C# sqlhelper 自练习

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//定义为abstract抽象类，不能被实例化，在应用时直接调用
    {
        /*1.获取数据库连接字符串；
         * 2.Connection 链接绑定，open/close；
         * 3.实例化一个Command命令，给定命令执行的超时时间 ，命令执行的连接；命令的类型（增/删/改/查）
         *      ，是否带事务，执行用到哪些参数，还有最重要的命令执行的sql字符串；
         * 4.SqlDataAdapter承接命令返回的结果集
         */
        private static int TimeOut = 5000;
        private static string connStrs = ConfigurationManager.ConnectionStrings["FirstBI.Properties.Settings.BaseERPConnectionString"].ConnectionString;
        /// <summary>
        /// 获取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("查询数据错误：");
                    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("查询数据错误：");
                        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)
        {
            /*定义： SqlCommand cmd = new SqlCommand()；//或者SqlCommand cmd = new SqlConnection().CreateCommand(); 注意参数
                cmd.CommandType = CommandType.StoredProcedure; //存储过程
                cmd.CommandType = CommandType.Text; //sql语句
                cmd.CommandType = CommandType.TableDirect; System.Data.CommandType.TableDirect表示要执行的是表
                    ，此时，cmd.CommandText 的值应该是要查询表的的名称。查询结果返回的是整个表。
             */
            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("查询数据错误：");
                        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();//创建cmd之前或之后Open都是可以的
                        return cmd.ExecuteScalar();
                    }
                    catch (SqlException ex)
                    {
                        StringBuilder log = new StringBuilder();
                        log.Append("查询数据出错：");
                        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，它读取数据的时候有，它独占它的SqlConnection对象，而且SqlConnection必须是Open状态
            //SqlDataReader与SqlDataAdapter的区别：SqlDataReader为在线操作数据库，SqlDataAdapter为离线操作（打开连接获取数据集之后关闭连接，然后离线操作数据库，然后再打开连接将数据更新到数据库）
            using (SqlConnection conn = new SqlConnection(connStrs))
            {
                using (SqlCommand cmd = GetSqlCommand(sql, conn, cmdType, tran, sqlParams))
                {
                    try
                    {
                        conn.Open();
                        //CommandBehavior.CloseConnection当SqlDataReader释放的时候，顺便把SqlConnection对象也释放掉
                        return cmd.ExecuteReader(CommandBehavior.CloseConnection);
                    }
                    catch (SqlException ex)
                    {
                        StringBuilder log = new StringBuilder();
                        log.Append("查询数据错误：");
                        log.Append(ex);
                        throw new Exception(log.ToString());
                    }
                }
            }
        }
    }
}