C# Winform，先显示欢迎窗口，再显示登录窗口，最后显示主窗口

3个form:StartForm(主窗体),frmWelcome,frmLogin 

[STAThread] 
                 static    void    Main() 
                 { 
                         Application.EnableVisualStyles(); 
                         Application.SetCompatibleTextRenderingDefault(false); 
                         Application.Run(new    Form1()); 
                 } 

主窗口代码： 
   public    StartForm() 
                 { 
                         InitializeComponent(); 

                         //    显示欢迎窗口 
                         frmWelcome    frm1    =    new    frmWelcome(); 
                         if    (frm1.ShowDialog()    ==    DialogResult.OK) 
                         { 
                                 frmLogin    frm2    =    new    frmLogin(); 
                                 if    (frm2.ShowDialog()    !=    DialogResult.OK) 
                                 { 
                                         //      登入不成功 
                                         this.Close(); 
                                 } 
                         } 
                 } 

欢迎窗口代码（timer1是组件，控制5秒后关闭欢迎窗口）： 
         public    partial    class    frmWelcome    :    Form 
         { 
                 public    frmWelcome() 
                 { 
                         InitializeComponent(); 
                 } 

                 private    void    timer1_Tick(object    sender,    EventArgs    e) 
                 { 
                         this.DialogResult    =    DialogResult.OK; 
                         timer1.Enabled    =    false; 
                         timer1.Stop(); 
                         this.Close(); 
                 } 

                 private    void    frmWelcome_Load(object    sender,    EventArgs    e) 
                 { 
                         //      5秒后关闭欢迎窗口 
                         timer1.Interval    =    5000; 
                         timer1.Enabled    =    true; 
                         timer1.Start(); 
                 } 
         } 

登入窗口登入按钮代码： 
                 private    void    button1_Click(object    sender,    EventArgs    e) 
                 { 
                         //    登入成功，关闭登入窗口 
                         this.DialogResult    =    DialogResult.OK; 
                         this.Close(); 
                 }

把窗体顶部最小化最大化关闭菜单去掉：设置窗体的FormBorderStyle属性为None
让窗体居中：StartPosition属性为CenterScreen