使用ADO.NET

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！");             }

}

} }