獲取工具下載 - DevExpress v21.2

從本文檔中，您將了解如何向應用程序添加登錄表單。在本節(jié)教程中著重討論了如何實現(xiàn)此任務，這基本上是附加應用程序功能的一部分。

4. 您還需要向主表單的ViewModel中添加一些代碼。由于主表單使用自動生成的MyDbContextViewModel 類，因此不建議將自定義代碼直接添加到其中 - 如果您需要再次調(diào)用Scaffolding Wizard，可以重新生成模型。相反，創(chuàng)建一個位于單獨文件中的部分類。 請注意，您必須將類構造函數(shù)從其原始文件移動到這個分部類。

C#

//MyDbContextViewModel.partial.cs
public partial class MyDbContextViewModel {
LoginViewModel loginViewModel;

protected MyDbContextViewModel()
: base(UnitOfWorkSource.GetUnitOfWorkFactory()) {
loginViewModel = LoginViewModel.Create();
loginViewModel.SetParentViewModel(this);
}
protected IDialogService DialogService {
get { return this.GetService<IDialogService>(); }
}
protected IMessageBoxService MessageService {
get { return this.GetService<IMessageBoxService>(); }
}

public override void OnLoaded(MyDbContextModuleDescription module) {
base.OnLoaded(module);
Login();
}

public virtual AppState State { get; set; }
// Shows the Login View
public void Login() {
OnLogin(DialogService.ShowDialog(MessageButton.OKCancel, "Please enter you credentials", "LoginView", loginViewModel));
}
//Occurs whenever the end-user clicks a dialog button
void OnLogin(MessageResult result) {
if(result == MessageResult.Cancel)
State = AppState.ExitQueued;
else {
if(loginViewModel.IsCurrentUserCredentialsValid)
State = AppState.Autorized;
else
Login();
}
}
protected void OnStateChanged() {
this.RaiseCanExecuteChanged(x => x.Logout());
if(State == AppState.Autorized)
Messenger.Default.Send<string>(loginViewModel.CurrentUser.Login);
else
Messenger.Default.Send<string>(string.Empty);
}
}

public enum AppState {
NotAutorized,
Autorized,
ExitQueued
}

VB.NET

'MyDbContextViewModel.partial.vb
Partial Public Class MyDbContextViewModel
Private loginViewModel As LoginViewModel

Protected Sub New()
MyBase.New(UnitOfWorkSource.GetUnitOfWorkFactory())
loginViewModel = LoginViewModel.Create()
loginViewModel.SetParentViewModel(Me)
End Sub
Protected ReadOnly Property DialogService() As IDialogService
Get
Return Me.GetService(Of IDialogService)()
End Get
End Property
Protected ReadOnly Property MessageService() As IMessageBoxService
Get
Return Me.GetService(Of IMessageBoxService)()
End Get
End Property

Public Overrides Sub OnLoaded(ByVal [module] As MyDbContextModuleDescription)
MyBase.OnLoaded([module])
Login()
End Sub

Public Overridable Property State() As AppState
' Shows the Login View
Public Sub Login()
OnLogin(DialogService.ShowDialog(MessageButton.OKCancel, "Please enter you credentials", "LoginView", loginViewModel))
End Sub
'Occurs whenever the end-user clicks a dialog button
Private Sub OnLogin(ByVal result As MessageResult)
If result Is MessageResult.Cancel Then
State = AppState.ExitQueued
Else
If loginViewModel.IsCurrentUserCredentialsValid Then
State = AppState.Autorized
Else
Login()
End If
End If
End Sub
Protected Sub OnStateChanged()
Me.RaiseCanExecuteChanged(Sub(x) x.Logout())
If State = AppState.Autorized Then
Messenger.Default.Send(Of String)(loginViewModel.CurrentUser.Login)
Else
Messenger.Default.Send(Of String)(String.Empty)
End If
End Sub
End Class

Public Enum AppState
NotAutorized
Autorized
ExitQueued
End Enum

下面列出了 LoginViewModel 和兩個視圖（MainView 和 LoginView）的代碼。 當您的 ViewModel 準備就緒時，重新構建項目并將 MvvmContext 組件添加到登錄表單中，使用其智能標簽將 LoginViewModel 分配為此視圖的相關視圖模型。

C#

//LoginViewModel.cs
public class LoginViewModel {
public IEnumerable<string> LookUpUsers {
get { return CredentialsSource.GetUserNames(); }
}
public virtual User CurrentUser { get; set; }
public bool IsCurrentUserCredentialsValid { get; private set; }

[DevExpress.Mvvm.DataAnnotations.Command(false)]
public void Init() {
this.CurrentUser = new User();
}
public void Update() {
IsCurrentUserCredentialsValid = CredentialsSource.Check(CurrentUser.Login, CurrentUser.Password);
}
public static LoginViewModel Create() {
return ViewModelSource.Create<LoginViewModel>();
}
}

