DataSet.GetChanges DataSet.GetChanges DataSet.GetChanges DataSet.GetChanges Method

定义

获取 DataSet 的副本,该副本包含自上次加载以来或自调用 AcceptChanges() 以来的所有更改。Gets a copy of the DataSet containing all changes made to it since it was last loaded, or since AcceptChanges() was called.

重载

GetChanges() GetChanges() GetChanges() GetChanges()

获取 DataSet 的副本,该副本包含自加载以来或自上次调用 AcceptChanges() 以来对该数据集进行的所有更改。Gets a copy of the DataSet that contains all changes made to it since it was loaded or since AcceptChanges() was last called.

GetChanges(DataRowState) GetChanges(DataRowState) GetChanges(DataRowState) GetChanges(DataRowState)

获取由 DataRowState 筛选的 DataSet 的副本,该副本包含上次加载以来或调用 AcceptChanges() 以来进行的所有更改。Gets a copy of the DataSet containing all changes made to it since it was last loaded, or since AcceptChanges() was called, filtered by DataRowState.

GetChanges() GetChanges() GetChanges() GetChanges()

获取 DataSet 的副本,该副本包含自加载以来或自上次调用 AcceptChanges() 以来对该数据集进行的所有更改。Gets a copy of the DataSet that contains all changes made to it since it was loaded or since AcceptChanges() was last called.

public:
 System::Data::DataSet ^ GetChanges();
public System.Data.DataSet GetChanges ();
member this.GetChanges : unit -> System.Data.DataSet
Public Function GetChanges () As DataSet

返回

DataSet 中更改的副本,可以对该副本执行操作,然后可以使用 Merge(DataSet) 将其合并回去。A copy of the changes from this DataSet that can have actions performed on it and later be merged back in using Merge(DataSet). 如果未找到更改的行,则该方法将返回 nullIf no changed rows are found, the method returns null.

示例

下面的示例创建一个具有DataSet一个表、两列和10行的简单。The following example creates a simple DataSet with one table, two columns, and ten rows. 更改了两个值,并添加了一行。Two values are changed, and one row is added. 使用GetChanges方法创建更改的数据的子集。A subset of the changed data is created using the GetChanges method. 在协调错误后,会将一个新列添加到子集,从而更改架构。After reconciling errors, a new column is added to the subset, changing the schema. 在将设置DataSetMissingSchemaAction.Add的情况下调用Merge missingSchemaAction方法时,会将新列添加到原始对象的架构。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 void DemonstrateMerge()
   {
       // Create a DataSet with one table, two columns, 
       // and three rows.
       DataSet dataSet = new DataSet("dataSet");
       DataTable table = new DataTable("Items");
       DataColumn idColumn = new DataColumn("id", 
           Type.GetType("System.Int32"),"");
       idColumn.AutoIncrement=true;
       DataColumn itemColumn = new DataColumn("Item", 
           Type.GetType("System.Int32"),"");

       // DataColumn array to set primary key.
       DataColumn[] keyColumn= new DataColumn[1];
       DataRow row;

       // Create variable for temporary DataSet. 
       DataSet changesDataSet;

       // Add RowChanged event handler for the table.
       table.RowChanged+=new DataRowChangeEventHandler(
           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.
       for(int i = 0; i <10;i++)
       {
           row=table.NewRow();
           row["Item"]= i;
           table.Rows.Add(row);
       }
       // 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 | 
           DataRowState.Added)&& dataSet.HasErrors)
       {
           // Use GetChanges to extract subset.
           changesDataSet = dataSet.GetChanges(
               DataRowState.Modified|DataRowState.Added);
           PrintValues(changesDataSet, "Subset values");

           // Insert code to reconcile errors. In this case, reject changes.
           foreach(DataTable changesTable in changesDataSet.Tables)
           {
               if (changesTable.HasErrors)
               {
                   foreach(DataRow changesRow in changesTable.Rows)
                   {
                       //Console.WriteLine(changesRow["Item"]);
                       if((int)changesRow["Item",DataRowVersion.Current ]> 100)
                       {
                           changesRow.RejectChanges();
                           changesRow.ClearErrors();
                       }
                   }
               }
           }
           // 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);
       }
       PrintValues(dataSet, "Merged Values");
   }

   private void Row_Changed(object sender, DataRowChangeEventArgs e)
   {
       Console.WriteLine("Row Changed " + e.Action.ToString() 
           + "\table" + e.Row.ItemArray[0]);
   }

   private void PrintValues(DataSet dataSet, string label)
   {
       Console.WriteLine(label + "\n");
       foreach(DataTable table in dataSet.Tables)
       {
           Console.WriteLine("TableName: " + table.TableName);
           foreach(DataRow row in table.Rows)
           {
               foreach(DataColumn column in table.Columns)
               {
                   Console.Write("\table " + row[column] );
               }
               Console.WriteLine();
           }
       }
   }
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(0) 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

