精致和匿名的类型

Question

是否可以使用Dapper的匿名类型？

我可以看到你如何使用动态ie

connection.Query<dynamic>(blah, blah, blah) 

然后可以做一个

.Select(p=> new { A, B ,C }) 

或之后的一些变化？

编辑

我想我会告诉你我现在如何使用Dapper.我倾向于缓存(使用InMemoryCache)数据,所以我只是在开头做一个大查询(使用Dapper超级快)然后我使用Linq在我的存储库中对它进行排序.

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data.Common;
using System.Linq;
using Dapper;

namespace SomeNamespace.Data
{
public class DapperDataContext : IDisposable
{
    private readonly string _connectionString;
    private readonly DbProviderFactory _provider;
    private readonly string _providerName;

    public DapperDataContext()
    {
        const string connectionStringName = " DataContextConnectionString";
        _connectionString = ConfigurationManager.ConnectionStrings[connectionStringName].ConnectionString;
        _providerName = ConfigurationManager.ConnectionStrings[connectionStringName].ProviderName;
        _provider = DbProviderFactories.GetFactory(_providerName);
    }

    public IEnumerable<MyDataView> MyData1 { get; private set; }
    public IEnumerable<MyDataView> MyData2 { get; private set; }

    protected string SqlSelectMyTable1Query
    {
        get
        {
            return @"SELECT Id, A, B, C from table1Name";
        }
    }   


protected string SqlSelectMyTable2Query
{
    get
    {
    return @"SELECT Id, A, B, C from table2Name";
    }
    }

    public void Dispose()
    {
    }

    public void Refresh()
    {
        using (var connection = _provider.CreateConnection())
        {
            // blow up if null
            connection.ConnectionString = _connectionString;
            connection.Open();

            var sql = String.Join(" ",
                            new[]
                                {
                                    SqlSelectMyTable1Query,
                                    SqlSelectMyTable2Query
                                });

            using (var multi = connection.QueryMultiple(sql))
            {
                MyData1 = multi.Read<MyDataView>().ToList();
                MyData2 = multi.Read<MyDataView>().ToList();
            }
        }
    }

    public class MyDataView
    {
        public long Id { get; set; }
        public string A { get; set; }
        public string B { get; set; }
        public string C { get; set; }
    }      
}
}

InMemoryCache看起来像这样

namespace Libs.Web
{
public class InMemoryCache : ICacheService
{
    #region ICacheService Members

    public T Get<T>(string cacheId, Func<T> getItemCallback) where T : class
    {
        var item = HttpRuntime.Cache.Get(cacheId) as T;
        if (item == null)
        {
            item = getItemCallback();
            HttpContext.Current.Cache.Insert(cacheId, item);
        }
        return item;
    }

    public void Clear(string cacheId)
    {
        HttpContext.Current.Cache.Remove(cacheId);
    }

    #endregion
}

public interface ICacheService
{
    T Get<T>(string cacheId, Func<T> getItemCallback) where T : class;
    void Clear(string cacheId);
}
}

Answer 1

是否可以使用Dapper的匿名类型？

当然看到非泛型的Query覆盖,它返回一个动态,IDictionary<string, object>这个对象是一个expando,可以使用点表示法进行强制转换或访问.

例如:

var v = connection.Query("select 1 as a, 2 as b").First(); 
Console.Write("{0} {1}",v.a, v.b) // prints: 1 2

然后可以做一个 .Select

当然,你得到了IEnumerable<dynamic>......你可以运行你想要的任何东西.

Answer 2

这是使用dapper的匿名类型的另一种解决方案:

public static class DapperExtensions
{
    public static IEnumerable<T> Query<T>(this IDbConnection connection, Func<T> typeBuilder, string sql)
    {
        return connection.Query<T>(sql);
    }
}

并像这样使用它:

var data = connection.Query(() => new 
{
    ContactId = default(int),
    Name = default(string),
}, "SELECT ContactId, Name FROM Contact");

Answer 3

只是 Guillaume86 的伟大解决方案的一个小改进：

public static IEnumerable<T> Query<T>(this IDbConnection connection, Func<T> typeBuilder,
    string sql, dynamic param = null, IDbTransaction transaction = null,
    bool buffered = true, int? commandTimeout = null, CommandType? commandType = null)
{
    return SqlMapper.Query<T>(connection, sql, param, transaction, buffered,
        commandTimeout, commandType);
}

Answer 4

另一种方法是使用作为 C# 7.0 的一部分添加的元组类型

var users = dbConnection
    .Query<(Guid UserId, string Username)>("SELECT UserId, Username From MyUsers")
    .AsList();