C#连接数据库

VScode 配置C#环境 https://blog.csdn.net/qq_40346899/article/details/80955788

VScode 配置C#开发环境

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

using System.Data;
using System.Data.SqlClient;

namespace ADODome
{
    class Program
    {
        static void Main(string[] args)
        {
                     
            string connString_1 = @"server=.SQLEXPRESS;uid=sa;pwd=123456;database=Stu";
            SqlConnection conn = new SqlConnection(connString_1);
            conn.Open();
            if (ConnectionState.Open == conn.State)
            {
                Console.WriteLine("Connection is Opend!");
            }
            conn.Close();
            if(ConnectionState.Closed == conn.State)
            {
                Console.WriteLine("Connection is close!");
            }
        }
    }
}

封装类

class SqlHelp
    {
        private static string str = @"server=.SQLEXPRESS;uid=sa;pwd=123456;database=Stu";

        public static object GetSingleResult(String sql)
        {
            SqlConnection conn = new SqlConnection(str);
            SqlCommand cmd = new SqlCommand(sql, conn);
            conn.Open();
            object result = cmd.ExecuteScalar();
            conn.Close();
            return result;
        }

        public static int Update(String sql)
        {
            SqlConnection conn = new SqlConnection(str);
            SqlCommand cmd = new SqlCommand(sql, conn);
            conn.Open();
            int result = cmd.ExecuteNonQuery();
            conn.Close();
            return result;
        }

        public static SqlDataReader GetReader(String sql)
        {
            SqlConnection conn = new SqlConnection(str);
            SqlCommand cmd = new SqlCommand(sql, conn);
            conn.Open();
            //CommandBehavior.CloseConnection
            //不使用conn.close()
            SqlDataReader result = cmd.ExecuteReader(CommandBehavior.CloseConnection);           
            return result;
        }
    }

调用封装类 

 public int AddStudent( string name)
        {
            //"insert into student values('{0}');select @@identity";
            string sql = "insert into student values('{0}');select @@identity";
            sql = string.Format(sql, name);
            return SqlHelp.Update(sql);

        }

        public void GetStu(int age)
        {
            string sql = "select * from student where age="+age;
            SqlDataReader reader =  SqlHelp.GetReader(sql);
            while (reader.Read())
            {
                Console.WriteLine("age:"+reader["age"] +";	name:"+reader["name"]);
            }
            reader.Close();

        }