官方和老人言，asp.net core中尽量用异步，为什么呢？接下来是个小demo，看看同步异步的差别吧，或许通过这个demo，就明白官方和老人的良苦用心了。

1、创建一个sql server的表

CREATE TABLE [dbo].[Students](  [StuNo] [varchar](50) NOT NULL,  [Name] [varchar](50) NULL,  [CardID] [varchar](18) NULL,  [Sex] [varchar](4) NULL,  [Birthday] [datetime] NULL,  [ClassID] [int] NULL, CONSTRAINT [PK_dbo.Students] PRIMARY KEY CLUSTERED (  [StuNo] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]GO

2、创建一个asp.net core api项目，5.0的

using Microsoft.AspNetCore.Mvc;using Microsoft.Data.SqlClient;using Microsoft.Extensions.Logging;using System;using System.Threading.Tasks;namespace AsyncWebAPI.Controllers{    [ApiController]    [Route("[controller]")]    public class StudentController : ControllerBase    {        private readonly ILogger
    
      _logger;        public StudentController(ILogger
     
       logger)        {            _logger = logger;        }        [HttpDelete("/deleteall")]        public bool DeleteAll()        {            _logger.LogInformation("删除全部");            using var con = new SqlConnection("server=.;database=TestManageDB;uid=sa;pwd=sa;");            var sql = @"delete from  [dbo].[Students]";            var cmd = new SqlCommand(sql, con);            con.Open();            var result = cmd.ExecuteNonQuery();            con.Close();            return true;        }        [HttpPost("/addstudent")]        public Student AddEntity([FromBody] Student student)        {            _logger.LogInformation("同步添加");            return SavaEntity(student);        }        Student SavaEntity(Student student)        {            student.StuNo = Guid.NewGuid().ToString();            using var con = new SqlConnection("server=.;database=TestManageDB;uid=sa;pwd=sa;");            var sql = @"INSERT INTO [dbo].[Students]           ([StuNo]           ,[Name]           ,[CardID]           ,[Sex]           ,[Birthday]           ,[ClassID]           )     VALUES           (@StuNo           ,@Name           ,@CardID           ,@Sex           ,@Birthday           ,@ClassID           )";            var cmd = new SqlCommand(sql, con);            cmd.Parameters.Add(new SqlParameter { ParameterName = "@StuNo", Value = student.StuNo, SqlDbType = System.Data.SqlDbType.VarChar });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@Name", Value = student.Name, SqlDbType = System.Data.SqlDbType.VarChar });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@CardID", Value = student.CardID, SqlDbType = System.Data.SqlDbType.VarChar });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@Sex", Value = student.Sex, SqlDbType = System.Data.SqlDbType.VarChar });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@Birthday", Value = student.Birthday, SqlDbType = System.Data.SqlDbType.DateTime });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@ClassID", Value = student.ClassID, SqlDbType = System.Data.SqlDbType.Int });            con.Open();            var result = cmd.ExecuteNonQuery();            con.Close();            return student;        }        [HttpPost("/addstudentasync")]        public async Task
      
        AddEntityAsync([FromBody] Student student)        {            _logger.LogInformation("异步添加");            return await SavaEntityAsync(student);        }        async Task
       
         SavaEntityAsync(Student student)        {            student.StuNo = Guid.NewGuid().ToString();            using var con = new SqlConnection("server=.;database=TestManageDB;uid=sa;pwd=sa;");            var sql = @"INSERT INTO [dbo].[Students]           ([StuNo]           ,[Name]           ,[CardID]           ,[Sex]           ,[Birthday]           ,[ClassID]           )     VALUES           (@StuNo           ,@Name           ,@CardID           ,@Sex           ,@Birthday           ,@ClassID           )";            var cmd = new SqlCommand(sql, con);            cmd.Parameters.Add(new SqlParameter { ParameterName = "@StuNo", Value = student.StuNo, SqlDbType = System.Data.SqlDbType.VarChar });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@Name", Value = student.Name, SqlDbType = System.Data.SqlDbType.VarChar });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@CardID", Value = student.CardID, SqlDbType = System.Data.SqlDbType.VarChar });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@Sex", Value = student.Sex, SqlDbType = System.Data.SqlDbType.VarChar });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@Birthday", Value = student.Birthday, SqlDbType = System.Data.SqlDbType.DateTime });            cmd.Parameters.Add(new SqlParameter { ParameterName = "@ClassID", Value = student.ClassID, SqlDbType = System.Data.SqlDbType.Int });            await con.OpenAsync();            var result = await cmd.ExecuteNonQueryAsync();            await con.CloseAsync();            return student;        }    }    public class Student    {        public string StuNo { get; set; }        public string Name { get; set; }        public string CardID { get; set; }        public string Sex { get; set; }        public DateTime Birthday { get; set; }        public int ClassID { get; set; }    }}
       
