用多个输出包装多个查询

Question

我有这个 class，我在其中封装了 dapper 调用以执行类似

的操作

var results = SqlWrapper.ExecuteQuery<Product,Customer>("SELECT id FROM Products; SELECT id FROM Customers;");

哪里

results[0] = List<Product>
results[1] = List<Customer>

我支持1,2,3个输出对象，但想随意。 class 也很丑陋，充满了复制和粘贴代码。我考虑是否要通过可选地传递连接来重用连接，但代码似乎不干净。我真正想要的是一种定义 params T[] 的方法，但据我所知，这是行不通的。这个代码可以是 cleaned/shortened 吗？

using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using Dapper;

namespace SqlWrapper
{
    public static class SqlWrapper
    {
        private const string SqlConnectionString = "Server=localhost;Database=TTDS;User Id=sa;Password=sa;";


        public static List<T> ExecuteQuery<T>(string sql, object param = null, SqlConnection sqlConnection = null)
        {
            if (sqlConnection != null)
            {
                return sqlConnection.Query<T>(sql, param).ToList();
            }

            using (var tempSqlConnection = new SqlConnection(SqlConnectionString))
            {
                tempSqlConnection.Open();
                return tempSqlConnection.Query<T>(sql, param).ToList();
            }
        }


        public static List<dynamic> ExecuteQuery<T1, T2>(string sql, object param = null, SqlConnection sqlConnection = null)
        {
            if (sqlConnection != null)
            {
                return MultiQuery<T1, T2>(sqlConnection, sql, param);
            }

            using (var tempSqlConnection = new SqlConnection(SqlConnectionString))
            {
                return MultiQuery<T1, T2>(tempSqlConnection, sql, param);
            }
        }

        public static List<dynamic> ExecuteQuery<T1, T2, T3>(string sql, object param = null,
            SqlConnection sqlConnection = null)
        {
            if (sqlConnection != null)
            {
                return MultiQuery<T1, T2, T3>(sqlConnection, sql, param);
            }

            using (var tempSqlConnection = new SqlConnection(SqlConnectionString))
            {
                return MultiQuery<T1, T2, T3>(tempSqlConnection, sql, param);
            }
        }

        private static List<dynamic> MultiQuery<T1, T2>(SqlConnection sqlConnection, string sql, object param = null)
        {
            var rv = new List<dynamic>();

            using (var grid = sqlConnection.QueryMultiple(sql, param))
            {
                rv.Add(grid.Read<T1>().ToList());
                rv.Add(grid.Read<T2>().ToList());
            }

            return rv;
        }

        private static List<dynamic> MultiQuery<T1, T2, T3>(SqlConnection sqlConnection, string sql, object param = null)
        {
            var rv = new List<dynamic>();

            using (var grid = sqlConnection.QueryMultiple(sql, param))
            {
                rv.Add(grid.Read<T1>().ToList());
                rv.Add(grid.Read<T2>().ToList());
                rv.Add(grid.Read<T3>().ToList());
            }

            return rv;
        }


        public static void ExecuteNonQuery(SqlConnection sqlConnection, string sql, object param, int? timeout = null)
        {
            if (sqlConnection != null)
            {
                sqlConnection.Execute(sql, param, commandTimeout: timeout);
            }
            else
            {
                using (var tempSqlConnection = new SqlConnection(SqlConnectionString))
                {
                    tempSqlConnection.Open();
                    tempSqlConnection.Execute(sql, param, commandTimeout: timeout);
                }
            }
        }
    }
}

Answer 1

这里有一些未经测试的代码，展示了我的一些想法。

虽然 "using" 非常棒，但如果您有选择地先创建连接，然后在必要时将 sqlConnection 置于 finally 块中，则可以减少一些代码。
如果您 return 一个 Tuple<List<T>,List<U>,List<V>> 您可以拥有可以轻松使用的强类型 return 值
如果您从不太复杂的函数中调用最复杂的函数，则可以最大限度地减少重复代码。

public static class SqlWrapper
{
    private const string SqlConnectionString = "Server=localhost;Database=TTDS;User Id=sa;Password=sa;";

    private class NoResult { }

    public static List<T1> ExecuteQuery<T1>(string sql, object param = null, SqlConnection sqlConnection = null)
    {
        return ExecuteQuery<T1, NoResult, NoResult>(sql, param, sqlConnection).Item1;
    }

    public static Tuple<List<T1>, List<T2>> ExecuteQuery<T1, T2>(string sql, object param = null, SqlConnection sqlConnection = null)
    {
        var result = ExecuteQuery<T1, T2, NoResult>(sql, param, sqlConnection);
        return Tuple.Create(result.Item1, result.Item2);
    }

    public static Tuple<List<T1>, List<T2>, List<T3>> ExecuteQuery<T1, T2, T3>(string sql, object param = null, SqlConnection sqlConnection = null)
    {
        List<T1> list1;
        List<T2> list2 = null;
        List<T3> list3 = null;
        bool needsDisposed = false;

        if (sqlConnection == null)
        {
            sqlConnection = new SqlConnection(SqlConnectionString);
            sqlConnection.Open();
            needsDisposed = true;
        }

        try
        {
            using (var grid = sqlConnection.QueryMultiple(sql, param))
            {
                list1 = grid.Read<T1>().ToList();
                if (typeof(T2) != typeof(NoResult))
                {
                    list2 = grid.Read<T2>().ToList();
                }
                if (typeof(T3) != typeof(NoResult))
                {
                    list3 = grid.Read<T3>().ToList();
                }

                return Tuple.Create(list1, list2, list3);
            }
        }
        finally { if (needsDisposed) sqlConnection.Dispose(); }
    }


    public static void ExecuteNonQuery(SqlConnection sqlConnection, string sql, object param, int? timeout = null)
    {
        bool needsDisposed = false;

        if (sqlConnection == null)
        {
            sqlConnection = new SqlConnection(SqlConnectionString);
            sqlConnection.Open();
            needsDisposed = true;
        }

        try { sqlConnection.Execute(sql, param, commandTimeout: timeout); }
        finally { if (needsDisposed) sqlConnection.Dispose(); }
    }
}

用多个输出包装多个查询

Wrapping multiple queries with multiple outputs

c#

sql

generics

refactoring

dapper