操作数据库（增删改）

删除

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

namespace ConsoleApplication1
{
class Program4
{
static void Main4(string[] args)
{
//用户输入要删除的数据主键值
Console.WriteLine("请输入要删除的代号：");
string code = Console.ReadLine();

//判断该数据存不存在
SqlConnection conn = new SqlConnection("server=.;database=mydb;user=sa;pwd=123");
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "select * from Info where Code='"+code+"'";
conn.Open();
SqlDataReader dr = cmd.ExecuteReader();

if (dr.HasRows)
{
//说明该数据存在
Console.WriteLine("查到该数据，是否要执行删除操作，如果要删除请输入：1");
int sc = Convert.ToInt32(Console.ReadLine());

if (sc == 1)
{
//删除
dr.Close(); //关闭读取器

cmd.CommandText = "delete from Info where Code='"+code+"'";
cmd.ExecuteNonQuery();
Console.WriteLine("删除成功！");

}
else
{
//不删除
dr.Read();

string sex = Convert.ToBoolean(dr[2])?"男":"女";
string nation = MinZu(dr[3].ToString());

string str = "代号："+dr[0]+" 姓名："+dr[1]+" 性别："+sex+" 民族："+nation+" 生日："+dr[4];

Console.WriteLine(str);

}
}
else
{
//数据不存在
Console.WriteLine("输入的代号错误！");
}

conn.Close();
Console.ReadLine();
}

static string MinZu(string code)
{
string name="";
SqlConnection conn = new SqlConnection("server=.;database=mydb;user=sa;pwd=123");
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "select Name from Nation where Code = '" + code + "'";
conn.Open();
SqlDataReader dr = cmd.ExecuteReader();
if (dr.HasRows)
{
dr.Read();
name = dr[0].ToString();
}
conn.Close();

return name;
}
}
}

添加

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

namespace ConsoleApplication1
{
class Program3
{
static void Main3(string[] args)
{
//让用户输入要添加的内容
Console.WriteLine("请输入要添加的代号：");
string code = Console.ReadLine();

Console.WriteLine("请输入姓名：");
string name = Console.ReadLine();

Console.WriteLine("请输入性别：");
bool sex = Console.ReadLine()=="男"?true:false;

Console.WriteLine("请输入民族：");
string nation = Console.ReadLine();

Console.WriteLine("请输入生日：");
string birthday = Console.ReadLine();

string nationcode = "n001";

//将民族名称转为名族代号
SqlConnection conn = new SqlConnection("server=.;database=mydb;user=sa;pwd=123");
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "select Code from Nation where Name = '"+nation+"'";
conn.Open();
SqlDataReader dr = cmd.ExecuteReader();
if (dr.HasRows)
{
dr.Read();
nationcode = dr[0].ToString();
}
conn.Close();

//往Info表添加数据
cmd.CommandText = "insert into Info values('"+code+"','"+name+"','"+sex+"','"+nationcode+"','"+birthday+"')";
conn.Open();
cmd.ExecuteNonQuery();
conn.Close();
Console.WriteLine("添加成功！");

Console.ReadLine();
}
}
}

修改

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

namespace ConsoleApplication1
{
class Program2
{
static void Main2(string[] args)
{
//造连接字符串
string connstring = "server=.;database=mydb;user=sa;pwd=123";

//造连接对象
SqlConnection conn = new SqlConnection(connstring);

//造命令对象
SqlCommand cmd = conn.CreateCommand();

//给SQL语句

cmd.CommandText = "update Info set Name='张三' where Code='p002'";

//打开连接
conn.Open();

//执行SQL语句
int n = cmd.ExecuteNonQuery();

if (n > 0)
{
Console.WriteLine("添加成功！");
}
else
{
Console.WriteLine("添加失败!");
}

//关闭连接
conn.Close();

Console.ReadLine();
}
}
}