Linq 可查询 - 联接两个没有关系的表

Question

首先，这是针对遗留应用程序，因此我无法从根本上更改任何逻辑。

我有数据库，有两个没有任何关系的表。我问我是否改变这个，但被告知我不能。

这些表可以描述为

Create Table T1
    [doc_id] [int] NOT NULL,                   -- Primary Key
    [customer_acc_no] [varchar](16) NULL,
    [gcompany] [varchar](30) NULL,
    ....
    extra fields 

和表格

Create Table T2
    [UserURN] [int] NOT NULL,                  -- All three fields make up
    [AccountNumber] [varchar](20) NOT NULL,    -- the primary key
    [Company] [varchar](50) NOT NULL,
    ....
    extra fields 

如您所见，不仅字段名称不同，而且它们的长度也不同。

我正在使用存储库和工作单元模式。到目前为止，我已经设法编写了以下内容：

private IRepository<T1> _t1Repository;
private IRepository<T2> _t2Repository;

这些填充在构造函数中。

接下来，我使用以下代码来配置获取可查询的存储库。

var retVal = _t1Repository.Queryable();

由此，我正在尝试添加以下连接。

from q in T1
join w in T2
on new { X1 = q.gcompany, X2 = q.Customer_acc_no } 
equals new { X1 = w.Company, X2 = w.AccountNumber }

我认为它将是这样的：

var query = T1.GroupJoin(T2,
        c => c.gcompany,
        o => o.Company,
        (c, result) => new Result(c.doc_id, result))
    .GroupJoin(T2,
        c => c.Customer_acc_no,
        o => o.AccountNumber ,
        (c, result) => new Result(c.doc_id, result));

但我不确定，因为到目前为止，所有尝试都以Visual Studio中的错误告终。

Answer 1

请参阅下面的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
namespace ConsoleApplication42
{
    class Program
    {
        static void Main(string[] args)
        {
            DataTable dt1 = new DataTable();
            dt1.Columns.Add("doc_id", typeof(int));
            dt1.Columns.Add("customer_acc_no", typeof(string));
            dt1.Columns.Add("gcompany", typeof(string));
            dt1.Rows.Add(new object[] { 1, "100", "abc" });
            dt1.Rows.Add(new object[] { 2, "100", "def" });
            dt1.Rows.Add(new object[] { 3, "100", "def" });
            dt1.Rows.Add(new object[] { 4, "101", "abc" });
            dt1.Rows.Add(new object[] { 5, "101", "ghi" });
            dt1.Rows.Add(new object[] { 6, "102", "jkl" });
            dt1.Rows.Add(new object[] { 7, "102", "abc" });
            dt1.Rows.Add(new object[] { 8, "102", "def" });
            dt1.Rows.Add(new object[] { 9, "103", "abc" });
            dt1.Rows.Add(new object[] { 10, "103", "abc" });

            DataTable dt2 = new DataTable();
            dt2.Columns.Add("UserURN", typeof(int));
            dt2.Columns.Add("AccountNumber", typeof(string));
            dt2.Columns.Add("Company", typeof(string));
            dt2.Rows.Add(new object[] { 11, "100", "abc" });
            dt2.Rows.Add(new object[] { 12, "100", "def" });
            dt2.Rows.Add(new object[] { 13, "100", "def" });
            dt2.Rows.Add(new object[] { 14, "101", "abc" });
            dt2.Rows.Add(new object[] { 15, "101", "ghi" });
            dt2.Rows.Add(new object[] { 16, "102", "jkl" });
            dt2.Rows.Add(new object[] { 17, "102", "abc" });
            dt2.Rows.Add(new object[] { 18, "102", "def" });
            dt2.Rows.Add(new object[] { 19, "103", "abc" });
            dt2.Rows.Add(new object[] { 20, "103", "abc" });
            var results = from r1 in dt1.AsEnumerable()
                          join r2 in dt2.AsEnumerable() on
                             new { x1 = r1.Field<string>("customer_acc_no"), x2 = r1.Field<string>("gcompany") } equals
                             new { x1 = r2.Field<string>("AccountNumber"), x2 = r2.Field<string>("Company") }
                          select new { t1 = r1, t2 = r2 };
        }
    }
}