.NET Core隨筆把數據庫數據查出來轉JSON並輸出

直接建立WEB項目便可；

  public class Startup
    {
        //startup.cs是站點啓動時具體作了哪些事情，主要是開啓了一個mvc服務。
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.Configure<CookiePolicyOptions>(options =>
            {
                // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
            });

            services.AddSession();

            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();   //若是不添加將致使樣式文件不能被客戶端加載
            app.UseCookiePolicy();
            app.UseSession();

            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");
            }
                );
        }
    }

建立一個DB類用於查數據：

 public class DB : DbContext
    {
        public DB()
        {   //若是沒有數據庫，自動建立，有了什麼都不幹
            Database.EnsureCreated();
        }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {    //對於這個上下文重寫此方法以配置要使用的數據庫（和其餘選項）。對於上下文的每一個實例調用此方法建立。

            //加載appsetting.json
            IConfiguration configuration = new ConfigurationBuilder()
                 .SetBasePath(Directory.GetCurrentDirectory())
              .AddJsonFile("appsettings.json").Build();

            string connectionString = configuration["DBSetting:ConnectString"];
            optionsBuilder.UseSqlServer(connectionString);

            base.OnConfiguring(optionsBuilder);
        }

        public DbSet<studen> studen { set; get; }

        public DbSet<xx> xx { set; get; }

    }
    //原文：https://blog.csdn.net/weixin_41609327/article/details/80821798 

appsettings.json 

{
  "Logging": {
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "DBSetting": {
    "ConnectString": "server=.;database=test_core;uid=sa;pwd=123"

  },
  "AllowedHosts": "*"
}

有DB類確定少不了help類

  /// 此類爲抽象類，
    /// 不容許實例化，在應用時直接調用便可
    /// </summary>
    //  abstract   抽象類標識
    public abstract class SqlHelper
    {
        //加載appsetting.json
        static IConfiguration configuration = new ConfigurationBuilder()
              .SetBasePath(Directory.GetCurrentDirectory())
             .AddJsonFile("appsettings.json").Build();    


        /// <summary>
       /// 數據庫鏈接字符串
       /// </summary>
        private static readonly string connectionString = configuration["DBSetting:ConnectString"];   //獲取DBSetting下的ConnectString值
        private static Hashtable parmCache = Hashtable.Synchronized(new Hashtable()); 

        #region//ExecteNonQuery方法

        /// <summary>
        ///執行一個不須要返回值的SqlCommand命令，經過指定專用的鏈接字符串。
        /// 使用參數數組形式提供參數列表 
        /// </summary>
        /// <param name="connectionString">一個有效的數據庫鏈接字符串</param>
        /// <param name="cmdType">SqlCommand命令類型 (存儲過程， T-SQL語句， 等等。)</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個數值表示此SqlCommand命令執行後影響的行數</returns>
        public static int ExecteNonQuery(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        { 
            //       =執行SQL語句    
            SqlCommand cmd = new SqlCommand();
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                //經過PrePareCommand方法將參數逐個加入到SqlCommand的參數集合中
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                int val = cmd.ExecuteNonQuery();
                //清空SqlCommand中的參數列表
                cmd.Parameters.Clear();
                return val;
            }
        }

        /// <summary>
        ///執行一個不須要返回值的SqlCommand命令，經過指定專用的鏈接字符串。
        /// 使用參數數組形式提供參數列表 
        /// </summary>
        /// <param name="cmdType">SqlCommand命令類型 (存儲過程， T-SQL語句， 等等。)</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個數值表示此SqlCommand命令執行後影響的行數</returns>
        public static int ExecteNonQuery(CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecteNonQuery(connectionString, cmdType, cmdText, commandParameters);
        }

        /// <summary>
        ///存儲過程專用
        /// </summary>
        /// <param name="cmdText">存儲過程的名字</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個數值表示此SqlCommand命令執行後影響的行數</returns>
        public static int ExecteNonQueryProducts(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecteNonQuery(CommandType.StoredProcedure, cmdText, commandParameters);
        }

        /// <summary>
        ///Sql語句專用
        /// </summary>
        /// <param name="cmdText">T_Sql語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個數值表示此SqlCommand命令執行後影響的行數</returns>
        public static int ExecteNonQueryText(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecteNonQuery(CommandType.Text, cmdText, commandParameters);
        }

