DataSet.GetChanges メソッド ()
前回 DataSet を読み取るか、 AcceptChanges を呼び出した以降にこのデータセットに対して行われたすべての変更が格納されているこのデータセットのコピーを取得します。
Overloads Public Function GetChanges() As DataSet
[C#]
public DataSet GetChanges();
[C++]
public: DataSet* GetChanges();
[JScript]
public function GetChanges() : DataSet;
戻り値
アクションを実行した後、 Merge を使用して元のデータセットにマージするために使用できる、この DataSet の変更のコピー。変更がない場合は null 参照 (Visual Basic では Nothing) 。
解説
前回 DataSet を読み取るか、 AcceptChanges を呼び出した以降にこのデータセットに対して行われたすべての変更が格納されているこのデータセットのコピーを取得します。このコピーは、元の DataSet にマージできるよう特別に設計されています。リレーションシップ制約があるために、Unchanged の親行が含まれる場合があります。これらの rowStates の行が見つからない場合、このメソッドは null 参照 (Visual Basic では Nothing) を返します。
使用例
[Visual Basic, C#, C++] 1 つのテーブル、2 列、および 10 行で単純な DataSet を作成する例を次に示します。2 つの値を変更し、1 行追加します。変更されたデータのサブセットは、 GetChanges メソッドを使用して作成されます。エラーを調整した後、新しい列をサブセットに追加し、スキーマを変更します。 missingSchemaAction を MissingSchemaAction.Add に設定して Merge メソッドを呼び出すと、元の DataSet オブジェクトのスキーマに新しい列が追加されます。
Private Sub DemonstrateMerge()
' Create a DataSet with one table, two columns, and three rows.
Dim ds As New DataSet("myDataSet")
Dim t As New DataTable("Items")
Dim c1 As New DataColumn("id", Type.GetType("System.Int32"), "")
c1.AutoIncrement = True
Dim c2 As New DataColumn("Item", Type.GetType("System.Int32"), "")
' DataColumn array to set primary key.
Dim keyCol(1) As DataColumn
Dim r As DataRow
' Create variable for temporary DataSet.
Dim xSet As DataSet
' Add RowChanged event handler for the table.
AddHandler t.RowChanged, AddressOf Row_Changed
ds.Tables.Add(t)
t.Columns.Add(c1)
t.Columns.Add(c2)
' Set primary key column.
keyCol(0) = c1
t.PrimaryKey = keyCol
' Add ten rows.
Dim i As Integer
For i = 0 To 9
r = t.NewRow()
r("Item") = i
t.Rows.Add(r)
Next i
' Accept changes.
ds.AcceptChanges()
PrintValues(ds, "Original values")
' Change row values.
t.Rows(0)("Item") = 50
t.Rows(1)("Item") = 111
' Add one row.
r = t.NewRow()
r("Item") = 74
t.Rows.Add(r)
' Insert code for error checking. Here we set one row in error.
t.Rows(1).RowError = "over 100"
PrintValues(ds, "Modified and New Values")
' If the table has changes or errors, create a subset DataSet.
If ds.HasChanges(DataRowState.Modified Or DataRowState.Added) _
And ds.HasErrors Then
' Use GetChanges to extract subset.
xSet = ds.GetChanges(DataRowState.Modified Or DataRowState.Added)
PrintValues(xSet, "Subset values")
' Insert code to reconcile errors. In this case, we'll reject changes.
Dim xTable As DataTable
For Each xTable In xSet.Tables
If xTable.HasErrors Then
Dim xRow As DataRow
For Each xRow In xTable.Rows
'Console.WriteLine(xRow["Item"]);
If CInt(xRow("Item", DataRowVersion.Current)) > 100 Then
xRow.RejectChanges()
xRow.ClearErrors()
End If
Next xRow
End If
Next xTable
' Add a column to the xSet.
xSet.Tables("Items").Columns.Add(New DataColumn("newColumn"))
PrintValues(xSet, "Reconciled subset values")
' Merge changes back to first DataSet.
