Question

我是EF的新手，我正在尝试一些非常基本的东西。在一个全新的控制台应用程序项目中，我只使用了＆＃34;反向工程师代码优先＆＃34; （来自Entity Framework Power Tools）在db（本地到我的机器上）。

然后我修改了Main以进行一些基本测试...从一个表中读取相同的三行两次...一次使用EF，一次使用传统系统（SqlConnection，DataReader等）我计时两个系统，并以微秒为单位打印输出时间。

当它运行时，我得到以下内容（当然略有变化）：

EF query 1: 5540 (slow, but startup...perhaps expected.)
EF query 2: 907 (What?  Why so slow?)
EF query 3: 910 
Trad query 1: 0 (Fast, even though I'm creating a new connection each time)
Trad query 2: 0
Trad query 3: 0

我做错了什么吗？我的LINQ查询是否在某种程度上搞砸了并且无可救药地效率低下，或者EF出于某种原因真的很慢？

代码：

    static void Main(string[] args)
    {
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.Start();

        // EF Path
        // Selecting three rows, one at a time
        using (var context = new myCustomContext())
        {
            var query = from b in context.myTable
                        where b.KEY == "Key1"
                        select b;

            stopwatch.Stop();

            foreach (var returnedVal in query)
            {
                Console.WriteLine("EF query 1: " + stopwatch.ElapsedMilliseconds);
            }

            stopwatch.Restart();

            var query2 = from b in context.myTable
                         where b.KEY == "Key2"
                         select b;

            foreach (var returnedVal in query2)
            {
                Console.WriteLine("EF query 2: " + stopwatch.ElapsedMilliseconds);
            }

            stopwatch.Restart();

            var query3 = from b in context.myTable
                         where b.KEY == "Key3"
                         select b;

            foreach (var returnedVal in query3)
            {
                Console.WriteLine("EF query 3: " + stopwatch.ElapsedMilliseconds);
            }
        }

        // Traditional path
        // Selecting same three rows, one at a time.  I recreate a connection
        // each time, in a futile attempt to even the odds.
        string connectionString = "<myConnectionString>";

        stopwatch.Restart();

        using (SqlConnection con = new SqlConnection(connectionString))
        {
            con.Open();

            using (SqlCommand command = new SqlCommand("select * from myTable where KEY = 'Key1'", con))
            using (SqlDataReader reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    Console.WriteLine("Trad query 1: " + stopwatch.ElapsedMilliseconds);
                }
            }
        }

        using (SqlConnection con = new SqlConnection(connectionString))
        {
            con.Open();
            stopwatch.Restart();

            using (SqlCommand command = new SqlCommand("select * from myTable where KEY = 'Key2'", con))
            using (SqlDataReader reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    Console.WriteLine("Trad query 2: " + stopwatch.ElapsedMilliseconds);
                }
            }

            stopwatch.Restart();
        }

        using (SqlConnection con = new SqlConnection(connectionString))
        {
            con.Open();
            using (SqlCommand command = new SqlCommand("select * from myTable where KEY = 'Key3'", con))
            using (SqlDataReader reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    Console.WriteLine("Trad query 3: " + stopwatch.ElapsedMilliseconds);
                }
            }
        }

        Console.ReadLine();
    }

EF真的很慢，还是我做错了什么？

0 个答案: