C# 封装sqlhelper 数据库

1.封装sqlhelper 可直接复制使用2

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;  //手动添加命名空间
using System.Data.SqlClient; //手动添加命名空间

namespace ConsoleApp1
{
    /// <summary>
    /// 查询
    /// </summary>
    class SqlHelper
    {
        private static string connstring= "Data Source =.; Initial Catalog = Students; Integrated Security = True";//连接数据库
        /// <summary>
        /// 返回单一结果查询
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static object GetSingleResult(string sql) //返回单一查询结果
        {
            SqlConnection connection = new SqlConnection(connstring); //创建数据库连接
            SqlCommand Cmd = new SqlCommand(sql, connection);
            connection.Open();//打开数据库连接
            object ob=Cmd.ExecuteScalar(); //返回查询结果
            connection.Close();//关闭连接
            return ob; 
        }
        /// <summary>
        /// 更新操作（insert updata，delete）
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static int Updata(string sql)
        {
            SqlConnection sqlConnection = new SqlConnection(connstring);
            SqlCommand sqlCommand = new SqlCommand(sql,sqlConnection);
            sqlConnection.Open();
            int i= sqlCommand.ExecuteNonQuery();
            sqlConnection.Close();
            return i;
        }
        /// <summary>
        /// 返回一个查询的结果集
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static SqlDataReader GetReader(string sql)
        {
            SqlConnection sqlConnection = new SqlConnection(connstring);
            SqlCommand sqlCommand = new SqlCommand(sql,sqlConnection);
            sqlConnection.Open();
            SqlDataReader sqlData= sqlCommand.ExecuteReader(CommandBehavior.CloseConnection); //该参数保证能够从外部关闭datareader时，与之关联的connection对象随之关闭
          //  sqlConnection.Close();//不能关闭数据库
            return sqlData;
        }
    }
}

2.调用

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

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            #region 调用SqlHelper.Updata方法
            string sql = "insert into Table_2(StudentName,Gender,Birthday,StudentIdNo," +
           "Age,PhoneNumber,StudentAddress,ClassId)" + "values('{0}','{1}','{2}','{3}','{4}'," +
           "'{5}','{6}','{7}')";
            sql = string.Format(sql, "王五", "男", "1994-03-13", "610481199811043056", 26, "15929533456",
                "北京市海淀区", 2);
            int i = SqlHelper.Updata(sql);
            Console.WriteLine(i);
            Console.ReadLine();
            #endregion

            #region 调用 SqlHelper.GetSingleResult方法，
            string sql = "select COUNT(*) from Table_2";
            object ob = SqlHelper.GetSingleResult(sql);
            Console.WriteLine(ob);
            Console.ReadLine();
            #endregion

            #region 调用 SqlHelper.GetReader返回多行数据
            string sql = "select StudentName from Table_2";
            SqlDataReader sqlData = SqlHelper.GetReader(sql);
            while (sqlData.Read())
            {
                Console.WriteLine(sqlData["StudentName"]);
            }
            sqlData.Close();//关闭读取器
            Console.ReadLine();
            #endregion

        }
    }
}