DataSet.GetChanges Method ()
Gets a copy of the DataSet that contains all changes made to it since it was loaded or since AcceptChanges was last called.
Assembly: System.Data (in System.Data.dll)
Creates a new DataSet that contains a copy of all rows in the original DataSet that have pending changes. Relationship constraints can cause additional unchanged rows to be added to the new DataSet if the unchanged rows contain primary keys corresponding to foreign keys in the changed rows. The method returns null if there are no rows in the original DataSet that have pending changes.
The following example creates a simple DataSet with one table, two columns, and ten rows. Two values are changed, and one row is added. A subset of the changed data is created using the GetChanges method. After reconciling errors, a new column is added to the subset, changing the schema. When the Merge method is called with the missingSchemaAction set to MissingSchemaAction.Add, the new column is added to the original DataSet object's schema.
Private Sub DemonstrateMerge() ' Create a DataSet with one table, two columns, ' and three rows. Dim dataSet As New DataSet("dataSet") Dim table As New DataTable("Items") Dim idColumn As New DataColumn("id", _ Type.GetType("System.Int32"), "") idColumn.AutoIncrement = True Dim itemColumn As New DataColumn("Item", _ Type.GetType("System.Int32"), "") ' Create DataColumn array to set primary key. Dim keyColumn(1) As DataColumn Dim row As DataRow ' Create variable for temporary DataSet. Dim changesDataSet As DataSet ' Add RowChanged event handler for the table. AddHandler table.RowChanged, AddressOf Row_Changed dataSet.Tables.Add(table) table.Columns.Add(idColumn) table.Columns.Add(itemColumn) ' Set primary key column. keyColumn(0) = idColumn table.PrimaryKey = keyColumn ' Add ten rows. Dim i As Integer For i = 0 To 9 row = table.NewRow() row("Item") = i table.Rows.Add(row) Next i ' Accept changes. dataSet.AcceptChanges() PrintValues(dataSet, "Original values") ' Change row values. table.Rows(0)("Item") = 50 table.Rows(1)("Item") = 111 ' Add one row. row = table.NewRow() row("Item") = 74 table.Rows.Add(row) ' Insert code for error checking. Set one row in error. table.Rows(1).RowError = "over 100" PrintValues(dataSet, "Modified and New Values") ' If the table has changes or errors, create a subset DataSet. If dataSet.HasChanges(DataRowState.Modified Or DataRowState.Added) _ And dataSet.HasErrors Then ' Use GetChanges to extract subset. changesDataSet = dataSet.GetChanges( _ DataRowState.Modified Or DataRowState.Added) PrintValues(changesDataSet, "Subset values") ' Insert code to reconcile errors. In this case, reject changes. Dim changesTable As DataTable For Each changesTable In changesDataSet.Tables If changesTable.HasErrors Then Dim changesRow As DataRow For Each changesRow In changesTable.Rows 'Console.WriteLine(changesRow["Item"]); If CInt(changesRow("Item", _ DataRowVersion.Current)) > 100 Then changesRow.RejectChanges() changesRow.ClearErrors() End If Next changesRow End If Next changesTable ' Add a column to the changesDataSet. changesDataSet.Tables("Items").Columns.Add( _ New DataColumn("newColumn")) PrintValues(changesDataSet, "Reconciled subset values") ' Merge changes back to first DataSet. dataSet.Merge(changesDataSet, False, _ System.Data.MissingSchemaAction.Add) End If PrintValues(dataSet, "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(dataSet As DataSet, label As String) Console.WriteLine(label + ControlChars.Cr) Dim table As DataTable For Each table In dataSet.Tables Console.WriteLine("TableName: " + table.TableName) Dim row As DataRow For Each row In table.Rows Dim column As DataColumn For Each column In table.Columns Console.Write(ControlChars.Tab & " " _ & row(column).ToString()) Next column Console.WriteLine() Next row Next table End Sub
Available since 1.1