        #endregion
        #region//GetTable方法

        /// <summary>
        /// 執行一條返回結果集的SqlCommand，經過一個已經存在的數據庫鏈接
        /// 使用參數數組提供參數
        /// </summary>
        /// <param name="connecttionString">一個現有的數據庫鏈接</param>
        /// <param name="cmdTye">SqlCommand命令類型</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個表集合(DataTableCollection)表示查詢獲得的數據集</returns>
        public static DataTableCollection GetTable(string connecttionString, CommandType cmdTye, string cmdText, SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            DataSet ds = new DataSet();
            using (SqlConnection conn = new SqlConnection(connecttionString))
            {
                PrepareCommand(cmd, conn, null, cmdTye, cmdText, commandParameters);
                SqlDataAdapter adapter = new SqlDataAdapter();
                adapter.SelectCommand = cmd;
                adapter.Fill(ds);
            }
            DataTableCollection table = ds.Tables;
            return table;
        }

        /// <summary>
        /// 執行一條返回結果集的SqlCommand，經過一個已經存在的數據庫鏈接
        /// 使用參數數組提供參數
        /// </summary>
        /// <param name="cmdTye">SqlCommand命令類型</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個表集合(DataTableCollection)表示查詢獲得的數據集</returns>
        public static DataTableCollection GetTable(CommandType cmdTye, string cmdText, SqlParameter[] commandParameters)
        {
            return GetTable(connectionString, cmdTye, cmdText, commandParameters);
        }


        /// <summary>
        /// 執行存儲過程專用
        /// </summary>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個表集合(DataTableCollection)表示查詢獲得的數據集</returns>
        public static DataTableCollection GetTableProducts(string cmdText, SqlParameter[] commandParameters)
        {
            return GetTable(CommandType.StoredProcedure, cmdText, commandParameters);
        }

        /// <summary>
        /// 執行Sql語句專用
        /// </summary>
        /// <param name="cmdText"> T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個表集合(DataTableCollection)表示查詢獲得的數據集</returns>
        public static DataTableCollection GetTableText(string cmdText, SqlParameter[] commandParameters)
        {
            return GetTable(CommandType.Text, cmdText, commandParameters);
        }
        #endregion


        /// <summary>
        /// 爲執行命令準備參數
        /// </summary>
        /// <param name="cmd">SqlCommand 命令</param>
        /// <param name="conn">已經存在的數據庫鏈接</param>
        /// <param name="trans">數據庫事物處理</param>
        /// <param name="cmdType">SqlCommand命令類型 (存儲過程， T-SQL語句， 等等。)</param>
        /// <param name="cmdText">Command text，T-SQL語句 例如 Select * from Products</param>
        /// <param name="cmdParms">返回帶參數的命令</param>
        private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, CommandType cmdType, string cmdText, SqlParameter[] cmdParms)
        {
            //判斷數據庫鏈接狀態
            if (conn.State != ConnectionState.Open)
                conn.Open();
            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            //判斷是否須要事物處理
            if (trans != null)
                cmd.Transaction = trans;
            cmd.CommandType = cmdType;
            if (cmdParms != null)
            {
                foreach (SqlParameter parm in cmdParms)
                    cmd.Parameters.Add(parm);
            }
        }

        /// <summary>
        /// Execute a SqlCommand that returns a resultset against the database specified in the connection string 
        /// using the provided parameters.
        /// </summary>
        /// <param name="connectionString">一個有效的數據庫鏈接字符串</param>
        /// <param name="cmdType">SqlCommand命令類型 (存儲過程， T-SQL語句， 等等。)</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>A SqlDataReader containing the results</returns>
        public static SqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            SqlConnection conn = new SqlConnection(connectionString);
            // we use a try/catch here because if the method throws an exception we want to 
            // close the connection throw code, because no datareader will exist, hence the 
            // commandBehaviour.CloseConnection will not work
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return rdr;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }
        #region//ExecuteDataSet方法

        /// <summary>
        /// return a dataset
        /// </summary>
        /// <param name="connectionString">一個有效的數據庫鏈接字符串</param>
        /// <param name="cmdType">SqlCommand命令類型 (存儲過程， T-SQL語句， 等等。)</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>return a dataset</returns>
        public static DataSet ExecuteDataSet(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlConnection conn = new SqlConnection(connectionString);
            SqlCommand cmd = new SqlCommand();
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                SqlDataAdapter da = new SqlDataAdapter();
                DataSet ds = new DataSet();
                da.SelectCommand = cmd;
                da.Fill(ds);
                return ds;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }


        /// <summary>
        /// 返回一個DataSet
        /// </summary>
        /// <param name="cmdType">SqlCommand命令類型 (存儲過程， T-SQL語句， 等等。)</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>return a dataset</returns>
        public static DataSet ExecuteDataSet(CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteDataSet(connectionString, cmdType, cmdText, commandParameters);
        }

