SQLHelper简单版(基础版)

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

namespace H.DAL
{
    /// <summary>
    /// 数据库操作帮助类
    /// 此段基础代码为SQLServer数据库帮助类
    ///     如需操作MySQL
    ///     1.将代码中Sql改为MySql
    ///     2.添加MySql.Data.dll引用(可通过官网或NuGet)
    ///     3.using System.Data.SqlClient;替换为using MySql.Data.MySqlClient;
    /// </summary>
    public class SQLHelper
    {
        /// <summary>
        /// 数据库连接字符串
        /// </summary>
        private static string connectionStr = 
　　　　　　　System.Configuration.ConfigurationManager.ConnectionStrings["dbConnection"].ConnectionString;
        public SQLHelper() { }
        public SQLHelper(string connectionStr)
        {
            SQLHelper.connectionStr = connectionStr;
        }
        /// <summary>
        /// 得到连接对象
        /// </summary>
        /// <returns></returns>
        public static SqlConnection GetConn()
        {
            SqlConnection sqlconn = null;
            sqlconn = new SqlConnection(connectionStr);
            return sqlconn;
        }

        /// <summary>
        /// 查询操作
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static DataTable GetDataTable(string sql, params SqlParameter[] sp)
        {
            using (SqlConnection conn = GetConn())
            {
                conn.Open();
                using (SqlDataAdapter sda = new SqlDataAdapter(sql, conn))
                {
                    sda.SelectCommand.Parameters.AddRange(sp);
                    DataTable dt = new DataTable();
                    sda.Fill(dt);
                    return dt;
                }
            }
        }
        /// <summary>
        /// 增删改操作
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <returns>执行后的条数</returns>
        public static int ExecuteNonQuery(string sql, params SqlParameter[] sp)
        {
            using (SqlConnection conn = GetConn())
            {
                conn.Open();
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddRange(sp);
                    int i = cmd.ExecuteNonQuery();
                    return i;
                }
            }

        }

        /// <summary>
        /// 执行一条SQL语句,返回首行首列
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <returns>首行首列</returns>
        public static object ExecuteScalar(string sql, params SqlParameter[] sp)
        {
            using (SqlConnection conn = GetConn())
            {
                conn.Open();
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddRange(sp);
                    return cmd.ExecuteScalar();
                }
            }
        }
    }
}

1.读取微软配置文件使用的System.Configuration.ConfigurationManager，需要添加引用

2.配置文件中需增加数据库连接节点，类似如下

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="dbConnection" connectionString="server=.;database=数据库名称;uid=用户名;pwd=密码;"/>
  </connectionStrings>
</configuration>