using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
 
namespace model 
{ 
  public class User 
  { 
    public User() { } 
    private string _name; 
    public string name 
    { 
      set { _name = value; } 
      get { return _name; } 
    } 
 
  } 
}

<add name="ConnectionString" connectionString="Data Source=localhost;Initial Catalog=tester;User ID=sa;Password=123456" providerName="System.Data.SqlClient" /> 

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using model; 
using System.Data; 
using System.Configuration; 
using System.Data.SqlClient; 
 
namespace DAL 
{ 
  public class UserDB 
  { 
    public bool User_add(model.User model) 
     { 
       string setting = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString(); 
       SqlConnection myconn=new SqlConnection(setting); 
       myconn.Open(); 
       SqlCommand cmd=new SqlCommand("insert into dbo.[user]([name]) values(@name)",myconn); 
       cmd.Parameters.AddWithValue("@name", model.name); 
       if (cmd.ExecuteNonQuery()>0) 
       { 
         return true; 
       } 
       else 
       { 
         return false; 
       } 
     } 
  } 
}

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using DAL; 
 
namespace BLL 
{   
     public class userBLL 
     { 
      DAL.UserDB db = new UserDB(); 
      public bool addUser(model.User model) 
       { 
        return db.User_add(model); 
       } 
     }   
}

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Windows.Forms; 
using BLL; 
using model; 
 
namespace 登陆 
{ 
  public partial class Form1 : Form 
  { 
    public Form1() 
    { 
      InitializeComponent(); 
    } 
 
    private void button1_Click(object sender, EventArgs e) 
    { 
      model.User thisUser = new User(); 
       thisUser.name = TB_username.Text.ToString(); 
       BLL.userBLL uB = new userBLL(); 
       if (uB.addUser (thisUser)) 
       { 
        MessageBox.Show ("true"); 
       } 
       else                           
       { 
         MessageBox.Show ("false"); 
       } 
     } 
    } 
  }