SQLHelper类

　简单的SQLHelper类

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

namespace MyDBHelper
{
    public class SQLHelper
    {
        //获取连接字符串，从配置文件中 
        //不加密
        private readonly string strConn = ConfigurationManager.ConnectionStrings["strConn"].ConnectionString;

        //执行非查询语句 返回受影响的行数
        public static int ExecuteNonQuery(string commandText,params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(strConn))
            {
                using (SqlCommand cmd = new SqlCommand(commandText,conn))
                {
                    cmd.CommandType = CommandType.Text;//默认是CommandType.Text
                    if (parameters.Length > 0)
                    {
                        cmd.Parameters.AddRange(parameters);
                    }
                    conn.Open();
                    return cmd.ExecuteNonQuery();
                }
            }
        }
        /// <summary>
        /// 查询符合SQL语句的数据，填充数据表中
        /// </summary>
        /// <param name="commandText">实质是sql语句</param>
        /// <param name="parameters">sql语句中的参数</param>
        /// <returns></returns>
        public static DataTable ExecuteDataTable(string commandText,params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(strConn))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())//可以通过conn创建SqlCommand对象，也可以直接new
                {
                    cmd.CommandText = commandText;
                    cmd.CommandType = CommandType.Text;
                    cmd.Parameters.AddRange(parameters);
                    DataSet ds = new DataSet();
                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                    adapter.Fill(ds);
                    return ds.Tables[0];
                }
            }
        }
        /// <summary>
        /// 执行SQL语句查询 返回结果集中的第一行第一列的值
        /// </summary>
        /// <param name="commandText">SQL语句</param>
        /// <param name="parameters">参数。可变参数</param>
        /// <returns></returns>
        public static object ExecuteScalar(string commandText,params SqlParameter[] parameters)
        {
            using(SqlConnection conn=new SqlConnection(strConn))
            {
                conn.Open();
                using(SqlCommand cmd=conn.CreateCommand())
                {
                    cmd.CommandText=commandText;
                    cmd.CommandType=CommandType.Text;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteScalar();
                }
            }
        }
    }
}