//MainView.cs
public MainView() {
InitializeComponent();
this.Opacity = 0;
. . .
}

void InitializeNavigation() {
. . .
var fluentAPI = mvvmContext1.OfType<MyDbContextViewModel>();
fluentAPI.SetTrigger(x => x.State, (state) =>
{
if(state == AppState.Autorized)
Opacity = 1; /*Show Main Form*/
if(state == AppState.ExitQueued)
Close(); // exit the app;
});
}

//LoginView.cs
public partial class LoginView : DevExpress.XtraEditors.XtraUserControl {
public LoginView() {
InitializeComponent();
}

protected override void OnLoad(System.EventArgs e) {
base.OnLoad(e);
var fluentAPI = mvvmContext1.OfType<LoginViewModel>();
fluentAPI.SetObjectDataSourceBinding(userBindingSource,
x => x.CurrentUser, x => x.Update());

foreach(string item in mvvmContext1.GetViewModel<LoginViewModel>().LookUpUsers)
LoginTextEdit.Properties.Items.Add(item);
fluentAPI.ViewModel.Init();
}
}

VB.NET

'LoginViewModel.vb
Public Class LoginViewModel
Public ReadOnly Property LookUpUsers() As IEnumerable(Of String)
Get
Return CredentialsSource.GetUserNames()
End Get
End Property
Public Overridable Property CurrentUser() As User
Private privateIsCurrentUserCredentialsValid As Boolean
Public Property IsCurrentUserCredentialsValid() As Boolean
Get
Return privateIsCurrentUserCredentialsValid
End Get
Private Set(ByVal value As Boolean)
privateIsCurrentUserCredentialsValid = value
End Set
End Property

<DevExpress.Mvvm.DataAnnotations.Command(False)>
Public Sub Init()
Me.CurrentUser = New User()
End Sub
Public Sub Update()
IsCurrentUserCredentialsValid = CredentialsSource.Check(CurrentUser.Login, CurrentUser.Password)
End Sub
Public Shared Function Create() As LoginViewModel
Return ViewModelSource.Create(Of LoginViewModel)()
End Function
End Class

'MainView.vb
Public Sub New()
InitializeComponent()
Me.Opacity = 0
. . .
End Sub

Private Sub InitializeNavigation()
. . .
Dim fluentAPI = mvvmContext1.OfType(Of MyDbContextViewModel)()
fluentAPI.SetTrigger(Function(x) x.State, Sub(state)
If state = AppState.Autorized Then
Opacity = 1
End If
If state = AppState.ExitQueued Then
Close()
End If
End Sub) ' exit the app; - Show Main Form
End Sub

'LoginView.vb
Partial Public Class LoginView
Inherits DevExpress.XtraEditors.XtraUserControl

Public Sub New()
InitializeComponent()
End Sub

Protected Overrides Sub OnLoad(ByVal e As System.EventArgs)
MyBase.OnLoad(e)
Dim fluentAPI = mvvmContext1.OfType(Of LoginViewModel)()
fluentAPI.SetObjectDataSourceBinding(userBindingSource, Function(x) x.CurrentUser, Function(x) x.Update())

For Each item As String In mvvmContext1.GetViewModel(Of LoginViewModel)().LookUpUsers
LoginTextEdit.Properties.Items.Add(item)
Next item
fluentAPI.ViewModel.Init()
End Sub
End Class

此代碼使用 OnLoaded 方法重載來顯示使用已注冊 DialogService 的對話框，為此Login方法調(diào)用服務的ShowDialog擴展方法，此方法將子 ViewModel 作為參數(shù) - 將 LoginViewModel 類的新實例傳遞給它。創(chuàng)建這個實例很重要，不是使用 new 關鍵字，而是調(diào)用 ViewModelSource.Create<ViewModelType> 方法。或者，您可以調(diào)用 SetParentViewModel 方法為此實例設置父 ViewModel。

當最終用戶單擊任何登錄對話框的按鈕時，此消息結果將傳遞給 OnLogin 方法，該方法會準確檢查單擊了哪個按鈕。 如果最終用戶單擊 ‘Cancel’ 或關閉對話框，則應用程序?qū)㈥P閉。如果單擊‘OK’按鈕，應用程序?qū)z查 IsCurrentUserCredentialsValid 屬性，該屬性會在調(diào)用 Update 方法時自動刷新其值。如果輸入的憑據(jù)有效，將顯示主表單，否則將重新顯示登錄表單，這是通過為 State 屬性分配不同的值來完成的。 MainView 有一個觸發(fā)器，用于監(jiān)視 State 屬性值的變化，并在它發(fā)生時做出相應的反應。

5. 前面的步驟足以實現(xiàn)具有最少功能的登錄表單。 但是，如果您的主視圖分配了關閉確認操作，可能會遇到某些問題。 例如，如果您關閉登錄表單，主表單（由于未輸入有效憑據(jù)而變得透明）也將嘗試自行關閉。 這將顯示確認消息，如果您單擊‘Cancel’按鈕，表格將保留，但您將看不到它。 要克服此類問題，請刪除表單關閉操作（如果有）并添加以下代碼。

