以下代碼是參考幾個不同人的寫法總結寫成的，肯定還有很大的優化空間，暫存該版本；有建議的歡迎提出；

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FirstBI
{
    public abstract class SqlHelpertrain//
 
定義為abstract抽象類，不能被實例化，在應用時直接調用
    {
        /*1.獲取數據庫連接字符串；
         * 2.Connection 鏈接綁定，open/close；
         * 3.實例化一個Command命令，給定命令執行的超時時間 ，命令執行的連接；命令的類型（增/刪/改/查）
         *      ，是否帶事務，執行用到哪些參數，還有最重要的命令執行的sql字符串；
         * 4.SqlDataAdapter承接命令返回的結果集
         */
        private static int TimeOut = 5000;
        
 
private static string connStrs = ConfigurationManager.ConnectionStrings["FirstBI.Properties.Settings.BaseERPConnectionString"].ConnectionString;
        /// <summary>
        /// 獲取SqlCommand
        /// </summary>
        /// <param name="conn"></param>
        /// <param name="cmdType"></param>
 

        /// <param name="tran"></param>
        /// <param name="sqlParams"></param>
        /// <returns></returns>
        public static SqlCommand GetSqlCommand(string sql, SqlConnection conn, CommandType cmdType, SqlTransaction tran, params SqlParameter[] sqlParams)
        {
            SqlCommand cmd = new SqlCommand(sql, conn);
            cmd.CommandTimeout = TimeOut;
            cmd.CommandType = cmdType;
            if (tran != null)
                cmd.Transaction = tran;
            if (sqlParams != null && sqlParams.Length > 0)
                cmd.Parameters.AddRange(sqlParams);
            return cmd;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="cmdType"></param>
        /// <param name="tran"></param>
        /// <param name="sqlParams"></param>
        /// <returns></returns>
        public static DataTable GetDataTable(string sql, CommandType cmdType, SqlTransaction tran, params SqlParameter[] sqlParams)
        {
            using (SqlConnection conn = new SqlConnection(connStrs))
            {
                try
                {
                    conn.Open();
                    using (SqlCommand cmd = GetSqlCommand(sql, conn, cmdType, tran, sqlParams))
                    {
                        using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                        {
                            DataTable dt = new DataTable();
                            da.Fill(dt);
                            return dt;
                        }
                    }

                }
                catch (SqlException ex)
                {
                    StringBuilder log = new StringBuilder();
                    log.Append("查詢數據錯誤：");
                    log.Append(ex);
                    throw new Exception(log.ToString());
                }
                finally
                {
                    conn.Close();
                }
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="cmdType"></param>
        /// <param name="tran"></param>
        /// <param name="sqlParams"></param>
        /// <returns></returns>
        public static DataSet GetDataSet(string sql, CommandType cmdType, SqlTransaction tran, params SqlParameter[] sqlParams)
        {
            using (SqlConnection conn = new SqlConnection(connStrs))
            {
                using (SqlCommand cmd = GetSqlCommand(sql, conn, cmdType, tran, sqlParams))
                {
                    try
                    {
                        conn.Open();
                        using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                        {
                            DataSet ds = new DataSet();
                            da.Fill(ds);
                            return ds;
                        }
                    }
                    catch (SqlException ex)
                    {
                        StringBuilder log = new StringBuilder();
                        log.Append("查詢數據錯誤：");
                        log.Append(ex);
                        throw new Exception(log.ToString());
                    }
                    finally
                    {
                        conn.Close();
                    }
                }
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="cmdType"></param>
        /// <param name="tran"></param>
        /// <param name="sqlParams"></param>
        /// <returns></returns>
        public static int ExecNonQuery(string sql, CommandType cmdType, SqlTransaction tran, params SqlParameter[] sqlParams)
        {
            /*定義： SqlCommand cmd = new SqlCommand()；//或者SqlCommand cmd = new SqlConnection().CreateCommand(); 註意參數
                cmd.CommandType = CommandType.StoredProcedure; //存儲過程
                cmd.CommandType = CommandType.Text; //sql語句
                cmd.CommandType = CommandType.TableDirect; System.Data.CommandType.TableDirect表示要執行的是表
                    ，此時，cmd.CommandText 的值應該是要查詢表的的名稱。查詢結果返回的是整個表。
             */
            int count = 0;
            using (SqlConnection conn = new SqlConnection(connStrs))
            {
                using (SqlCommand cmd = GetSqlCommand(sql, conn, cmdType, tran, sqlParams))
                {

                    try
                    {
                        conn.Open();

                        if (cmdType == CommandType.StoredProcedure)
                            cmd.Parameters.AddWithValue("@RETURN_VALUE", "").Direction = ParameterDirection.ReturnValue;
                        count = cmd.ExecuteNonQuery();
                        if (count <= 0)
                            if (cmdType == CommandType.StoredProcedure)
                                count = (int)cmd.Parameters["@RETURN_VALUE"].Value;
                    }
                    catch (SqlException ex)
                    {
                        StringBuilder log = new StringBuilder();
                        log.Append("查詢數據錯誤：");
                        log.Append(ex);
                        throw new Exception(log.ToString());
                    }
                    finally
                    {
                        conn.Close();
                    }
                }
            }
            return count;
        }
        public static object QueryScalar(string sql, CommandType cmdType, SqlTransaction tran, params SqlParameter[] sqlParams)
        {
            using (SqlConnection conn = new SqlConnection(connStrs))
            {
                using (SqlCommand cmd = GetSqlCommand(sql, conn, cmdType, tran, sqlParams))
                {
                    try
                    {
                        conn.Open();//創建cmd之前或之後Open都是可以的
                        return cmd.ExecuteScalar();
                    }
                    catch (SqlException ex)
                    {
                        StringBuilder log = new StringBuilder();
                        log.Append("查詢數據出錯：");
                        log.Append(ex);
                        throw new Exception(log.ToString());
                    }
                    finally
                    {
                        conn.Close();
                    }
                }
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="cmdType"></param>
        /// <param name="tran"></param>
        /// <param name="sqlParams"></param>
        /// <returns></returns>
        public static SqlDataReader GetDataReader(string sql, CommandType cmdType, SqlTransaction tran, params SqlParameter[] sqlParams)
        {
            //SqlDataReader要求，它讀取數據的時候有，它獨占它的SqlConnection對象，而且SqlConnection必須是Open狀態
            //SqlDataReader與SqlDataAdapter的區別：SqlDataReader為在線操作數據庫，SqlDataAdapter為離線操作（打開連接獲取數據集之後關閉連接，然後離線操作數據庫，然後再打開連接將數據更新到數據庫）
            using (SqlConnection conn = new SqlConnection(connStrs))
            {
                using (SqlCommand cmd = GetSqlCommand(sql, conn, cmdType, tran, sqlParams))
                {
                    try
                    {
                        conn.Open();
                        //CommandBehavior.CloseConnection當SqlDataReader釋放的時候，順便把SqlConnection對象也釋放掉
                        return cmd.ExecuteReader(CommandBehavior.CloseConnection);
                    }
                    catch (SqlException ex)
                    {
                        StringBuilder log = new StringBuilder();
                        log.Append("查詢數據錯誤：");
                        log.Append(ex);
                        throw new Exception(log.ToString());
                    }
                }
            }
        }
    }
}

C# sqlhelper 自練習