Program

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Data.SqlClient;

namespace 打开数据库

{

class Program

{

static void Main(string[] args)

{

#region 连接数据库

//步骤一：配置参数（连接到服务器，连接的数据库名称，用户名，密码）

string str = "Data Source=.;Initial Catalog=Myschool;User ID=sa;pwd=1";

//步骤二：创建Connection对象连接数据库（SqlConnection）

SqlConnection con = new SqlConnection(str);

//步骤三：打开数据库

con.Open();

Console.WriteLine("打开数据库成功！");

//步骤N：将数据库关闭

con.Close();

Console.WriteLine("关闭数据库成功！");

#endregion

#region 数据库异常

try

{

con.Open();

}

catch(SqlException ex){

Console.WriteLine("出现异常"+ex); 

}

catch (Exception ex)

{

Console.WriteLine("出现异常！" + ex);

}

finally {

con.Close();

Console.WriteLine("关闭数据库成功！");

}

#endregion

#region 登录

Console.WriteLine("请输入用户名：");

string loginID = Console.ReadLine();

Console.WriteLine("请输入密码：");

string loginPwd = Console.ReadLine();

User user = new User();

user.login(loginID, loginPwd);

#endregion

Console.ReadLine();

}

}

}

 

ConnectionDB类

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Data.SqlClient;

namespace 打开数据库

{

class ConnectionDB

{

static string str = "Data Source=.;Initial Catalog=Myschool;User ID=sa;password=1";

public SqlConnection con = new SqlConnection(str);

public void OpenDB() 

{

try

{

con.Open();

}

catch (Exception ex)

{

Console.WriteLine("发生异常！"+ex);

}

}

public void CloseDB() 

{

con.Close();

}

}

}

 

User类

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Data.SqlClient;

namespace 打开数据库

{

class User

{

ConnectionDB bd = new ConnectionDB();

public void login(string StudentNo, string loingPwd)

{

string sql = "SELECT COUNT(1) FROM Student WHERE StudentNo='" + StudentNo + "' AND Loginpwd='" + loingPwd + "'";

Console.WriteLine(sql);

bd.OpenDB();

SqlCommand cmd = new SqlCommand(sql, bd.con);

int count = (int)cmd.ExecuteScalar();

if (count > 0)

{

Console.WriteLine("登录成功！");

}

else

{

Console.WriteLine("登录失败！");

}

}

}

}