不过仔细看测试2.1的测试代码，发现循环体内包含了创建 DbContext 的代码，我在想会不会是因为多次创建 DbContext 而导致 EF 如此慢？如果把创建 DbContext 的代码放到循环体外 EF 会不会更好点？于是就有了测试2.2。

测试2.2：

LoopQueryTestWithNotCreateDbContext { static int takeCount = 1; static int queryCount = 20000; GCMemoryTest() { /* * 内存分配测试通过 vs 自带诊断与分析工具测，vs --> 分析 --> 性能与诊断 --> 内存使用率。 * 每次运行程序只能调用下面中的一个方法，不能同时调用 */ EFSqlQueryTest(takeCount, queryCount); } SpeedTest() { long useTime = 0; //预热 ChloeQueryTest(1, 1); useTime = SW.Do(() => { ChloeQueryTest(takeCount, queryCount); }); Console.WriteLine("ChloeQueryTest 执行{0}次查询总用时：{1}ms", queryCount, useTime); GC.Collect(); useTime = SW.Do(() => { ChloeSqlQueryTest(takeCount, queryCount); }); Console.WriteLine("ChloeSqlQueryTest 执行{0}次查询总用时：{1}ms", queryCount, useTime); GC.Collect(); //预热 DapperQueryTest(1, 1); useTime = SW.Do(() => { DapperQueryTest(takeCount, queryCount); }); Console.WriteLine("DapperQueryTest 执行{0}次查询总用时：{1}ms", queryCount, useTime); GC.Collect(); //预热 EFLinqQueryTest(1, 1); useTime = SW.Do(() => { EFLinqQueryTest(takeCount, queryCount); }); Console.WriteLine("EFLinqQueryTest 执行{0}次查询总用时：{1}ms", queryCount, useTime); GC.Collect(); //预热 EFSqlQueryTest(1, 1); useTime = SW.Do(() => { EFSqlQueryTest(takeCount, queryCount); }); Console.WriteLine("EFSqlQueryTest 执行{0}次查询总用时：{1}ms", queryCount, useTime); GC.Collect(); Console.WriteLine("GAME OVER"); Console.ReadKey(); } static void ChloeQueryTest(int takeCount, int loops) { using (MsSqlContext context = new MsSqlContext(DbHelper.ConnectionString)) { for (int i = 0; i < loops; i++) { int id = 0; var list = context.Query<TestEntity>().Where(a => a.Id > id).Take(takeCount).ToList(); } } } static void ChloeSqlQueryTest(int takeCount, int loops) { using (MsSqlContext context = new MsSqlContext(DbHelper.ConnectionString)) { for (int i = 0; i < loops; i++) { int id = 0; var list = context.SqlQuery<TestEntity>(string.Format("select top {0} * from TestEntity where Id>@Id", takeCount.ToString()), DbParam.Create("@Id", id)).ToList(); } } } static void DapperQueryTest(int takeCount, int loops) { using (IDbConnection conn = DbHelper.CreateConnection()) { for (int i = 0; i < loops; i++) { int id = 0; var list = conn.Query<TestEntity>(string.Format("select top {0} * from TestEntity where Id>@Id", takeCount.ToString()), new { Id = id }).ToList(); } } } static void EFLinqQueryTest(int takeCount, int loops) { using (EFContext efContext = new EFContext()) { for (int i = 0; i < loops; i++) { int id = 0; var list = efContext.TestEntity.AsNoTracking().Where(a => a.Id > id).Take(takeCount).ToList(); } } } static void EFSqlQueryTest(int takeCount, int loops) { using (EFContext efContext = new EFContext()) { for (int i = 0; i < loops; i++) { int id = 0; var list = efContext.Database.SqlQuery<TestEntity>(string.Format("select top {0} * from TestEntity where Id>@Id", takeCount.ToString()), new SqlParameter("@Id", id)).ToList(); } } } }

View Code

运行5次，得到以下结果：

 

ChloeQueryTest(ms)

ChloeSqlQueryTest(ms)

DapperQueryTest(ms)

EFLinqQueryTest(ms)

EFSqlQueryTest(ms)

第1轮

15281

11858

11981

31394

19309

第2轮

15194

12177

12314

31464

18161

第3轮

15967

12348

12366

31082

18030

第4轮

15371

11793

12479

32314

18356

第5轮

15350

11921

11937

35023

18356

平均

15411

12019

12215

32255

18442

 

GC 情况：

 

ChloeQueryTest

ChloeSqlQueryTest

DapperQueryTest

EFLinqQueryTest

EFSqlQueryTest

GC回收次数

111

41

47

368

205