namespaceBookManage{publicpartialclassfrmLogin:Form{publicfrmLogin(){InitializeComponent();}privatevoidbtnLogin_Click(objectsender,EventArgse){//验证通过if(Validate()){stringstate=this.cboUserType.Text;intnum;if(state.Equals("管理员"))//判断用户角色num=1;elseif(state.Equals("后台管理")){num=2;}else{num=3;}//定义查询语句stringsql=string.Format("select*fromuserinfowhereuname='{0}'andupwd='{1}'andustate={2}",this.txName.Text.Trim(),this.txtPwd.Text.Trim(),num);DataSetds=DataAccess.GetDataSetBySql(sql);if(ds.Tables[0].Rows.Count>0){MessageBox.Show("登录成功");Constans.UserBookID=ds.Tables[0].Rows[0]["UBookID"].ToString();Constans.UserName=ds.Tables[0].Rows[0]["UName"].ToString();Constans.UserState=ds.Tables[0].Rows[0]["UState"].ToString();if(num==1){frmMain.result=DialogResult.OK;this.Hide();frmMainmain=newfrmMain();main.ShowDialog();}elseif(num==2){frmBookInStorestore=newfrmBookInStore();store.ShowDialog();}else{frmBookJYjy=newfrmBookJY();jy.ShowDialog();}}elseMessageBox.Show("用户名或密码错误");}}privatevoidfrmLogin_Load(objectsender,EventArgse){this.cboUserType.SelectedIndex=0;}//验证方法privateboolVaildate(){if(this.txName.Text!=string.Empty&&this.txtPwd.Text!=string.Empty)returntrue;elseMessageBox.Show("用户名或密码不能为空");returnfalse;}privatevoidbtnCancle_Click(objectsender,EventArgse){this.Close();}}}namespaceBookManage{publicpartialclassfrmMain:Form{publicstaticDialogResultresult;publicfrmMain(){InitializeComponent();}//查询子窗体是否存在publicboolcheckchildfrm(stringchildfrmname){foreach(FormchildFrminthis.MdiChildren){if(childFrm.Name==childfrmname){if(childFrm.WindowState==FormWindowState.Minimized)childFrm.WindowState=FormWindowState.Normal;childFrm.Activate();returntrue;}}returnfalse;}//用户登录菜单的事件处理privatevoid用户登录ToolStripMenuItem_Click(objectsender,EventArgse){//检测该窗口是否处于打开状态if(this.checkchildfrm("frmLogin")==true)return;//窗口已经打开，返回frmLoginuser=newfrmLogin();//实例化登录窗体user.ShowDialog();//登录窗体