winform（三）——更换主窗体例子

namespace WindowsFormsApplication1
{
public partial class Login : Form
{
public string username;//定义一个变量给子窗体传值
public Login()
{
InitializeComponent();
} private void button1_Click(object sender, EventArgs e)
{
//取出用户名和密码
string uid = txtuid.Text;
string pwd = txtpwd.Text; if (uid != "" && pwd != "")
{
LoginDA da = new LoginDA(); //连接数据库
if (da.DengLu(uid, pwd)) //登录查询
{ //将用户名赋值给成员变量username
username = uid;
//将该窗体的返回值变为OK
this.DialogResult = DialogResult.OK;
//将该窗体关闭
this.Close(); }
else
{
MessageBox.Show("用户名或密码错误！");
}
}
else
{
MessageBox.Show("用户名和密码不能为空！");
}
} private void Login_Load(object sender, EventArgs e)
{ }
}
}

namespace WindowsFormsApplication1
{
static class Program
{
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false); //造一个登录窗体
Login log = new Login(); if (log.ShowDialog() == DialogResult.OK)
{
Application.Run(new Main(log.username));//main窗体的构造方法
}
}
}
}

namespace WindowsFormsApplication1
{
public partial class Main : Form
{
private string uid;//造一个变量接收Login窗体的值
private ChinaDA cda;
public Main()
{
InitializeComponent();
}
public Main(string username)
{
InitializeComponent();
uid = username; cda = new ChinaDA();//连接数据库
} private void Main_Load(object sender, EventArgs e)
{
label1.Text = uid;//把接收到的值传给label1显示一下 //填充省的下拉列表
FillSheng(); //填充市的下拉列表
FillShi(); //填充区的下拉列表
FillQu(); } private void cmbsheng_SelectedIndexChanged(object sender, EventArgs e)
{
//填充市的下拉列表
FillShi(); //填充区的下拉列表
FillQu();
} private void cmbshi_SelectedIndexChanged(object sender, EventArgs e)
{
//填充区的下拉列表
FillQu();
} //填充省的方法
public void FillSheng()
{
List<China> list = cda.Select(""); cmbsheng.DataSource = list;
cmbsheng.DisplayMember = "Name";
cmbsheng.ValueMember = "Code";
} //填充市的方法
public void FillShi()
{
List<China> list = cda.Select(cmbsheng.SelectedValue.ToString()); cmbshi.DataSource = list;
cmbshi.DisplayMember = "Name";
cmbshi.ValueMember = "Code";
} //填充区的方法
public void FillQu()
{
List<China> list = cda.Select(cmbshi.SelectedValue.ToString()); cmbqu.DataSource = list;
cmbqu.DisplayMember = "Name";
cmbqu.ValueMember = "Code";
} private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show(cmbsheng.SelectedValue.ToString());
}
}
}