        /// <summary>
        /// 返回一個DataSet
        /// </summary>
        /// <param name="cmdText">存儲過程的名字</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>return a dataset</returns>
        public static DataSet ExecuteDataSetProducts(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteDataSet(connectionString, CommandType.StoredProcedure, cmdText, commandParameters);
        }

        /// <summary>
        /// 返回一個DataSet
        /// </summary>

        /// <param name="cmdText">T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>return a dataset</returns>
        public static DataSet ExecuteDataSetText(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteDataSet(connectionString, CommandType.Text, cmdText, commandParameters);
        }


        public static DataView ExecuteDataSet(string connectionString, string sortExpression, string direction, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlConnection conn = new SqlConnection(connectionString);
            SqlCommand cmd = new SqlCommand();
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                SqlDataAdapter da = new SqlDataAdapter();
                DataSet ds = new DataSet();
                da.SelectCommand = cmd;
                da.Fill(ds);
                DataView dv = ds.Tables[0].DefaultView;
                dv.Sort = sortExpression + " " + direction;
                return dv;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }
        #endregion


        #region // ExecuteScalar方法


        /// <summary>
        /// 返回第一行的第一列
        /// </summary>
        /// <param name="cmdType">SqlCommand命令類型 (存儲過程， T-SQL語句， 等等。)</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個對象</returns>
        public static object ExecuteScalar(CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteScalar(SqlHelper.connectionString, cmdType, cmdText, commandParameters);
        }

        /// <summary>
        /// 返回第一行的第一列存儲過程專用
        /// </summary>
        /// <param name="cmdText">存儲過程的名字</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個對象</returns>
        public static object ExecuteScalarProducts(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteScalar(SqlHelper.connectionString, CommandType.StoredProcedure, cmdText, commandParameters);
        }

        /// <summary>
        /// 返回第一行的第一列Sql語句專用
        /// </summary>
        /// <param name="cmdText">者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>返回一個對象</returns>
        public static object ExecuteScalarText(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteScalar(SqlHelper.connectionString, CommandType.Text, cmdText, commandParameters);
        }

        /// <summary>
        /// Execute a SqlCommand that returns the first column of the first record against the database specified in the connection string 
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">一個有效的數據庫鏈接字符串</param>
        /// <param name="cmdType">SqlCommand命令類型 (存儲過程， T-SQL語句， 等等。)</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
        public static object ExecuteScalar(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();

            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
                object val = cmd.ExecuteScalar();
                cmd.Parameters.Clear();
                return val;
            }
        }

        /// <summary>
        /// Execute a SqlCommand that returns the first column of the first record against an existing database connection 
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">一個有效的數據庫鏈接字符串</param>
        /// <param name="cmdType">SqlCommand命令類型 (存儲過程， T-SQL語句， 等等。)</param>
        /// <param name="cmdText">存儲過程的名字或者 T-SQL 語句</param>
        /// <param name="commandParameters">以數組形式提供SqlCommand命令中用到的參數列表</param>
        /// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
        public static object ExecuteScalar(SqlConnection connection, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
            object val = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            return val;
        }

        #endregion


        /// <summary>
        /// add parameter array to the cache
        /// </summary>
        /// <param name="cacheKey">Key to the parameter cache</param>
        /// <param name="cmdParms">an array of SqlParamters to be cached</param>
        public static void CacheParameters(string cacheKey, params SqlParameter[] commandParameters)
        {
            parmCache[cacheKey] = commandParameters;
        }

        /// <summary>
        /// Retrieve cached parameters
        /// </summary>
        /// <param name="cacheKey">key used to lookup parameters</param>
        /// <returns>Cached SqlParamters array</returns>
        public static SqlParameter[] GetCachedParameters(string cacheKey)
        {
            SqlParameter[] cachedParms = (SqlParameter[])parmCache[cacheKey];
            if (cachedParms == null)
                return null;
            SqlParameter[] clonedParms = new SqlParameter[cachedParms.Length];
            for (int i = 0, j = cachedParms.Length; i < j; i++)
                clonedParms[i] = (SqlParameter)((ICloneable)cachedParms[i]).Clone();
            return clonedParms;
        }
        /// <summary>
        /// 檢查是否存在
        /// </summary>
        /// <param name="strSql">Sql語句</param>
        /// <returns>bool結果</returns>
        public static bool Exists(string strSql)
        {
            int cmdresult = Convert.ToInt32(ExecuteScalar(connectionString, CommandType.Text, strSql, null));
            if (cmdresult == 0)
            {
                return false;
            }
            else
            {
                return true;
            }
        }

