sql增删改查封装

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
<connectionStrings>
<add connectionString="Data Source = .; Initial Catalog = mysql; Integrated Security = True;" name="conStr" />
</connectionStrings>
</configuration>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
//新建一个App.confit文件，引用下面两个命名空间
using System.Configuration;
using System.Data.SqlClient;

namespace 封装
{
public class SqlHelper
{
//读取连接字符串
private static readonly string str = ConfigurationManager.ConnectionStrings["conStr"].ConnectionString;
//三个方法，关键是第三个方法，查询，条件判断比较多
/// <summary>
/// 此方法可以做增删改
/// </summary>
/// <param name="sql">sql语句</param>
/// <param name="ps">sql语句中的参数</param>
/// <returns>返回受影响的行数，int类型</returns>
private static int ExecuteNonQuery(string sql, params SqlParameter[] ps)
{
using (SqlConnection con = new SqlConnection(str))
{
using (SqlCommand cmd = new SqlCommand(sql, con))
{
con.Open();
if (ps != null)
{
cmd.Parameters.AddRange(ps);
}

return cmd.ExecuteNonQuery();
}
}
}
/// <summary>
/// 该方法用在查询上
/// </summary>
/// <param name="sql">sql语句</param>
/// <param name="ps">sql语句中的参数</param>
/// <returns>返回首行首列，object类型</returns>
private static object ExecuteScalar(string sql, params SqlParameter[] ps)
{
using (SqlConnection con = new SqlConnection(str))
{
using (SqlCommand cmd = new SqlCommand(sql, con))
{
con.Open();
if (ps != null)
{
cmd.Parameters.AddRange(ps);
}
return cmd.ExecuteScalar();
}
}
}
/// <summary>
/// 该方法用于查询，读数据
/// </summary>
/// <param name="sql">sql语句</param>
/// <param name="ps">sql语句中的参数</param>
/// <returns>返回sqldatareader对象，里面有数据</returns>
private static SqlDataReader ExecuteReader(string sql, params SqlParameter[] ps)
{
//这地方不用using，因为不知道什么时候释放
SqlConnection con = new SqlConnection(str);
using (SqlCommand cmd = new SqlCommand(sql,con))
{
if (ps!=null)
{
cmd.Parameters.AddRange(ps);
}
try
{
con.Open();
//这个重载会datareader关闭时，自动关闭connection
return cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
}
catch (Exception ex)
{
con.Close();
con.Dispose();
throw ex;
}
}
}
}
}