简单的登陆页面

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 人事考勤系统;
using System.Collections;
using AnbySQL;

namespace 人事考勤系统
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private string logintype = "";
public string Logintype
{
get { return combRole.Text; }
}
public string LoginID
{
get { return txtUserid.Text.Trim(); }
}

private void Form1_Load(object sender, EventArgs e)
{
DataTable dt = new DataTable();
List<string> role=new List<string>();
string sql = "select * from UserInfo";
dt= AnbySQL.DbHelperSQL.DataQuery(sql).Tables[0];
for(int i=0;i<dt.Rows.Count;i++)
{
role.Add(dt.Rows[i]["username"].ToString());
}
combRole.DataSource = role;
}

private void btnLogin_Click(object sender, EventArgs e)
{
ChkContol();
logintype = combRole.Text;
DataTable dt =GoLogin();

if (dt.Rows.Count > 0)
{
this.DialogResult= DialogResult.OK;
}
else
MessageBox.Show("登录失败");
}

private DataTable GoLogin()
{
DataTable dt = new DataTable();
string sql = "select count(*) from userinfo where username='" + txtUserid.Text.Trim() + "' and Password='" + txtPwd.Text.Trim() + "'";
return dt = AnbySQL.DbHelperSQL.DataQuery(sql).Tables[0];
}

private void btnCancel_Click(object sender, EventArgs e)
{
Application.Exit();
}

public void ChkContol()
{
if (txtUserid.Text == "" || txtPwd.Text == "" || combRole.Text == "")
{
MessageBox.Show("用户名,密码，角色不能为空");
}

}
}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace 人事考勤系统
{
static class Program
{
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);

Form1 frmLogin = new Form1();
Form frmMain = null;
if (frmLogin.ShowDialog() == DialogResult.OK)
{
frmMain = new 主界面();
UserHelper.LoginID = frmLogin.LoginID;
UserHelper.LoginType = frmLogin.Logintype;
}
Application.Run(frmMain);


}
}
}