注解

创建一个新DataSet的,它包含原始DataSet中具有挂起的更改的所有行的副本。Creates a new DataSet that contains a copy of all rows in the original DataSet that have pending changes. 如果未更改的行包含与更改的行中的外DataSet键相对应的主键,则关系约束可能导致将其他未更改的行添加到新的中。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. 如果原始null DataSet中没有行具有挂起的更改,则该方法将返回。The method returns null if there are no rows in the original DataSet that have pending changes.

另请参阅

GetChanges(DataRowState) GetChanges(DataRowState) GetChanges(DataRowState) GetChanges(DataRowState)

获取由 DataRowState 筛选的 DataSet 的副本,该副本包含上次加载以来或调用 AcceptChanges() 以来进行的所有更改。Gets a copy of the DataSet containing all changes made to it since it was last loaded, or since AcceptChanges() was called, filtered by DataRowState.

public:
 System::Data::DataSet ^ GetChanges(System::Data::DataRowState rowStates);
public System.Data.DataSet GetChanges (System.Data.DataRowState rowStates);
member this.GetChanges : System.Data.DataRowState -> System.Data.DataSet
Public Function GetChanges (rowStates As DataRowState) As DataSet

参数

rowStates
DataRowState DataRowState DataRowState DataRowState

DataRowState 值之一。One of the DataRowState values.

返回

DataSet 的筛选副本,可以对该副本执行操作,然后使用 Merge(DataSet) 将其合并回数据集。A filtered copy of the DataSet that can have actions performed on it, and subsequently be merged back in using Merge(DataSet). 如果未找到所需 DataRowState 的行,则该方法返回 nullIf no rows of the desired DataRowState are found, the method returns null.

示例

下面的示例使用GetChanges方法来创建第二个DataSet对象,然后使用该对象更新数据源。The following example uses the GetChanges method to create a second DataSet object, which is then used to update a data source.

private void UpdateDataSet(DataSet dataSet)
{
    // Check for changes with the HasChanges method first.
    if(!dataSet.HasChanges(DataRowState.Modified)) return;

    // Create temporary DataSet variable and
    // GetChanges for modified rows only.
    DataSet tempDataSet = 
        dataSet.GetChanges(DataRowState.Modified);

    // Check the DataSet for errors.
    if(tempDataSet.HasErrors)
    {
        // Insert code to resolve errors.
    }
    // After fixing errors, update the data source with  
    // the DataAdapter used to create the DataSet.
    adapter.Update(tempDataSet);
}
Private Sub UpdateDataSet(ByVal dataSet As DataSet)
   ' Check for changes with the HasChanges method first.
   If Not dataSet.HasChanges(DataRowState.Modified) Then 
       Exit Sub
   End If

   ' Create temporary DataSet variable and
   ' GetChanges for modified rows only.
   Dim tempDataSet As DataSet = _
       dataSet.GetChanges(DataRowState.Modified)

   ' Check the DataSet for errors.
   If tempDataSet.HasErrors Then
      ' Insert code to resolve errors.
   End If

   ' After fixing errors, update the data source with   
   ' the DataAdapter used to create the DataSet.
   adapter.Update(tempDataSet)
End Sub

注解

方法用于生成第二个DataSet对象,该对象仅包含在原始中引入的更改。 GetChangesThe GetChanges method is used to produce a second DataSet object that contains only the changes introduced into the original. rowStates使用参数可指定新对象应包含的更改类型。Use the rowStates argument to specify the type of changes the new object should include.

此返回的副本旨在合并回原始DataSetThis returned copy is designed to be merged back in to this original DataSet. 关系约束可能会导致包含标记Unchanged为的父行。Relationship constraints may cause parent rows marked Unchanged to be included. 如果未找到所需DataRowState的行,则该方法将null GetChanges返回。If no rows of the desired DataRowState are found, the GetChanges method returns null.

另请参阅

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