DataRowView クラスとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

DataRowView クラス

DataRow のカスタマイズされたビューを表します。

名前空間: System.Data
アセンブリ: System.Data (system.data.dll 内)
構文

Visual Basic (宣言)

Public Class DataRowView
    Implements ICustomTypeDescriptor, IEditableObject, IDataErrorInfo,
 INotifyPropertyChanged

Visual Basic (使用法)

Dim instance As DataRowView

public class DataRowView : ICustomTypeDescriptor,
 IEditableObject, IDataErrorInfo, 
    INotifyPropertyChanged

C++

public ref class DataRowView : ICustomTypeDescriptor,
 IEditableObject, IDataErrorInfo, 
    INotifyPropertyChanged

public class DataRowView implements ICustomTypeDescriptor,
 IEditableObject, 
    IDataErrorInfo, INotifyPropertyChanged

JScript

public class DataRowView implements ICustomTypeDescriptor,
 IEditableObject, 
    IDataErrorInfo, INotifyPropertyChanged

解説

データを DataGrid コントロールなどで表示する場合、1 行につき 1 つのバージョンだけを表示できます。表示されている行は DataRowView です。

DataRowView は、Default、Original、Current、および Proposed という 4 種類のバージョン状態のいずれか 1 つになります。

DataRow で BeginEdit を呼び出した後で編集した値は Proposed 値になります。CancelEdit または EndEdit のどちらかを呼び出すまでは、行には Original バージョンと Proposed バージョンが格納されています。CancelEdit を呼び出すと、提示されたバージョンが破棄され、値が Original に戻ります。EndEdit を呼び出すと、DataRowView には Proposed バージョンがなくなり、提示された値が現在の値になります。既定値は、既定値が定義されている列を含む行でだけ使用できます。

使用例

RowVersion プロパティを使用して、DataRowView 内の行の状態を確認する例を次に示します。

Visual Basic

Private Sub DemonstrateRowVersion()
    Dim i As Integer
    ' Create a DataTable with one column.
    Dim table As New DataTable("Table")
    Dim column As New DataColumn("Column")
    table.Columns.Add(column)

    ' Add ten rows.
    Dim row As DataRow
    For i = 0 To 9
        row = table.NewRow()
        row("Column") = "item "
 + i.ToString()
        table.Rows.Add(row)
    Next i
    table.AcceptChanges()

    ' Create a DataView with the table.
    Dim view As New DataView(table)

    ' Change one row's value:
    table.Rows(1)("Column") = "Hello"

    ' Add one row:
    row = table.NewRow()
    row("Column") = "World"
    table.Rows.Add(row)

    ' Set the RowStateFilter to display only added and modified rows.
    view.RowStateFilter = _
       DataViewRowState.Added Or DataViewRowState.ModifiedCurrent

    ' Print those rows. Output includes "Hello" and "World".
    PrintView(view, "ModifiedCurrent and Added")

    ' Set filter to display only originals of modified rows.
    view.RowStateFilter = DataViewRowState.ModifiedOriginal
    PrintView(view, "ModifiedOriginal")

    ' Delete three rows.
    table.Rows(1).Delete()
    table.Rows(2).Delete()
    table.Rows(3).Delete()

    ' Set the RowStateFilter to display only deleted rows.
    view.RowStateFilter = DataViewRowState.Deleted
    PrintView(view, "Deleted")

    ' Set filter to display only current rows.
    view.RowStateFilter = DataViewRowState.CurrentRows
    PrintView(view, "Current")

    ' Set filter to display only unchanged rows.
    view.RowStateFilter = DataViewRowState.Unchanged
    PrintView(view, "Unchanged")

    ' Set filter to display only original rows.
    ' Current values of unmodified rows are also returned.
    view.RowStateFilter = DataViewRowState.OriginalRows
    PrintView(view, "OriginalRows")
End Sub

Private Sub PrintView(ByVal
 view As DataView, ByVal label As
 String)
    Console.WriteLine(ControlChars.Cr + label)
    Dim i As Integer
    For i = 0 To view.Count - 1
        Console.WriteLine(view(i)("Column"))
        Console.WriteLine("DataRowView.RowVersion: {0}",
 _
            view(i).RowVersion)
    Next i
End Sub

private static void DemonstrateRowVersion()
{
    // Create a DataTable with one column.
    DataTable table = new DataTable("Table");
    DataColumn column = new DataColumn("Column");
    table.Columns.Add(column);

    // Add ten rows.
    DataRow row;
    for (int i = 0; i < 10; i++)
    {
        row = table.NewRow();
        row["Column"] = "item " + i;
        table.Rows.Add(row);
    }

    table.AcceptChanges();
    // Create a DataView with the table.
    DataView view = new DataView(table);

    // Change one row's value:
    table.Rows[1]["Column"] = "Hello";

    // Add one row:
    row = table.NewRow();
    row["Column"] = "World";
    table.Rows.Add(row);

    // Set the RowStateFilter to display only added 
    // and modified rows.
    view.RowStateFilter = DataViewRowState.Added | 
        DataViewRowState.ModifiedCurrent;

    // Print those rows. Output includes "Hello" and "World".
    PrintView(view, "ModifiedCurrent and Added");

    // Set filter to display only originals of modified rows.
    view.RowStateFilter = DataViewRowState.ModifiedOriginal;
    PrintView(view, "ModifiedOriginal");

    // Delete three rows.
    table.Rows[1].Delete();
    table.Rows[2].Delete();
    table.Rows[3].Delete();

    // Set the RowStateFilter to display only deleted rows.
    view.RowStateFilter = DataViewRowState.Deleted;
    PrintView(view, "Deleted");

    // Set filter to display only current rows.
    view.RowStateFilter = DataViewRowState.CurrentRows;
    PrintView(view, "Current");

    // Set filter to display only unchanged rows.
    view.RowStateFilter = DataViewRowState.Unchanged;
    PrintView(view, "Unchanged");

    // Set filter to display only original rows.
    // Current values of unmodified rows are also returned.
    view.RowStateFilter = DataViewRowState.OriginalRows;
    PrintView(view, "OriginalRows");
}

private static void PrintView(DataView
 view, string label)
{
    Console.WriteLine("\n" + label);
    for (int i = 0; i < view.Count; i++)
    {
        Console.WriteLine(view[i]["Column"]);
        Console.WriteLine("DataViewRow.RowVersion: {0}", 
            view[i].RowVersion);
    }
}