用户登录模块问题！！从前台界面输入用户名和密码如何与后台定义的类做比较，并成功验证登录进入系统！！

以下是我做的三层架构：
实体类：
using System;
using System.Collections.Generic;
using System.Text;


namespace BYJ.Entity
{
[Serializable]
public class UserInfo
{
private char zgxm;
private string zgbh;
private string bmbh;
private string bmmc;
private string password;


public char Zgxm
{
get { return this.zgxm; }
set { this.zgxm = value; }
}
public string Zgbh
{
get { return this.zgbh; }
set { this.zgbh = value; }
}
public string Bmbh
{
get { return this.bmbh; }
set { this.bmbh = value; }
}
public string Bmmc
{
get { return this.bmmc; }
set { this.bmmc = value; }
}
public string Password
{
get { return this.password; }
set { this.password = value; }
}
}
}


业务逻辑层接口：
using System;
using System.Collections.Generic;
using System.Text;
using BYJ.Entity;

namespace BYJ.IBLL
{
public interface IUserBll
{
/**/
/// <summary>
/// 职工登录
/// </summary>
/// <param name="zgxm">职工登录名</param>
/// <param name="password">职工密码</param>
/// /// <returns>如果登录成功，则返回true，否则返回false</returns>
bool Login(string zgxm, string password);
/**/
/// <summary>
/// 取得全部职工信息
/// </summary>
/// <returns>职工实体类集合</returns>
IList<UserInfo> GetAll();
/// <summary>
/// 通过职工姓名取得职工信息
/// </summary>
/// <param name="zgbh"></param>
/// <returns></returns>
UserInfo GetByName(string zgxm);
/**/
/// <summary>
/// 通过职工权限返回职工操作的权限功能
/// </summary>
/// <param name="zgbh">职工编号</param>
/// <param name="zgqx">职工权限</param>
/// <returns>如果返回权限值为1，为普通用户，返回值为2，则是管理员用户</returns>
bool yhxx(string zgbh, string zgqx);
}
}

数据访问层接口
using System;
using System.Collections.Generic;
using System.Text;
using BYJ.Entity;

namespace BYJ.IDAL
{
public interface IUserDAL
{
///<summary>
///返回所有职工信息
///</summary>
///<returns></returns>
IList<UserInfo> GetAll();
/**/
/// <summary>
/// 会员登录
/// </summary>
/// <param name="name">会员登录名</param>
/// <param name="password">会员密码</param
/// /// <returns>如果登录成功，则返回true，否则返回false</returns>
bool Login(string zgxm, string password);
/// <summary>
/// 是否是本站的用户
/// </summary>
/// <param name="name"></param>
/// <param name="pwd"></param>
/// <returns></returns>
bool IsRight(string zgxm, string password);
///<summary>
///通过职工姓名返回职工信息
///</summary>
///<param name="zgxm"></param>
///<returns></returns>
UserInfo GetByName(string zgxm);
}
}


数据访问层：
using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using BYJ.IDAL;
using BYJ.Entity;


namespace BYJ.SQLServerDAL
{
public class UserDAL:IUserDAL
{
public bool IsRight(String zgxm, string password)

{
string sql = "select '" + zgxm + "','"+password+"' from yhxx ";


try
{
SQLServerDALHelper.ExecuteSQLReader(sql);
return true;
}
catch
{
return false;
}

}
}



业务逻辑层：

using System;
using System.Collections.Generic;
using System.Text;
using BYJ.Entity;
using BYJ.IBLL;
using BYJ.IDAL;
using BYJ.SQLServerDAL;

namespace BYJ.BLL
{
public class UserBLL : IUserBll
{
public bool ChangePassword(string zgxm, string password)
{
return ChangePassword(zgxm, password);
}
/**/
/// <summary>
/// 会员登录
/// </summary>
/// <param name="zgxm">会员登录名</param>
/// <param name="password">会员密码</param>
/// <returns>如果登录成功，则返回true 否则返回false</returns>
public bool Login(string zgxm, string password)
{
return Login (zgxm, password);
}

private bool IsRight(string zgxm, string password)
{
return IsRight(zgxm, password);
}

/**/
/// <summary>
/// 取得全部会员信息
/// </summary>
/// <returns>会员实体类集合</returns>
public IList<UserInfo> GetAll()
{
UserDAL user = new UserDAL();
IList<UserInfo> userCollection = new List<UserInfo>();
userCollection=user.GetAll();
return userCollection;

}
/// <summary>
/// 通过会员名返回会员信息
/// </summary>
/// <param name="username"></param>
/// <returns></returns>
public UserInfo GetByName(string zgxm)
{
return GetByName(zgxm);
}
}
}

表示层，登陆页面：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using BYJ.BLL;
using BYJ.Entity;
using BYJ.IBLL;
using BYJ.IDAL;
using BYJ.SQLServerDAL;


public partial class Login : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

}
/// <summary>
/// 提交登录信息
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>

protected void Button1_Click(object sender, EventArgs e)
{
string zgxm = this.TextBox1.Text.ToString();
string password = this.TextBox2.Text.ToString();
//如果信息符合把登录名赋给Session
if (UserBLL.IsRight(zgxm , password ))
{
Session.Add("zgxm", zgxm );
Response.Redirect("Default.aspx");
}
else
{
Response.Redirect("登录失败");
}
}








/// <summary>
/// 清空登录信息
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Button2_Click(object sender, EventArgs e)
{
this.TextBox1.Text = "";
this.TextBox2.Text = "";
}
protected void TextBox1_TextChanged(object sender, EventArgs e)
{

}
}



求高人解答，怎样才能进入系统并成功跳转到Default页面!