ds.Merge(xSet, False, System.Data.MissingSchemaAction.Add)
End If
PrintValues(ds, "Merged Values")
End Sub
Private Sub Row_Changed(sender As Object, e As DataRowChangeEventArgs)
Console.WriteLine("Row Changed " + e.Action.ToString() _
+ ControlChars.Tab + e.Row.ItemArray(0).ToString())
End Sub
Private Sub PrintValues(ds As DataSet, label As String)
Console.WriteLine(label + ControlChars.Cr)
Dim t As DataTable
For Each t In ds.Tables
Console.WriteLine("TableName: " + t.TableName)
Dim r As DataRow
For Each r In t.Rows
Dim c As DataColumn
For Each c In t.Columns
Console.Write(ControlChars.Tab + " " + r(c).ToString())
Next c
Console.WriteLine()
Next r
Next t
End Sub
[C#]
private void DemonstrateMerge(){
// Create a DataSet with one table, two columns, and three rows.
DataSet ds = new DataSet("myDataSet");
DataTable t = new DataTable("Items");
DataColumn c1 = new DataColumn("id", Type.GetType("System.Int32"),"");
c1.AutoIncrement=true;
DataColumn c2 = new DataColumn("Item", Type.GetType("System.Int32"),"");
// DataColumn array to set primary key.
DataColumn[] keyCol= new DataColumn[1];
DataRow r;
// Create variable for temporary DataSet.
DataSet xSet;
// Add RowChanged event handler for the table.
t.RowChanged+=new DataRowChangeEventHandler(Row_Changed);
ds.Tables.Add(t);
t.Columns.Add(c1);
t.Columns.Add(c2);
// Set primary key column.
keyCol[0]= c1;
t.PrimaryKey=keyCol;
// Add ten rows.
for(int i = 0; i <10;i++){
r=t.NewRow();
r["Item"]= i;
t.Rows.Add(r);
}
// Accept changes.
ds.AcceptChanges();
PrintValues(ds, "Original values");
// Change row values.
t.Rows[0]["Item"]= 50;
t.Rows[1]["Item"]= 111;
// Add one row.
r=t.NewRow();
r["Item"]=74;
t.Rows.Add(r);
// Insert code for error checking. Here we set one row in error.
t.Rows[1].RowError= "over 100";
PrintValues(ds, "Modified and New Values");
// If the table has changes or errors, create a subset DataSet.
if(ds.HasChanges(DataRowState.Modified | DataRowState.Added)& ds.HasErrors){
// Use GetChanges to extract subset.
xSet = ds.GetChanges(DataRowState.Modified|DataRowState.Added);
PrintValues(xSet, "Subset values");
// Insert code to reconcile errors. In this case, we'll reject changes.
foreach(DataTable xTable in xSet.Tables){
if (xTable.HasErrors){
foreach(DataRow xRow in xTable.Rows){
//Console.WriteLine(xRow["Item"]);
if((int)xRow["Item",DataRowVersion.Current ]> 100){
xRow.RejectChanges();
xRow.ClearErrors();
}
}
}
}
// Add a column to the xSet.
xSet.Tables["Items"].Columns.Add(new DataColumn("newColumn"));
PrintValues(xSet, "Reconciled subset values");
// Merge changes back to first DataSet.
ds.Merge(xSet,false,System.Data.MissingSchemaAction.Add);
}
PrintValues(ds, "Merged Values");
}
private void Row_Changed(object sender, DataRowChangeEventArgs e){
Console.WriteLine("Row Changed " + e.Action.ToString() + "\t" + e.Row.ItemArray[0]);
}
private void PrintValues(DataSet ds, string label){
Console.WriteLine(label + "\n");
foreach(DataTable t in ds.Tables){
Console.WriteLine("TableName: " + t.TableName);
foreach(DataRow r in t.Rows){
foreach(DataColumn c in t.Columns){
Console.Write("\t " + r[c] );
}
Console.WriteLine();
}
}
}
[C++]
private:
void DemonstrateMerge(){
// Create a DataSet with one table, two columns, and three rows.
DataSet* ds = new DataSet(S"myDataSet");
DataTable* t = new DataTable(S"Items");
DataColumn* c1 = new DataColumn(S"id", Type::GetType(S"System.Int32"),S"");
c1->AutoIncrement=true;
DataColumn* c2 = new DataColumn(S"Item", Type::GetType(S"System.Int32"),S"");
// DataColumn array to set primary key.
