精致和匿名类型

问题描述

是否可以在 Dapper 中使用匿名类型?

Is it possible to use anonymous types with Dapper?

我可以看到您如何使用动态，即

I can see how you can use dynamic i.e.

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

然后可以做一个

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

或者之后的一些变体?

编辑

我想我会向您展示我目前如何使用 Dapper.我倾向于缓存(使用 InMemoryCache)数据，所以我只在开始时做一个大查询(使用 Dapper 非常快)，然后我使用 Linq 在我的存储库中整理所有数据.

I thought I'd show you how I am using Dapper at the moment. I tend to cache (using an InMemoryCache) data so I just do one big query at the beginning (which is super quick using Dapper) then I use Linq to sort it all out in my Repository.

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

The InMemoryCache looks like this

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);
}
}

推荐答案

这是另一种在 dapper 中使用匿名类型的解决方案:

Here's another solution to use anonymous types with dapper:

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");

这篇关于精致和匿名类型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！