        /// <summary>
        /// 檢查是否存在
        /// </summary>
        /// <param name="strSql">Sql語句</param>
        /// <param name="cmdParms">參數</param>
        /// <returns>bool結果</returns>
        public static bool Exists(string strSql, params SqlParameter[] cmdParms)
        {
            int cmdresult = Convert.ToInt32(ExecuteScalar(connectionString, CommandType.Text, strSql, cmdParms));
            if (cmdresult == 0)
            {
                return false;
            }
            else
            {
                return true;
            }
        }
        
  //原文：https://blog.csdn.net/weixin_41609327/article/details/80786764 
    }

SqlHelp

public DataTable GetStuden()
        {
            string sql = "select * from studen;";
            var data = SqlHelper.GetTable(CommandType.Text,sql,new SqlParameter[] { });
            return data[0];
        }

DAL

一個保存類：

public static class save
    {
        
        public static void JsonWrite(string configpath,string str,out string name,out string filename)
        {
            //string configpath = System.AppDomain.CurrentDomain.BaseDirectory + "/json/";

            configpath = configpath + "/json/";

            if (!Directory.Exists(configpath))//若是目錄不存在就建立
            {
                Directory.CreateDirectory(configpath);
            }
            filename = configpath + "/";

            name = "Json_" + DateTime.Now.ToString("yyyy_MM_dd_HH_mm_ss_ffff") + ".json";//用日期對文件命名;     

            filename = filename + name;     //   一個  文件的 絕對路徑   out   出去  給使用
            //建立或打開文件，  AppendText 向文件末尾追加記錄
            StreamWriter mySw = File.AppendText(filename);     //      查找是否有該路徑的文件     並打開        
            string a = str;
            mySw.WriteLine(a);     //    寫入某數據

            //關閉文件
            mySw.Close();      //    關閉寫入流
        }
    }

保存文件類

到控制器下載了。

 public IActionResult Json()
        {
            using (var db = new DB())
            {
                List<studen> list =  db.studen.GroupBy(b=>new { b.Id,b.Name }).Select(b => new studen
                {
                    Id = b.Key.Id,
                    Name = b.Key.Name
                }).ToList();
                db.studen.ToList();

                var xx = db.xx.GroupBy(x => new { x.id }).Select(v => new xx
                {
                    id=v.Key.id,
                    name= v.Sum(x => x.name)
                }).ToList();
                string json = "[";
                foreach (var item in list)
                {
                    json += "{\"id\":\""+item.Id+"\",\"name\":\""+item.Name+"\" },";
                }
                json = json.Substring(0, json.Length - 1);       //刪除最後一個逗號，
                json += "]";
                //string root = Directory.GetParent(AppContext.BaseDirectory).Parent.Parent.Parent.FullName;   //Parent退到上個目錄
                string contentRootPath = _hostingEnvironment.ContentRootPath;      //    .net core獲取基目錄的用法
                string name;                                                                                    //    out   出來的是路徑加上json文件名
                string file;                                                          //    絕對路徑
                save.JsonWrite(contentRootPath, json.ToString(),out name, out file);     //寫入文件 並保存
                
                HttpContext.Session.SetString("file",file);      //   core    的   Session    就得這麼用  還得using   Microsoft.AspNetCore.Http;

                //     讀取某json文件     
                string str = "";

                using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))   //  獲取文件流
                {
                    using (StreamReader sr = new StreamReader(fs, Encoding.GetEncoding("utf-8")))   //    讀取文件流
                    {
                        str = sr.ReadToEnd().ToString();      //     獲取  文件的  所有  轉 字符串
                        sr.Close();
                    }
                    fs.Close();
                }
                    
                
               
             }
            //           new filestram   須文件的絕對路徑    獲取文件流        輸入出的文件格式         輸出的文件名稱
            return File(new FileStream(HttpContext.Session.GetString("file"), FileMode.Open), "application/octet-stream", $"導出測試{DateTime.Now.ToString("yyyy年MM月dd日HH點mm分ss秒")}.json");


            if (System.IO.File.Exists("文件的絕對路徑"))
            { //刪除文件 
                System.IO.File.Delete("文件的絕對路徑");
            }
        }

        //public IActionResult download()
        //{
        //    return File(new FileStream(HttpContext.Session.GetString("file"), FileMode.Open), "application/octet-stream", $"導出測試{DateTime.Now.ToString("yyyyMMddHHmmss")}.json");
        //}