ADO.NET中的多數據表操作淺析—修改
作者：鄭佐??????? 2004-8-5
三、更新數據集
首先需要說明的是我這裡去掉了Order Details表，對兩個表的操作只是其中的幾個字段。下面是窗體界面：
圖3-1
單選框用來選擇不同的更新方法。
在DataAccess類中增加兩個類成員變量：
???? private SqlDataAdapter _customerDataAdapter; //客戶數據適配器
???? private SqlDataAdapter _orderDataAdapter; //訂單數據適配器
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customerDataAdapter在構造函數中的初始化為
//實例化_customerDataAdapter
SqlCommand selectCustomerComm = new SqlCommand("GetCustomer",_conn);
selectCustomerComm.CommandType = CommandType.StoredProcedure;
selectCustomerComm.Parameters.Add("@CustomerID",SqlDbType.NChar,5,"CustomerID");
????????
SqlCommand insertCustomerComm = new SqlCommand("AddCustomer",_conn);
insertCustomerComm.CommandType = CommandType.StoredProcedure;
insertCustomerComm.Parameters.Add("@CustomerID",SqlDbType.NChar,5,"CustomerID");
insertCustomerComm.Parameters.Add("@CompanyName",SqlDbType.NVarChar,40,"CompanyName");
insertCustomerComm.Parameters.Add("@ContactName",SqlDbType.NVarChar,30,"ContactName");
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SqlCommand updateCustomerComm = new SqlCommand("UpdateCustomer",_conn);
updateCustomerComm.CommandType = CommandType.StoredProcedure;
updateCustomerComm.Parameters.Add("@CustomerID",SqlDbType.NChar,5,"CustomerID");
updateCustomerComm.Parameters.Add("@CompanyName",SqlDbType.NVarChar,40,"CompanyName");
updateCustomerComm.Parameters.Add("@ContactName",SqlDbType.NVarChar,30,"ContactName");
?????????????
SqlCommand deleteCustomerComm = new SqlCommand("DeleteCustomer",_conn);
deleteCustomerComm.CommandType = CommandType.StoredProcedure;
deleteCustomerComm.Parameters.Add("@CustomerID",SqlDbType.NChar,5,"CustomerID");
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_customerDataAdapter = new SqlDataAdapter(selectCustomerComm);
_customerDataAdapter.InsertCommand = insertCustomerComm;
_customerDataAdapter.UpdateCommand = updateCustomerComm;
_customerDataAdapter.DeleteCommand = deleteCustomerComm;
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上面的代碼完全可以用設計器生成，覺得有些東西自己寫感覺更好，不過代碼還是很多。
對於_orderDataAdapter的初始化同上面的差不多，這裡我們只看訂單增加的處理，下面是存儲過程：
CREATE PROCEDURE? AddOrder
(
???? @OrderID INT OUT,
???? @CustomerID NCHAR(5),
???? @OrderDate DATETIME
)
AS
INSERT INTO Orders
(
???? CustomerID ,
???? OrderDate
)
VALUES
(
???? @CustomerID ,
???? @OrderDate
)
--SELECT @OrderID = @@IDENTITY
SET @OrderID = SCOPE_IDENTITY()
GO
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OrderID自動增長值的獲取通過輸出參數來完成，這個相當不錯，如果使用SqlDataAdapter.RowUpdated事件來處理那效率會很低。
對insertOrderComm對象的定義為：
SqlCommand insertOrderComm = new SqlCommand("AddOrder",_conn);
insertOrderComm.CommandType = CommandType.StoredProcedure;
insertOrderComm.Parameters.Add("@OrderID",SqlDbType.Int,4,"OrderID");
insertOrderComm.Parameters["@OrderID"].Direction = ParameterDirection.Output;
insertOrderComm.Parameters.Add("@OrderDate",SqlDbType.DateTime,8,"OrderDate");
insertOrderComm.Parameters.Add("@CustomerID",SqlDbType.NChar,5,"CustomerID");
?
在實現數據的更新方法之前我們先來明確一些更新邏輯：
對於標記為刪除的行，先刪除訂單表的數據，再刪除客戶表的數據；
對於標記為添加的行，先添加客戶表的數據，再添加訂單表的數據。
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（1）實現用獲取修改過的DataSet的副本子集來更新數據的方法。
這也是調用Xml Web Service更新數據的常用方法，先來看第一個版本，子集的獲取通過DataSet.GetChangs方法來完成。
//使用數據集子集更新數據
public void UpdateCustomerOrders(DatasetOrders ds)
{????????????
???? DataSet dsModified = ds.GetChanges(DataRowState.Modified);//獲取修改過的行
???? DataSet dsDeleted = ds.GetChanges(DataRowState.Deleted);//獲取標記為刪除的行
???? DataSet dsAdded = ds.GetChanges(DataRowState.Added);//獲取增加的行
???? try
???? {???