C#

//MainView.cs
fluentAPI.WithEvent<FormClosingEventArgs>(this, "FormClosing")
.EventToCommand(x => x.OnClosing(null), new Func<CancelEventArgs, object>((args) => args));

//MyDbContextViewModel.partial.cs
public override void OnClosing(CancelEventArgs cancelEventArgs) {
base.OnClosing(cancelEventArgs);
if(!cancelEventArgs.Cancel) {
if(State == AppState.Autorized && MessageService.ShowMessage("Do you really want to close the application?", "Confirm", MessageButton.YesNo) == MessageResult.No)
cancelEventArgs.Cancel = true;
}
}

VB.NET

'MainView.vb
fluentAPI.WithEvent(Of FormClosingEventArgs)(Me, "FormClosing").EventToCommand(Function(x) x.OnClosing(Nothing), New Func(Of CancelEventArgs, Object)(Function(args) args))

'MyDbContextViewModel.partial.vb
public override void OnClosing(CancelEventArgs cancelEventArgs)
MyBase.OnClosing(cancelEventArgs)
If Not cancelEventArgs.Cancel Then
If State = AppState.Autorized AndAlso MessageService.ShowMessage("Do you really want to close the application?", "Confirm", MessageButton.YesNo) = MessageResult.No Then
cancelEventArgs.Cancel = True
End If
End If

此代碼檢查當前的 State 屬性值，僅在授權通過時顯示確認消息。 如果最終用戶尚未登錄并決定關閉應用程序，則不會顯示任何確認信息。 這就是為什么 State 屬性不是布爾值，而是接受自定義 AppState 枚舉器的值的原因。 可能存在三種應用狀態(tài)：

• Authorized（已授權） - 用戶憑據(jù)有效。 主表單是可見的，嘗試關閉它應該會顯示確認消息，最終用戶可以單擊 ‘No’ 來保持應用程序運行。
• NotAuthorized - 輸入了用戶憑據(jù)，但未通過驗證。 主應用程序表單保持透明，登錄表單重新顯示。
• ExitQueued - 未輸入用戶憑據(jù)，登錄表單已關閉，應用程序應在沒有任何確認對話框的情況下終止。

6. 您的登錄表單現(xiàn)已準備就緒。可以通過為密碼編輯器設置特定的 RepositoryItemTextEdit.PasswordChar 來裝飾它，在主表單上反映登錄用戶的名稱，并將按鈕添加到主視圖的網(wǎng)格控件中，以便您重新登錄等，下面的代碼說明了 怎么做。

C#

//LoginView.cs
PasswordTextEdit.Properties.PasswordChar = '*';

//MyDbContextViewModel.partial.cs
protected void OnStateChanged() {
this.RaiseCanExecuteChanged(x => x.Logout());
if(State == AppState.Authorized)
Messenger.Default.Send<string>(loginViewModel.CurrentUser.Login);
else
Messenger.Default.Send<string>(string.Empty);
}

public void Logout() {
State = AppState.ExitQueued;
System.Diagnostics.Process.Start(System.Windows.Forms.Application.ExecutablePath);
}

public bool CanLogout() {
return State == AppState.Authorized;
}
//MainView.cs
Messenger.Default.Register<string>(this, OnUserNameMessage);
fluentAPI.BindCommand(biLogout, x => x.Logout());

void OnUserNameMessage(string userName) {
if(string.IsNullOrEmpty(userName))
this.Text = "Expenses Application";
else
this.Text = "Expenses Application - (" + userName + ")";
}

VB.NET

'LoginView.vb
PasswordTextEdit.Properties.PasswordChar = "*"c

'MyDbContextViewModel.partial.vb
protected void OnStateChanged()
Me.RaiseCanExecuteChanged(Sub(x) x.Logout())
If State = AppState.Authorized Then
Messenger.Default.Send(Of String)(loginViewModel.CurrentUser.Login)
Else
Messenger.Default.Send(Of String)(String.Empty)
End If

public void Logout()
State = AppState.ExitQueued
System.Diagnostics.Process.Start(System.Windows.Forms.Application.ExecutablePath)

public Boolean CanLogout()
Return State = AppState.Authorized
'MainView.vb
Messenger.Default.Register(Of String)(Me, AddressOf OnUserNameMessage)
fluentAPI.BindCommand(biLogout, Function(x) x.Logout())

void OnUserNameMessage(String userName)
If String.IsNullOrEmpty(userName) Then
Me.Text = "Expenses Application"
Else
Me.Text = "Expenses Application - (" & userName & ")"
End If

DevExpress WinForm | 下載試用

DevExpress WinForm擁有180+組件和UI庫，能為Windows Forms平臺創(chuàng)建具有影響力的業(yè)務解決方案。DevExpress WinForms能完美構建流暢、美觀且易于使用的應用程序，無論是Office風格的界面，還是分析處理大批量的業(yè)務數(shù)據(jù)，它都能輕松勝任！

更多產(chǎn)品正版授權詳情及優(yōu)惠，歡迎咨詢

DevExpress技術交流群6：600715373      歡迎一起進群討論