ADO.NET数据库简单操作

一、提交单条SQL语句

下面以一次数据库插入为例
1.定义连接字符串：Server=.;DataBase=StudentManageDB;Uid=sa;Pwd=admin，如果是连接非本机的数据库，在Server之后填写IP地址，Server服务器地址，DataBase数据库名，Uid用户名，Pwd密码
2.创建连接对象 SqlConnection conn = new SqlConnection(connString);
3.打开连接conn.Open();
4.编写sql
5.创建Command对象，并封装Connection和Sql语句SqlCommand cmd = new SqlCommand(sql, conn);创建Command对象的方法很多这里我们使用个人觉得比较简便的方法
6.执行操作ExecuteNonQuery方法int result = cmd.ExecuteNonQuery(); result的值为受影响的行数
7.关闭连接conn.Close();

namespace ADO.NETDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            //定义连接字符串
            string connString = "Server=.;DataBase=StudentManageDB;Uid=sa;Pwd=admin";
            //创建连接对象
            SqlConnection conn = new SqlConnection(connString);
            //打开连接
            conn.Open();
            if(ConnectionState.Open == conn.State)
            {
                Console.WriteLine("Connection is Opened");
            }

            //编写Sql
            string sql = "insert into Students(StudentName,Gender,Birthday,StudentIdNo,Age,PhoneNumber,StudentAddress,ClassId)";
            sql += "values('{0}','{1}','{2}',{3},{4},'{5}','{6}',{7})";
            sql = string.Format(sql, "呵呵", "男", "1990-09-12", 120225199609121213, 25, "15029635631", "天津", 1);
            //创建Command对象
            SqlCommand cmd = new SqlCommand(sql, conn);
            //执行操作
            int result = cmd.ExecuteNonQuery();
            conn.Close();
            if(ConnectionState.Closed == conn.State)
            {
                Console.WriteLine("Connection is Closed");
            }
            if(result == 1)
            {
                Console.WriteLine("添加成功");
            }
            else
            {
                Console.WriteLine("添加失败");
            }
            Console.ReadKey();
        }
    }
}

二、提交多条Sql语句
将多条sql语句中间通过分号连接“；”，例子如下

namespace ADO.NETDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            //定义连接字符串
            string connString = "Server=.;DataBase=StudentManageDB;Uid=sa;Pwd=admin";
            //创建连接对象
            SqlConnection conn = new SqlConnection(connString);
            //打开连接
            conn.Open();
            if(ConnectionState.Open == conn.State)
            {
                Console.WriteLine("Connection is Opened");
            }
            //编写Sql
            string sql = "insert into Students(StudentName,Gender,Birthday,StudentIdNo,Age,PhoneNumber,StudentAddress,ClassId)";
            sql += "values('{0}','{1}','{2}',{3},{4},'{5}','{6}',{7})";
            string sql1 = string.Format(sql, "呵呵1", "男", "1990-09-12", 120225199609101213, 25, "15029635631", "天津", 1);
            string sql2 = string.Format(sql, "呵呵2", "男", "1990-09-11", 120225199609111215, 25, "15029635651", "天津", 1);
            string sql3 = string.Format(sql, "呵呵3", "男", "1990-09-14", 120225199609121214, 25, "15029635631", "天津", 1);
            string Sql = sql1 + ";" + sql2 + ";" + sql3;
            //创建Command对象
            SqlCommand cmd = new SqlCommand(Sql, conn);
            //执行操作
            int result = cmd.ExecuteNonQuery();
            conn.Close();
            if(ConnectionState.Closed == conn.State)
            {
                Console.WriteLine("Connection is Closed");
            }
            if(result == 1)
            {
                Console.WriteLine("添加成功");
            }
            else
            {
                Console.WriteLine("添加失败");
            }
            Console.ReadKey();
        }
    }
}

这样通过分号连接后，我们通过断点调试可以看到当前的sql
这里写图片描述

三、获取标识列的值

在某些情景下我们可能需要拿到，新添加的记录的id，这时候我们可以使用@@identity获取。
1.首先在sql之后添加@@identity
2.使用ExecuteScalar()方法，这个方法可以同时执行insert和select object result = cmd.ExecuteScalar();ExecuteScalar方法的返回值是Object型
3.转换类型取得标识列的值Convert.ToInt32(result)
代码如下：

namespace ADO.NETDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            //定义连接字符串
            string connString = "Server=.;DataBase=StudentManageDB;Uid=sa;Pwd=admin";
            //创建连接对象
            SqlConnection conn = new SqlConnection(connString);
            //打开连接
            conn.Open();
            if(ConnectionState.Open == conn.State)
            {
                Console.WriteLine("Connection is Opened");
            }
            //编写Sql
            string sql = "insert into Students(StudentName,Gender,Birthday,StudentIdNo,Age,PhoneNumber,StudentAddress,ClassId)";
            sql += "values('{0}','{1}','{2}',{3},{4},'{5}','{6}',{7});Select @@identity";
            string sql1 = string.Format(sql, "呵呵00", "男", "1990-09-12", 120225099109101210, 25, "15029635631", "天津", 1);
            //创建Command对象
            SqlCommand cmd = new SqlCommand(sql1, conn);
            //执行操作
            object result = cmd.ExecuteScalar();
            conn.Close();
            if(ConnectionState.Closed == conn.State)
            {
                Console.WriteLine("Connection is Closed");
            }
            Console.WriteLine($"新添加的学员编号为{Convert.ToInt32(result)}");
            Console.ReadKey();
        }
    }
}

结果这里写图片描述

总结执行增删改的步骤

创建Connection对象
组合sql语句insert、update、delete
创建Command对象，并封装Connection和sql语句
打开连接
执行ExecuteNonQuery()方法，返回受影响的行数
关闭连接