this.Controls.Add(this.dataGridView2);
            this.Controls.Add(this.button1);

            // Initialize the data.
            set1 = InitializeDataSet();

            // Set the data source to the DataSet.
            bindingSource1.DataSource = set1;

            //Set the DataMember to the Menu table.
            bindingSource1.DataMember = "Customers";

            // Add the control data bindings.
            dataGridView1.DataSource = bindingSource1;

            // Set the data source and member for the second DataGridView.
            dataGridView2.DataSource = bindingSource1;
            dataGridView2.DataMember = "custOrders";

            // Get the currency manager for the customer orders binding.
            CurrencyManager relatedCM =
                bindingSource1.GetRelatedCurrencyManager("custOrders");

            // Set the position in the child table for demonstration purposes.
            relatedCM.Position = 3;

            // Handle the current changed event. This event occurs when
            // the current item is changed, but not when a field of the current
            // item is changed.
            bindingSource1.CurrentChanged +=
                new EventHandler(bindingSource1_CurrentChanged);

            // Handle the two events for caching and resetting the position.
            relatedCM.ListChanged += new ListChangedEventHandler(relatedCM_ListChanged);
            relatedCM.PositionChanged
                += new EventHandler(relatedCM_PositionChanged);

            // Set cacheing to true in case current changed event
            // occurred on set up.
            cacheChildPosition = true;
        }

        // Establish the data set with two tables and a relationship
        // between them.
        private DataSet InitializeDataSet()
        {
            set1 = new DataSet();
            // Declare the DataSet and add a table and column.
            set1.Tables.Add("Customers");
            set1.Tables[0].Columns.Add("CustomerID");
            set1.Tables[0].Columns.Add("Customer Name");
            set1.Tables[0].Columns.Add("Contact Name");

            // Add some rows to the table.
            set1.Tables["Customers"].Rows.Add("c1", "Fabrikam, Inc.", "Ellen Adams");
            set1.Tables[0].Rows.Add("c2", "Lucerne Publishing", "Don Hall");
            set1.Tables[0].Rows.Add("c3", "Northwind Traders", "Lori Penor");
            set1.Tables[0].Rows.Add("c4", "Tailspin Toys", "Michael Patten");
            set1.Tables[0].Rows.Add("c5", "Woodgrove Bank", "Jyothi Pai");

            // Declare the DataSet and add a table and column.
            set1.Tables.Add("Orders");
            set1.Tables[1].Columns.Add("CustomerID");
            set1.Tables[1].Columns.Add("OrderNo");
            set1.Tables[1].Columns.Add("OrderDate");

            // Add some rows to the table.
            set1.Tables[1].Rows.Add("c1", "119", "10/04/2006");
            set1.Tables[1].Rows.Add("c1", "149", "10/10/2006");
            set1.Tables[1].Rows.Add("c1", "159", "10/12/2006");
            set1.Tables[1].Rows.Add("c2", "169", "10/10/2006");
            set1.Tables[1].Rows.Add("c2", "179", "10/10/2006");
            set1.Tables[1].Rows.Add("c2", "189", "10/12/2006");
            set1.Tables[1].Rows.Add("c3", "122", "10/04/2006");
            set1.Tables[1].Rows.Add("c4", "130", "10/10/2006");
            set1.Tables[1].Rows.Add("c5", "1.29", "10/14/2006");

            DataRelation dr = new DataRelation("custOrders",
                set1.Tables["Customers"].Columns["CustomerID"],
                set1.Tables["Orders"].Columns["CustomerID"]);
            set1.Relations.Add(dr);
            return set1;
        }
        private int cachedPosition = -1;
        private bool cacheChildPosition = true;

        void relatedCM_ListChanged(object sender, ListChangedEventArgs e)
        {
            // Check to see if this is a caching situation.
            if (cacheChildPosition && cachePositionCheckBox.Checked)
            {
                // If so, check to see if it is a reset situation, and the current
                // position is greater than zero.
                CurrencyManager relatedCM = sender as CurrencyManager;
                if (e.ListChangedType == ListChangedType.Reset && relatedCM.Position > 0)

                    // If so, cache the position of the child table.
                    cachedPosition = relatedCM.Position;
            }
        }
        void bindingSource1_CurrentChanged(object sender, EventArgs e)
        {
            // If the CurrentChanged event occurs, this is not a caching
            // situation.
            cacheChildPosition = false;
        }
        void relatedCM_PositionChanged(object sender, EventArgs e)
        {
            // Check to see if this is a caching situation.
            if (cacheChildPosition && cachePositionCheckBox.Checked)
            {
                CurrencyManager relatedCM = sender as CurrencyManager;