???????? _conn.Open();//先添加客戶表數據，再添加訂單表數據
???????? if(dsAdded != null)
???????? {
????????????? _customerDataAdapter.Update(dsAdded,"Customers");
????????????? _orderDataAdapter.Update(dsAdded,"Orders");
????????????? ds.Merge(dsAdded);
???????? }
???????? if(dsModified != null)//更新數據表
???????? {
???????? ???? _customerDataAdapter.Update(dsModified,"Customers");
????????????? _orderDataAdapter.Update(dsModified,"Orders");
????????????? ds.Merge(dsModified);
???????? }
???????? if(dsDeleted != null)//先刪除訂單表數據，再刪除客戶表數據
???????? {
????????????? _orderDataAdapter.Update(dsDeleted,"Orders");
????????????? _customerDataAdapter.Update(dsDeleted,"Customers");
????????????? ds.Merge(dsDeleted);
???????? }?????????????????
???? }
???? catch(Exception ex)
???? {
???????? throw new Exception("更新數據出錯",ex);
???? }
???? finally
???? {
???????? if(_conn.State != ConnectionState.Closed)
????????????? _conn.Close();
???? }
}
上面的方法看上去比較清晰，不過效率不會很高，至少中間創建了三個DataSet，然後又進行了多次合併。
（2）另一方法就是引用更新，不創建副本。
相對來說性能會高許多，但是如果用在Web服務上傳輸的數據量會更大(可以結合兩個方法進行改進)。具體的實現就是通過DataTable.Select方法選擇行狀態來實現。
//引用方式更新數據
public void UpdateCustomerOrders(DataSet ds)
{
???? try
???? {???
???????? _conn.Open();
???????? //先添加客戶表數據，再添加訂單表數據 ???? _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.Added));
???? _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.Added));
???? //更新數據表
???? _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.ModifiedCurrent));
???? _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.ModifiedCurrent));
//先刪除訂單表數據，再刪除客戶表數據
???? _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.Deleted));
???? _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.Deleted));???????????
???? }
???? catch(Exception ex)
???? {
???????? throw new Exception("更新數據出錯",ex);
???? }
???? finally
???? {
???????? if(_conn.State != ConnectionState.Closed)
????????????? _conn.Close();
???? }
}
結合上面的兩個方法我們可想到調用Web Service有更合理的方法來完成。
（3）使用事務
public void UpdateCustomerOrdersWithTransaction(DataSet ds)
{
???? SqlTransaction trans = null;
???? try
???? {???
???????? _conn.Open();
???????? trans = _conn.BeginTransaction();
???????? _customerDataAdapter.DeleteCommand.Transaction = trans;
???????? _customerDataAdapter.InsertCommand.Transaction = trans;
???????? _customerDataAdapter.UpdateCommand.Transaction = trans;
???????? _orderDataAdapter.DeleteCommand.Transaction = trans;
???????? _orderDataAdapter.InsertCommand.Transaction = trans;
???????? _orderDataAdapter.UpdateCommand.Transaction = trans;
???? _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.Added));
?????????????????? _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.Added));
???? _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.ModifiedCurrent));
???? _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.ModifiedCurrent));
???? _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.Deleted));
???? _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.Deleted));?
???? ???? trans.Commit();
???? }
???? catch(Exception ex)
???? {
???????? trans.Rollback();
???????? throw new Exception("更新數據出錯",ex);
???? }
???? finally
???? {
???????? if(_conn.State != ConnectionState.Closed)
????????????? _conn.Close();
???? }
}
最後讓我們來看看窗體的按鈕更新事件的代碼：
private void buttonUpdate_Click(object sender, System.EventArgs e)
{
????????????? //提交編輯數據
???? this.BindingContext[this._ds].EndCurrentEdit();
????
???? if(radioButtonRef.Checked == true)//引用方式更新
???????? _dataAccess.UpdateCustomerOrders((DataSet)_ds);
???? else if(radioButtonTrans.Checked == true)//啟用事務更新數據表
???????? _dataAccess.UpdateCustomerOrdersWithTransaction((DataSet)_ds);
???? else
???? {
???????? DatasetOrders changedData =? (DatasetOrders)_ds.GetChanges();
???????? if(radioButtonWeb.Checked == true)//Web服務的更正更新
???????? {?????????????????????
????????????? _dataAccess.UpdateCustomerOrders((DataSet)changedData);
???????? }
???????? else//創建副本合併方式更新
???????? {?????????????????
????????????? _dataAccess.UpdateCustomerOrders(changedData);
???????? }
???????? //去除訂單表中添加的虛擬行
???????? foreach(DataRow row in _ds.Orders.Select("","",DataViewRowState.Added))
????????????? _ds.Orders.RemoveOrdersRow((DatasetOrders.OrdersRow)row);
???????? //去除客戶表中添加的虛擬行
???????? foreach(DataRow row in _ds.Customers.Select("","",DataViewRowState.Added))
????????????? _ds.Customers.RemoveCustomersRow((DatasetOrders.CustomersRow)row);
???????? _ds.Merge(changedData);
???? }
???? //提交數據集狀態
???? _ds.AcceptChanges();
}
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本文參考：《ADO.NET Core Reference》
歡迎交流：(秋楓的Blog)http://blog.csdn.net/zhzuo
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