sql增删改查封装

App.config文件

 <?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>

sqlHelper封装类库代码

 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;
                 }
             }
         }
     }
 }