      
     
    

3、创建一个控制台程序，了是.net core 5.0的

using Newtonsoft.Json;using System;using System.Net.Http;using System.Text;using System.Threading.Tasks;namespace AsyncRquestClient{    class ProgramAsync    {        static int times = 100;        static async Task Main(string[] args)        {            while (true)            {                Console.WriteLine("输入循环次数");                times = int.Parse(Console.ReadLine());                #region 同步                Console.WriteLine("-----------------同步调同步API------------------");                SyncCallSyncAPI();                Console.ReadLine();                Console.WriteLine("-----------------同步调异步API------------------");                SyncCallAsyncAPI();                Console.ReadLine();                Console.WriteLine("-----------------TaskFactory同步调同步API------------------");                TaskFactorySyncCallSyncAPI();                Console.ReadLine();                Console.WriteLine("-----------------TaskFactory同步调异步API------------------");                TaskFactorySyncCallAsyncAPI();                Console.ReadLine();                #endregion                             #region 异步                Console.WriteLine("-----------------异步调异步API------------------");                await AsyncCallAsyncAPI();                Console.ReadLine();                Console.WriteLine("-----------------异步调同步API------------------");                await AsyncCallSyncAPI();                Console.ReadLine();                            Console.WriteLine("-----------------TaskFactory异步调异步API------------------");                await TaskFactoryAsyncCallAsyncAPI();                Console.ReadLine();                Console.WriteLine("-----------------TaskFactory异步调同步API------------------");                await TaskFactoryAsyncCallSyncAPI();                Console.ReadLine();                #endregion            }        }        #region 异常        /// 
        /// 异步调异步API        /// 
        /// 
            async static Task AsyncCallAsyncAPI()        {            var r = DeleteAllAsync().Result;            Console.WriteLine($"异步调异步API开始时间：{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.ffff")}");            for (int i = 1; i <= times; i++)            {                try                {                    var student = new Student { Name = "张三" + i, Birthday = DateTime.Now, CardID = "C0000" + i, ClassID = 1, Sex = "男" };                    using var client = new HttpClient();                    client.BaseAddress = new Uri("https://localhost:5001");                    var request = new HttpRequestMessage(HttpMethod.Post, "addstudentasync");                    request.Content = new StringContent(JsonConvert.SerializeObject(student), Encoding.UTF8, "application/json");                    var response = await client.SendAsync(request);                    if (response.IsSuccessStatusCode)                    {                        var content = await response.Content.ReadAsStringAsync();                        var stu = JsonConvert.DeserializeObject
    
     (content);                    }                    else                    {                        var content = response.Content.ReadAsStringAsync().Result;                        Console.WriteLine("同步调同步添加错误返回值：" + content);                    }                }                catch (Exception exc)                {                    Console.WriteLine(exc.Message);                }            }        }        /// 
     
        /// TaskFactory异步调异步API        /// 
        /// 
             static async Task TaskFactoryAsyncCallAsyncAPI()        {            var r = await DeleteAllAsync();            Console.WriteLine($"TaskFactory异步调异步开API始时间：{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.ffff")}");            for (int i = 1; i <= times; i++)            {                await Task.Factory.StartNew(async () =>                {                    try                    {                        var student = new Student { Name = "张三" + i, Birthday = DateTime.Now, CardID = "C0000" + i, ClassID = 1, Sex = "男" };                        using var client = new HttpClient();                        client.BaseAddress = new Uri("https://localhost:5001");                        var request = new HttpRequestMessage(HttpMethod.Post, "addstudentasync");                        request.Content = new StringContent(JsonConvert.SerializeObject(student), Encoding.UTF8, "application/json");                        var response = await client.SendAsync(request);                        if (response.IsSuccessStatusCode)                        {                            var content = await response.Content.ReadAsStringAsync();                            var stu = JsonConvert.DeserializeObject
     
