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示例來自 MSDN，將四個(gè)表關(guān)聯(lián)在一起，適應(yīng)于在操作多表時(shí)，有時(shí)需要關(guān)聯(lián)表有時(shí)不需要關(guān)聯(lián)的情況下（見 CommunityServer 的 cs_shared_Threads_GetThreadSet 存儲(chǔ)過程也屬此類應(yīng)用）。

using System;
using System.Data;
using System.Data.SqlClient;

namespace TestDataRelation
{

    class Program
    {
        static void Main()
        {
            PrintOrders("server=(local); uid=sa; pwd=; database=Test_DataSet_DataRelation");
        }

        private static void PrintOrders(string connectionString)
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                DataSet customerOrders = new DataSet();

                connection.Open();

                SqlDataAdapter reader;

                reader = new SqlDataAdapter("SELECT * FROM Customers", connection);
                reader.Fill(customerOrders, "Customers");

                reader = new SqlDataAdapter("SELECT * FROM Orders", connection);
                reader.Fill(customerOrders, "Orders");

                reader = new SqlDataAdapter("SELECT * FROM OrderDetails", connection);
                reader.Fill(customerOrders, "OrderDetails");

                reader = new SqlDataAdapter("SELECT * FROM Products", connection);
                reader.Fill(customerOrders, "Products");

                connection.Close();

                DataRelation customerOrdersRelation = customerOrders.Relations.Add("CustOrders", customerOrders.Tables["Customers"].Columns["CustomerID"], customerOrders.Tables["Orders"].Columns["CustomerID"]);
                DataRelation orderDetailRelation = customerOrders.Relations.Add("OrderDetail", customerOrders.Tables["Orders"].Columns["OrderID"], customerOrders.Tables["OrderDetails"].Columns["OrderID"], false);
                DataRelation orderProductRelation = customerOrders.Relations.Add("OrderProducts", customerOrders.Tables["Products"].Columns["ProductID"], customerOrders.Tables["OrderDetails"].Columns["ProductID"]);

                // 打印所有訂單及訂單詳情
                foreach (DataRow custRow in customerOrders.Tables["Customers"].Rows)
                {
                    Console.WriteLine("客戶 ID: " + custRow["CustomerID"] + "\t客戶姓名: " + custRow["CustomerName"]);
                    Console.WriteLine("----------------------------------------");

                    foreach (DataRow orderRow in custRow.GetChildRows(customerOrdersRelation))
                    {
                        Console.WriteLine("  訂單號(hào): " + orderRow["OrderID"]);
                        Console.WriteLine("\t訂單日期: " + orderRow["OrderDate"]);

                        foreach (DataRow detailRow in orderRow.GetChildRows(orderDetailRelation))
                        {
                            Console.WriteLine("\t Product: " + detailRow.GetParentRow(orderProductRelation)["ProductName"]);
                            Console.WriteLine("\t Quantity: " + detailRow["Quantity"]);
                        }

                        Console.WriteLine();
                    }
                }

            }
        }
    }

}

MSDN:

請(qǐng)注意，當(dāng)為 Customers 表和 Orders 表創(chuàng)建 DataRelation 時(shí)，沒有為 createConstraints 標(biāo)志指定任何值（默認(rèn)為 true）。它假定 Orders 表中的所有行都具有一個(gè)存在于父 Customers 表中的 CustomerID 值。如果 CustomerID 存在于 Customers 表之外的 Orders 表中，則 ForeignKeyConstraint 將引發(fā)異常。

如果子列可能包含父列不包含的值，添加 DataRelation 時(shí)請(qǐng)將 createConstraints 標(biāo)志設(shè)置為 false。在該示例中，對(duì)于 Orders 表和 OrderDetails 表之間的 DataRelation，createConstraints 標(biāo)志將設(shè)置為 false。這樣，應(yīng)用程序就可以返回 OrderDetails 表中的所有記錄并只返回 Orders 表中記錄的子集，而不會(huì)生成運(yùn)行時(shí)異常。