更新數據集
首先需要說明的是我這裏去掉了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
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
customerDataAdapter在構造函數中的初始化爲
//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");
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");
_customerDataAdapter = new SqlDataAdapter(selectCustomerComm);
_customerDataAdapter.InsertCommand = insertCustomerComm;
_customerDataAdapter.UpdateCommand = updateCustomerComm;
_customerDataAdapter.DeleteCommand = deleteCustomerComm;
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，這裏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 //使用觸發器有可能出現問題
SET @OrderID = SCOPE_IDENTITY()
GO
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對象的定義爲：
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：
對於標記爲刪除的行，先刪除訂單表的數據，再刪除客戶表的數據；
對於標記爲添加的行，先添加客戶表的數據，再添加訂單表的數據。
（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);//獲取標記爲刪除的行
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)//啓用事務更新數據表
_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();
}