      (content);                        }                        else                        {                            var content = await response.Content.ReadAsStringAsync();                            Console.WriteLine("异步调异步添加错误返回值：" + content);                        }                    }                    catch (Exception exc)                    {                        Console.WriteLine(exc.Message);                    }                });            }        }        /// 
      
        /// 异步调同步API        /// 
        /// 
              async static Task AsyncCallSyncAPI()        {            var r = DeleteAllAsync().Result;            Console.WriteLine($"异步调同步API开始时间：{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.ffff")}");            for (int i = 1; i <= times; i++)            {                try                {                    var student = new Student { Name = "张三" + i, Birthday = DateTime.Now, CardID = "C0000" + i, ClassID = 1, Sex = "男" };                    using var client = new HttpClient();                    client.BaseAddress = new Uri("https://localhost:5001");                    var request = new HttpRequestMessage(HttpMethod.Post, "addstudent");                    request.Content = new StringContent(JsonConvert.SerializeObject(student), Encoding.UTF8, "application/json");                    var response = await client.SendAsync(request);                    if (response.IsSuccessStatusCode)                    {                        var content = await response.Content.ReadAsStringAsync();                        var stu = JsonConvert.DeserializeObject
      
       (content);                    }                    else                    {                        var content = response.Content.ReadAsStringAsync().Result;                        Console.WriteLine("同步调同步添加错误返回值：" + content);                    }                }                catch (Exception exc)                {                    Console.WriteLine(exc.Message);                }            }        }        /// 
       
        /// TaskFactory异步调同步API        /// 
        /// 
               static async Task TaskFactoryAsyncCallSyncAPI()        {            var r = await DeleteAllAsync();            Console.WriteLine($"TaskFactory异步调同步API开始时间：{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.ffff")}");            for (int i = 1; i <= times; i++)            {                await Task.Factory.StartNew(async () =>                {                    try                    {                        var student = new Student { Name = "张三" + i, Birthday = DateTime.Now, CardID = "C0000" + i, ClassID = 1, Sex = "男" };                        using var client = new HttpClient();                        client.BaseAddress = new Uri("https://localhost:5001");                        var request = new HttpRequestMessage(HttpMethod.Post, "addstudent");                        request.Content = new StringContent(JsonConvert.SerializeObject(student), Encoding.UTF8, "application/json");                        var response = await client.SendAsync(request);                        if (response.IsSuccessStatusCode)                        {                            var content = await response.Content.ReadAsStringAsync();                            var stu = JsonConvert.DeserializeObject
       
        (content);                        }                        else                        {                            var content = await response.Content.ReadAsStringAsync();                            Console.WriteLine("异步调异步添加错误返回值：" + content);                        }                    }                    catch (Exception exc)                    {                        Console.WriteLine(exc.Message);                    }                });            }        }        #endregion        #region 同步        /// 
        
        /// 同步调同步API        /// 
        static void SyncCallSyncAPI()        {            var r = DeleteAllAsync().Result;            Console.WriteLine($"同步调同步开始时间：{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.ffff")}");            for (int i = 1; i <= times; i++)            {                try                {                    var student = new Student { Name = "张三" + i, Birthday = DateTime.Now, CardID = "C0000" + i, ClassID = 1, Sex = "男" };                    using var client = new HttpClient();                    client.BaseAddress = new Uri("https://localhost:5001");                    var request = new HttpRequestMessage(HttpMethod.Post, "addstudent");                    request.Content = new StringContent(JsonConvert.SerializeObject(student), Encoding.UTF8, "application/json");                    var response = client.SendAsync(request).Result;                    if (response.IsSuccessStatusCode)                    {                        var content = response.Content.ReadAsStringAsync().Result;                        var stu = JsonConvert.DeserializeObject
        
