C#连接数据库-曾,删,改,查

连接数据库

        static void Main(string[] args)

        {

            //SqlConnection conn = new SqlConnection();//实例化

            //conn.ConnectionString = "server=.;database=mydb;uid=sa;pwd=123";//初始化-----可以用下面一条语句执行

            SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123");

            Console.WriteLine(conn.State);

            conn.Open();//打开数据库连接

            Console.WriteLine(conn.State);

            conn.Close();//关闭数据库连接

            Console.WriteLine(conn.State);

           

        }

连接数据库并插入数据

        static void Main(string[] args)

        {

            SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123");

            conn.Open();

            SqlCommand cmd = new SqlCommand();

            cmd.Connection = conn;//初始化,通过conn数据对象连接数据库

            cmd.CommandText = "insert into info values('p005','学生','0','n001','1990-02-1')";//""内为SQL语句

            cmd.ExecuteNonQuery();

            conn.Close();

            Console.WriteLine("OK");

        }

连接数据库并修改数据

        public static void Main(string[] args)

        {

            SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123");

            conn.Open();

            SqlCommand cmd = new SqlCommand();

            cmd.Connection = conn;

            cmd.CommandText = "update info set name='学员' where code='p005'";

            cmd.ExecuteNonQuery();

            conn.Close();

        }

连接数据库并删除数据

        public static void Main(string[] args)

        {

            SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123");                               

            conn.Open();            

            SqlCommand cmd = conn.CreateCommand();

            cmd.CommandText = "delete from info where code='p005'";

            cmd.ExecuteNonQuery();

            conn.Close();           

        }

 

 连接数据库查询数据

        static void Main(string[] args)

        {

            SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123");            

            conn.Open();

            SqlCommand cmd = conn.CreateCommand();

            cmd.CommandText = "select * from info";

            SqlDataReader r = cmd.ExecuteReader();//查询语句用ExecuteReader返回SqlDataReader类

            while (r.Read())

            {

                

                Console.WriteLine(r[0].ToString()+r[1].ToString()+r[2].ToString());

            }

            conn.Close();

        }

 

 

 案例:用户登录实现

        public static void Main(string[] arges)

        {

            Console.Write("用户名:");

            string uid = Console.ReadLine();

            Console.Write("密码:");

            string pwd = Console.ReadLine();

            SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123");            

            conn.Open();

            SqlCommand cmd = conn.CreateCommand();

            cmd.CommandText = "select * from login where username='"+uid+"' and password='"+pwd+"'";

            SqlDataReader r = cmd.ExecuteReader();

            if (r.HasRows == false)

            {

                Console.WriteLine("嗯哼,不对");

            }

            else

            {

                Console.WriteLine("嗯哼,正确");

            }

            conn.Close();

        }

*** .HasRows()与.read()区别:HasRows只关系读数据库中的数据是否可行,而不执行读的操作.Read是执行读的操作看是否执行成功.二者都返回一个bool行的变量.***