C#SQLServer数据库通用访问类

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

namespace thinger.cn.ADO.NETTeach
{
///
/// 数据库的通用类
///
public class SQLHelperBase
{
//定义连接字符串
private static string connString = “Server=.;DataBase=MISDB;Uid=sa;Pwd=123456”;

    /// <summary>
    /// 执行增删改操作
    /// </summary>
    /// <param name="cmdText">SQL语句</param>
    /// <returns></returns>
    public static int ExecuteNonQuery(string cmdText)
    {
        //【1】创建连接对象
        SqlConnection conn = new SqlConnection(connString);          
        //【2】创建Command对象
        SqlCommand cmd = new SqlCommand(cmdText, conn);
        try
        {
            //【3】打开连接
            conn.Open();
            //【4】执行操作
            return cmd.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            //根据需要把异常信息写到日志中...

            throw new Exception($"执行方法ExecuteNonQuery()发生异常：{ex.Message}");
        }
        finally
        {
            //【5】关闭连接
            conn.Close();
        }           
    }
    /// <summary>
    /// 执行返回单行单列的结果查询
    /// </summary>
    /// <param name="cmdText"></param>
    /// <returns></returns>
    public static object ExecuteScalar(string cmdText)
    {          
        SqlConnection conn = new SqlConnection(connString);         
        SqlCommand cmd = new SqlCommand(cmdText, conn);
        try
        {              
            conn.Open();             
            return cmd.ExecuteScalar();
        }
        catch (Exception ex)
        {
            //根据需要把异常信息写到日志中...

            throw new Exception($"ExecuteScalar()发生异常：{ex.Message}");
        }
        finally
        {             
            conn.Close();
        }
    }
    /// <summary>
    /// 执行返回一个多行多列结果集的查询
    /// </summary>
    /// <param name="cmdText"></param>
    /// <returns></returns>
    public static SqlDataReader ExecuteReader(string cmdText)
    {
        SqlConnection conn = new SqlConnection(connString);
        SqlCommand cmd = new SqlCommand(cmdText, conn);
        try
        {
            conn.Open();
            return cmd.ExecuteReader(CommandBehavior.CloseConnection);
        }
        catch (Exception ex)
        {
            //根据需要把异常信息写到日志中...

            throw new Exception($"ExecuteReader()发生异常：{ex.Message}");
        }
        //finally  //这个地方是不能关闭的
        //{
        //    conn.Close();
        //}
    }
}

}