         (content);                    }                    else                    {                        var content = response.Content.ReadAsStringAsync().Result;                        Console.WriteLine("同步调同步添加错误返回值：" + content);                    }                }                catch (Exception exc)                {                    Console.WriteLine(exc.Message);                }            }        }        static void TaskFactorySyncCallSyncAPI()        {            var r = DeleteAllAsync().Result;            Console.WriteLine($"TaskFactory异步调同步API开始时间：{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.ffff")}");            for (int i = 1; i <= times; i++)            {                var result = Task.Factory.StartNew(async () =>                  {                      try                      {                          var student = new Student { Name = "张三" + i, Birthday = DateTime.Now, CardID = "C0000" + i, ClassID = 1, Sex = "男" };                          using var client = new HttpClient();                          client.BaseAddress = new Uri("https://localhost:5001");                          var request = new HttpRequestMessage(HttpMethod.Post, "addstudent");                          request.Content = new StringContent(JsonConvert.SerializeObject(student), Encoding.UTF8, "application/json");                          var response = await client.SendAsync(request);                          if (response.IsSuccessStatusCode)                          {                              var content = await response.Content.ReadAsStringAsync();                              var stu = JsonConvert.DeserializeObject
         
          (content); } else { var content = await response.Content.ReadAsStringAsync(); Console.WriteLine("异步调异步添加错误返回值：" + content); } } catch (Exception exc) { Console.WriteLine(exc.Message); } }).Result; } } /// 
          
 /// 同步调异步API /// 
 static void SyncCallAsyncAPI() { var r = DeleteAllAsync().Result; Console.WriteLine($"同步调异步开始时间：{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.ffff")}"); for (int i = 1; i <= times; i++) { try { var student = new Student { Name = "张三" + i, Birthday = DateTime.Now, CardID = "C0000" + i, ClassID = 1, Sex = "男" }; using var client = new HttpClient(); client.BaseAddress = new Uri("https://localhost:5001"); var request = new HttpRequestMessage(HttpMethod.Post, "addstudentasync"); request.Content = new StringContent(JsonConvert.SerializeObject(student), Encoding.UTF8, "application/json"); var response = client.SendAsync(request).Result; if (response.IsSuccessStatusCode) { var content = response.Content.ReadAsStringAsync().Result; var stu = JsonConvert.DeserializeObject
          
           (content); } else { var content = response.Content.ReadAsStringAsync().Result; Console.WriteLine("同步调异步添加错误返回值：" + content); } } catch (Exception exc) { Console.WriteLine(exc.Message); } } } static void TaskFactorySyncCallAsyncAPI() { var r = DeleteAllAsync().Result; Console.WriteLine($"TaskFactory异步调同步API开始时间：{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.ffff")}"); for (int i = 1; i <= times; i++) { var result = Task.Factory.StartNew(async () => { try { var student = new Student { Name = "张三" + i, Birthday = DateTime.Now, CardID = "C0000" + i, ClassID = 1, Sex = "男" }; using var client = new HttpClient(); client.BaseAddress = new Uri("https://localhost:5001"); var request = new HttpRequestMessage(HttpMethod.Post, "addstudentasync"); request.Content = new StringContent(JsonConvert.SerializeObject(student), Encoding.UTF8, "application/json"); var response = await client.SendAsync(request); if (response.IsSuccessStatusCode) { var content = await response.Content.ReadAsStringAsync(); var stu = JsonConvert.DeserializeObject
           
            (content); } else { var content = await response.Content.ReadAsStringAsync(); Console.WriteLine("异步调异步添加错误返回值：" + content); } } catch (Exception exc) { Console.WriteLine(exc.Message); } }).Result; } } #endregion static async Task
            
              DeleteAllAsync() { using var client = new HttpClient(); client.BaseAddress = new Uri("https://localhost:5001"); var request = new HttpRequestMessage(HttpMethod.Delete, "deleteall"); var response = await client.SendAsync(request); if (response.IsSuccessStatusCode) { var content = await response.Content.ReadAsStringAsync(); var result = JsonConvert.DeserializeObject
             
              (content); return result; } else { var content = await response.Content.ReadAsStringAsync(); Console.WriteLine("删除错误返回值：" + content); return false; } } } public class Student { public string StuNo { get; set; } public string Name { get; set; } public string CardID { get; set; } public string Sex { get; set; } public DateTime Birthday { get; set; } public int ClassID { get; set; } }}
             
            
           
          
         
        
       
      
     
    

4、在sql查询分析器中用这里的语句采集结果

--检查记录数是否完整select count(*) from students;--查询时间隔select datediff(millisecond,(select min(birthday) as mi from students),(select max(birthday) as ma from students));

结果如下：

客户端调用，异步优势明显；在所有的调用中，服务端的同步要优于异步。