查询单条数据

//数据库语句
select ClassId, ClassName from StudentClass where ClassId=1
//C# 数据库查询多条数据
           //定义SQL语句
            string sql = "select ClassId, ClassName from StudentClass where ClassId=1";
            //连接ADO.NET做数据查询
            SqlConnection conn = new SqlConnection(connString);//连接数据库(连接数据库实例)
            SqlCommand cmd = new SqlCommand(sql, conn); // 发送sql命令
            StudentClass student = new StudentClass();
            conn.Open(); //打开数据库连接
            //CommandBehavior.CloseConnection 检测并自动关闭数据库连接
            SqlDataReader reader =  cmd.ExecuteReader(CommandBehavior.CloseConnection);
            //解析数据
            if (reader.Read())
            {
                student = new StudentClass()
                {
                    ClassId = Convert.ToInt32(reader["ClassId"]),
                    ClassName = reader["ClassName"].ToString()
                };
            }
            //展示数据
            Console.WriteLine("班级Id" + student.ClassId + "\t" + "班级名称" + student.ClassName);

            Console.Read();
            

            //for(int j=0;j< result.l)


            List<test> list = new List<test>();
            List<int> i = new List<int>();

查询多条数据

//数据库语句
select ClassId, ClassName from StudentClass
//C# 数据库查询多条数据
        //定义SQL语句
        string sql = "select ClassId, ClassName from StudentClass";
        //连接ADO.NET做数据查询
        SqlConnection conn = new SqlConnection(connString);//连接数据库(连接数据库实例)
        SqlCommand cmd = new SqlCommand(sql, conn); // 发送sql命令
        List<StudentClass> sutlist = new List<StudentClass>();
        conn.Open(); //打开数据库连接
        //CommandBehavior.CloseConnection 检测并自动关闭数据库连接
        SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
        //解析数据
        while(reader.Read())
        {
            StudentClass student = new StudentClass()
            {
                ClassId = Convert.ToInt32(reader["ClassId"]),
                ClassName = reader["ClassName"].ToString()
            };
            sutlist.Add(student);
        }

        //展示数据
        foreach (var student in sutlist)
        {
            Console.WriteLine("班级Id" + student.ClassId + "\t" + "班级名称" + student.ClassName);
        };



        Console.Read();

//数据库语句
//字符串前加N 表示转义中文字符
insert into StudentClass (ClassId,ClassName) values(5,N'HTML5')
insert into StudentClass (ClassId,ClassName) values(6,N'Layui')
insert into StudentClass (ClassId,ClassName) values(7,N'C#进阶')
//c#操作数据插入
            string sql = "insert into StudentClass (ClassId,ClassName) values(8,N'python进阶')";
          //连接ADO.NET做数据查询
          SqlConnection conn = new SqlConnection(connString);//连接数据库(连接数据库实例)
          SqlCommand cmd = new SqlCommand(sql, conn); // 发送sql命令
          conn.Open(); //打开数据库连接
          int result = cmd.ExecuteNonQuery();
          Console.WriteLine("返回结果为: " + result);
          //解析数据

          Console.Read();

//数据库删除语句
//条件删除
delete from StudentClass where ClassId=8
//c#中条件删除数据库数据
//和增加相比只需要修改SQL语句
            //定义SQL语句
            string sql = "delete from StudentClass where ClassId=7";
            //连接ADO.NET做数据查询
            SqlConnection conn = new SqlConnection(connString);//连接数据库(连接数据库实例)
            SqlCommand cmd = new SqlCommand(sql, conn); // 发送sql命令
            conn.Open(); //打开数据库连接
            int result = cmd.ExecuteNonQuery();
            Console.WriteLine("返回结果为: " + result);
            //解析数据

            Console.Read();

//数据库修改数据语句
//条件修改
update StudentClass set ClassName=N'Layui基础' where ClassId=6
//c#中条件修改数据库数据
//和增加相比只需要修改SQL语句
            //定义SQL语句
            string sql = "update StudentClass set ClassName=N'Layui进阶' where ClassId=6";
            //连接ADO.NET做数据查询
            SqlConnection conn = new SqlConnection(connString);//连接数据库(连接数据库实例)
            SqlCommand cmd = new SqlCommand(sql, conn); // 发送sql命令
            conn.Open(); //打开数据库连接
            int result = cmd.ExecuteNonQuery();
            Console.WriteLine("返回结果为: " + result);
            //解析数据

            Console.Read();