                // If so, check to see if the current position is
                // not equal to the cached position and the cached
                // position is not out of bounds.
                if (relatedCM.Position != cachedPosition && cachedPosition
                    > 0 && cachedPosition < relatedCM.Count)
                {
                    relatedCM.Position = cachedPosition;
                    cachedPosition = -1;
                }
            }
        }
        int count = 0;
        private void button1_Click(object sender, EventArgs e)
        {
            // For demo purposes--modifies a value in the first row of the
            // parent table.
            DataRow row1 = set1.Tables[0].Rows[0];
            row1[1] = DBNull.Value;
        }

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

Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms



Public Class Form1
    Inherits Form
    
    Public Sub New() 
        InitializeControlsAndDataSource()
    
    End Sub
    
    ' Declare the controls to be used.
    Private WithEvents bindingSource1 As BindingSource
    Private dataGridView1 As DataGridView
    Private WithEvents button1 As Button
    Private dataGridView2 As DataGridView
    Private cachePositionCheckBox As CheckBox
    Public set1 As DataSet
    
    
    Private Sub InitializeControlsAndDataSource() 
        ' Initialize the controls and set location, size and 
        ' other basic properties.
        Me.dataGridView1 = New DataGridView()
        Me.bindingSource1 = New BindingSource()
        Me.button1 = New Button()
        Me.dataGridView2 = New DataGridView()
        Me.cachePositionCheckBox = New System.Windows.Forms.CheckBox()
        Me.dataGridView1.ColumnHeadersHeightSizeMode = _
            DataGridViewColumnHeadersHeightSizeMode.AutoSize
        Me.dataGridView1.Dock = DockStyle.Top
        Me.dataGridView1.Location = New Point(0, 20)
        Me.dataGridView1.Size = New Size(292, 170)
        Me.button1.Location = New System.Drawing.Point(18, 175)
        Me.button1.Size = New System.Drawing.Size(125, 23)
        
        button1.Text = "Clear Parent Field"

        Me.dataGridView2.ColumnHeadersHeightSizeMode = _
            System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize
        Me.dataGridView2.Location = New System.Drawing.Point(0, 225)
        Me.dataGridView2.Size = New System.Drawing.Size(309, 130)
        Me.cachePositionCheckBox.AutoSize = True
        Me.cachePositionCheckBox.Checked = True
        Me.cachePositionCheckBox.Location = New System.Drawing.Point(150, 175)
        Me.cachePositionCheckBox.Name = "radioButton1"
        Me.cachePositionCheckBox.Size = New System.Drawing.Size(151, 17)
        Me.cachePositionCheckBox.Text = "Cache and restore position"
        Me.ClientSize = New System.Drawing.Size(325, 420)
        Me.Controls.Add(Me.dataGridView1)
        Me.Controls.Add(Me.cachePositionCheckBox)
        Me.Controls.Add(Me.dataGridView2)
        Me.Controls.Add(Me.button1)
        
        ' Initialize the data.
        set1 = InitializeDataSet()
        
        ' Set the data source to the DataSet.
        bindingSource1.DataSource = set1
        
        'Set the DataMember to the Menu table.
        bindingSource1.DataMember = "Customers"
        
        ' Add the control data bindings.
        dataGridView1.DataSource = bindingSource1
        
        ' Set the data source and member for the second DataGridView.
        dataGridView2.DataSource = bindingSource1
        dataGridView2.DataMember = "custOrders"
        
        ' Get the currency manager for the customer orders binding.
        Dim relatedCM As CurrencyManager = _
            bindingSource1.GetRelatedCurrencyManager("custOrders")

        ' Handle the two events for caching and resetting the position.
        AddHandler relatedCM.ListChanged, AddressOf relatedCM_ListChanged
        AddHandler relatedCM.PositionChanged, AddressOf relatedCM_PositionChanged
        
        ' Set the position in the child table for demonstration purposes.
        relatedCM.Position = 3

        ' Set cacheing to true in case current changed event
        ' occurred on set up.
        cacheChildPosition = True
      
    
    End Sub
    
    
    
    ' Establish the data set with two tables and a relationship
    ' between them.
    Private Function InitializeDataSet() As DataSet 
        set1 = New DataSet()
        ' Declare the DataSet and add a table and column.
        set1.Tables.Add("Customers")
        set1.Tables(0).Columns.Add("CustomerID")
        set1.Tables(0).Columns.Add("Customer Name")
        set1.Tables(0).Columns.Add("Contact Name")
        
        ' Add some rows to the table.
        set1.Tables("Customers").Rows.Add("c1", "Fabrikam, Inc.", _
            "Ellen Adams")
        set1.Tables(0).Rows.Add("c2", "Lucerne Publishing", "Don Hall")
        set1.Tables(0).Rows.Add("c3", "Northwind Traders", "Lori Penor")
        set1.Tables(0).Rows.Add("c4", "Tailspin Toys", "Michael Patten")
        set1.Tables(0).Rows.Add("c5", "Woodgrove Bank", "Jyothi Pai")
        
