DataTable.ColumnChanged イベントとは何？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

DataTable.ColumnChanged イベント

DataRow 内の指定した DataColumn の値が変更された後に発生します。

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

Visual Basic (宣言)

Public Event ColumnChanged As
 DataColumnChangeEventHandler

Visual Basic (使用法)

Dim instance As DataTable
Dim handler As DataColumnChangeEventHandler

AddHandler instance.ColumnChanged, handler

public event DataColumnChangeEventHandler ColumnChanged

C++

public:
event DataColumnChangeEventHandler^ ColumnChanged {
    void add (DataColumnChangeEventHandler^ value);
    void remove (DataColumnChangeEventHandler^ value);
}

/** @event */
public void add_ColumnChanged (DataColumnChangeEventHandler
 value)

/** @event */
public void remove_ColumnChanged (DataColumnChangeEventHandler
 value)

JScript

JScript では、イベントは使用できますが、新規に宣言することはできません。

解説

詳細については、「DataTable イベントの使用」を参照してください。

使用例

Visual Basic

Private Shared Sub DataTableColumnChanged()
    Dim custTable As DataTable = New
 DataTable("Customers")
    ' add columns
    custTable.Columns.Add("id", Type.GetType("System.Int32"))
    custTable.Columns.Add("name", Type.GetType("System.String"))
    custTable.Columns.Add("address", Type.GetType("System.String"))

    ' set PrimaryKey
    custTable.Columns("id").Unique = true
    custTable.PrimaryKey = New DataColumn() { custTable.Columns("id")
 }

    ' add a ColumnChanged event handler for the table.
    AddHandler custTable.ColumnChanged, _
        New DataColumnChangeEventHandler(AddressOf
 Column_Changed )


    ' add ten rows
    Dim id As Integer
    For id = 1 To 10
        custTable.Rows.Add( _
            New Object() { id, string.Format("customer{0}",
 id), _
                string.Format("address{0}",
 id) })
    Next
    
    custTable.AcceptChanges()

    ' change the name column in all the rows
    Dim row As DataRow
    For Each row In custTable.Rows
 
        row("name") = string.Format("vip{0}",
 row("id"))
    Next

End Sub

Private Shared Sub Column_Changed(sender
 As Object, _
    e As DataColumnChangeEventArgs)
    Console.WriteLine("Column_Changed Event: name={0}; Column={1};
 original name={2}", _
        e.Row("name"), e.Column.ColumnName, e.Row("name",
 DataRowVersion.Original))
End Sub

private static void DataTableColumnChanged()
{
    DataTable custTable = new DataTable("Customers");
    // add columns
    custTable.Columns.Add("id", typeof(int));
    custTable.Columns.Add("name", typeof(string));
    custTable.Columns.Add("address", typeof(string));

    // set PrimaryKey
    custTable.Columns["id"].Unique = true;
    custTable.PrimaryKey = new DataColumn[] { custTable.Columns["id"]
 };

    // add a ColumnChanged event handler for the table.
    custTable.ColumnChanged += new 
        DataColumnChangeEventHandler(Column_Changed );


    // add ten rows
    for(int id=1; id<=10; id++)
    {
        custTable.Rows.Add(
            new object[] { id, string.Format("customer{0}",
 id), 
            string.Format("address{0}", id) });
    }

    custTable.AcceptChanges();

    // change the name column in all the rows
    foreach(DataRow row in custTable.Rows )
    {
        row["name"] = string.Format("vip{0}",
 row["id"]);
    }

}

private static void Column_Changed(object
 sender, DataColumnChangeEventArgs e )
{
    Console.WriteLine("Column_Changed Event: name={0}; Column={1}; original
 name={2}", 
        e.Row["name"], e.Column.ColumnName, e.Row["name", DataRowVersion.Original]);
}