DataColumn* keyCol[]= new DataColumn*[1];
DataRow* r;
// Create variable for temporary DataSet.
DataSet* xSet;
// Add RowChanged event handler for the table.
t->RowChanged+=new DataRowChangeEventHandler(this, &Form1::Row_Changed);
ds->Tables->Add(t);
t->Columns->Add(c1);
t->Columns->Add(c2);
// Set primary key column.
keyCol[0]= c1;
t->PrimaryKey=keyCol;
// Add ten rows.
for(int i = 0; i <10;i++){
r=t->NewRow();
r->Item[S"Item"]= __box(i);
t->Rows->Add(r);
}
// Accept changes.
ds->AcceptChanges();
PrintValues(ds, S"Original values");
// Change row values.
t->Rows->Item[0]->Item[S"Item"]= __box(50);
t->Rows->Item[1]->Item[S"Item"]= __box(111);
// Add one row.
r=t->NewRow();
r->Item[S"Item"]=__box(74);
t->Rows->Add(r);
// Insert code for error checking. Here we set one row in error.
t->Rows->Item[1]->RowError= S"over 100";
PrintValues(ds, S"Modified and New Values");
// If the table has changes or errors, create a subset DataSet.
if(ds->HasChanges(static_cast<DataRowState>(DataRowState::Modified | DataRowState::Added))& ds->HasErrors){
// Use GetChanges to extract subset.
xSet = ds->GetChanges(static_cast<DataRowState>(DataRowState::Modified|DataRowState::Added));
PrintValues(xSet, S"Subset values");
// Insert code to reconcile errors. In this case, we'll reject changes.
System::Collections::IEnumerator* myEnum = xSet->Tables->GetEnumerator();
while (myEnum->MoveNext())
{
DataTable* xTable = __try_cast<DataTable*>(myEnum->Current);
if (xTable->HasErrors){
System::Collections::IEnumerator* myEnum1 = xTable->Rows->GetEnumerator();
while (myEnum1->MoveNext())
{
DataRow* xRow = __try_cast<DataRow*>(myEnum1->Current);
//Console.WriteLine(xRow["Item"]);
if(*dynamic_cast<Int32*>(xRow->get_Item(S"Item",DataRowVersion::Current)) > 100){
xRow->RejectChanges();
xRow->ClearErrors();
}
}
}
}
// Add a column to the xSet.
xSet->Tables->Item[S"Items"]->Columns->Add(new DataColumn(S"newColumn"));
PrintValues(xSet, S"Reconciled subset values");
// Merge changes back to first DataSet.
ds->Merge(xSet,false,System::Data::MissingSchemaAction::Add);
}
PrintValues(ds, S"Merged Values");
}
void Row_Changed(Object* /*sender*/, DataRowChangeEventArgs* e){
Console::WriteLine(S"Row Changed {0}\t{1}", __box(e->Action), e->Row->ItemArray[0]);
}
void PrintValues(DataSet* ds, String* label){
Console::WriteLine(S"{0}\n", label);
System::Collections::IEnumerator* myEnum2 = ds->Tables->GetEnumerator();
while (myEnum2->MoveNext())
{
DataTable* t = __try_cast<DataTable*>(myEnum2->Current);
Console::WriteLine(S"TableName: {0}", t->TableName);
System::Collections::IEnumerator* myEnum3 = t->Rows->GetEnumerator();
while (myEnum3->MoveNext())
{
DataRow* r = __try_cast<DataRow*>(myEnum3->Current);
System::Collections::IEnumerator* myEnum4 = t->Columns->GetEnumerator();
while (myEnum4->MoveNext())
{
DataColumn* c = __try_cast<DataColumn*>(myEnum4->Current);
Console::Write(S"\t {0}", r->Item[c] );
}
Console::WriteLine();
}
}
}
[JScript] JScript のサンプルはありません。Visual Basic、C#、および C++ のサンプルを表示するには、このページの左上隅にある言語のフィルタ ボタン .gif)
をクリックします。
必要条件
プラットフォーム: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 ファミリ
参照
DataSet クラス | DataSet メンバ | System.Data 名前空間 | DataSet.GetChanges オーバーロードの一覧 | HasChanges