        ' Declare the DataSet and add a table and column.
        set1.Tables.Add("Orders")
        set1.Tables(1).Columns.Add("CustomerID")
        set1.Tables(1).Columns.Add("OrderNo")
        set1.Tables(1).Columns.Add("OrderDate")
        
        ' Add some rows to the table.
        set1.Tables(1).Rows.Add("c1", "119", "10/04/2006")
        set1.Tables(1).Rows.Add("c1", "149", "10/10/2006")
        set1.Tables(1).Rows.Add("c1", "159", "10/12/2006")
        set1.Tables(1).Rows.Add("c2", "169", "10/10/2006")
        set1.Tables(1).Rows.Add("c2", "179", "10/10/2006")
        set1.Tables(1).Rows.Add("c2", "189", "10/12/2006")
        set1.Tables(1).Rows.Add("c3", "122", "10/04/2006")
        set1.Tables(1).Rows.Add("c4", "130", "10/10/2006")
        set1.Tables(1).Rows.Add("c5", "1.29", "10/14/2006")
        
        Dim dr As New DataRelation("custOrders", _
            set1.Tables("Customers").Columns("CustomerID"), _
            set1.Tables("Orders").Columns("CustomerID"))
        set1.Relations.Add(dr)
        Return set1
    
    End Function '
    Private cachedPosition As Integer = - 1
    Private cacheChildPosition As Boolean = True
    
    Private Sub relatedCM_ListChanged(ByVal sender As Object, _
        ByVal e As ListChangedEventArgs)
        ' Check to see if this is a caching situation.
        If cacheChildPosition AndAlso cachePositionCheckBox.Checked Then
            ' If so, check to see if it is a reset situation, and the current
            ' position is greater than zero.
            Dim relatedCM As CurrencyManager = sender
            If e.ListChangedType = ListChangedType.Reset _
                AndAlso relatedCM.Position > 0 Then

                ' If so, cache the position of the child table.
                cachedPosition = relatedCM.Position
            End If
        End If

    End Sub

    ' Handle the current changed event. This event occurs when
    ' the current item is changed, but not when a field of the current
    ' item is changed.
    Private Sub bindingSource1_CurrentChanged(ByVal sender As Object, _
        ByVal e As EventArgs) Handles bindingSource1.CurrentChanged
        ' If the CurrentChanged event occurs, this is not a caching 
        ' situation.
        cacheChildPosition = False

    End Sub

    Private Sub relatedCM_PositionChanged(ByVal sender As Object, ByVal e As EventArgs) 
        ' Check to see if this is a caching situation.
        If cacheChildPosition AndAlso cachePositionCheckBox.Checked Then
            Dim relatedCM As CurrencyManager = sender
            
            ' If so, check to see if the current position is 
            ' not equal to the cached position and the cached 
            ' position is not out of bounds.
            If relatedCM.Position <> cachedPosition AndAlso _
                cachedPosition > 0 AndAlso cachedPosition < _
                relatedCM.Count Then
                relatedCM.Position = cachedPosition
                cachedPosition = -1
            End If
        End If
    End Sub

    Private count As Integer = 0
    
    Private Sub button1_Click(ByVal sender As Object, _
        ByVal e As EventArgs) Handles button1.Click
        ' For demo purposes--modifies a value in the first row of the
        ' parent table.
        Dim row1 As DataRow = set1.Tables(0).Rows(0)
        row1(1) = DBNull.Value
    End Sub
     
    <STAThread()>  _
    Shared Sub Main() 
        Application.EnableVisualStyles()
        Application.SetCompatibleTextRenderingDefault(False)
        Application.Run(New Form1())
    
    End Sub
End Class

コード例をテストするには、次の手順を実行します。

1. 例を実行します。

2. キャッシュとリセット位置 チェック ボックスがオンになっていることを確認します。

3. [親フィールドのクリア] ボタンをクリックすると、親テーブルのフィールドが変更されます。 子テーブルで選択されている行は変更されないことに注意してください。

4. この例を閉じて、もう一度実行します。 リセット動作は親行の最初の変更でのみ発生するため、これを行う必要があります。

5. キャッシュをクリアし、位置 をリセットするチェック ボックス。

6. [親フィールド クリア] ボタン クリックします。 子テーブルで選択されている行が最初の行に変わります。

コードのコンパイル

この例では、次のものが必要です。

• System、System.Data、System.Drawing、System.Windows.Forms、および System.XML アセンブリへの参照。

関連項目

• 方法: 同じデータ ソースにバインドされた複数のコントロールを確実に同期
• BindingSource コンポーネント
• データ バインディングと Windows フォーム