如何通过 SQL 查询在 dapper 接口（IDBConnection）中使用 automapper答案

【问题标题】：How to use automapper in dapper interface(IDBConnection) with SQL queries如何通过 SQL 查询在 dapper 接口（IDBConnection）中使用 automapper
【发布时间】：2017-02-21 05:48:14
【问题描述】：

public IEnumerable<voucher> index(string word, string DivisionCode, string yearlabel, int pageno)
        {
            using (IDbConnection dbConnection = Connection)
            {
                var data = dbConnection.Query<fydates>(@"SELECT REPLACE(CONVERT(NVARCHAR(10),fystart,6),' ','-') as fystart,
                REPLACE(CONVERT(NVARCHAR(10),fyend,6),' ','-') as fyend FROM fydates WHERE yearlabel = @yearlabel",
                new { yearlabel = yearlabel }).Single();

                List<voucher> DataQuery = dbConnection.Query<voucher, accounts, division, LockStatus, voucher>(@"SELECT V.id,V.voucherno,
                CASE WHEN V.vouchertype='P' THEN 'Paid' ELSE 'Receipt' END AS vouchertype,
                REPLACE(CONVERT(NVARCHAR(10),V.dated,6),' ','-') AS dated,V.subno,V.amount,COALESCE(V.syscreated,' ') AS syscreated,V.bankcode,
                COALESCE(V.cheqno,' ') AS Cheqno,V.Cheqdate,V.posted,V.currency,A.id as accountsid,A.achead,A.shortname,
                D.id as divisionid,D.divname,D.divncode,L.id as lockstatusid,L.name FROM voucher V
                LEFT JOIN Accounts A ON V.bankcode = A.mainac
                LEFT JOIN divisionmst D ON V.divisionid = D.divncode
                LEFT JOIN LockStatus L ON V.posted=L.Type
                WHERE (V.voucherno + V.Subno+V.cheqno + A.achead + LEFT(yearvoucherno,3) LIKE @word AND
                D.divncode LIKE @DivisionCode) AND (dated BETWEEN @fystart AND @fyend OR dated='31-Mar-49')
                Order By V.id DESC OFFSET @pageno *25 ROWS FETCH NEXT 25 ROWS only",
                (voucher, accounts, division, LockStatus) =>
                {
                    voucher.accounts = accounts;
                    voucher.division = division;
                    voucher.LockStatus = LockStatus;
                    return voucher;
                },
                new { word = word, fystart = data.fystart, fyend = data.fyend, DivisionCode = DivisionCode, pageno = pageno - 1 },
                splitOn: "accountsid, divisionid, lockstatusid").ToList();
                return DataQuery;
            }
        }

在较早的场景中，我在 JOINS 查询中使用了 spliton 映射技术，它非常有效。但是在联合查询或条件的情况下，我被卡住了，因为我无法决定我应该在哪里拆分。如上所述，当条件我无法决定在哪里拆分时，联合和案例

【问题讨论】：

标签： c# asp.net-mvc .net-core dapper

【解决方案1】：

只需添加虚拟列即可帮助 Dapper 知道在哪里拆分。请注意，如果虚拟列为空，则关联对象将为空。另请注意，您的目标对象上不需要存在虚拟列。

select
--first object
1 AS Id,
(1+1) AS APropertyAssociatedToYourFirstObject,
(1+1) AS ADifferentPropertyAssociatedToYourFirstObject,

--second object (assuming you are splitting on Id)
1 AS Id,
(1+1) AS APropertyAssociatedToYourSecondObject,
(1+1) AS ADifferentPropertyAssociatedToYourSecondObject
from YourTable

另外，这样排列可以节省大量时间。

【讨论】：