獲取工具下載 - DevExpress v21.2

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

1. 您的用戶數(shù)據(jù)庫實(shí)現(xiàn)方式可能會(huì)有所不同，對(duì)于示例應(yīng)用程序，您可以定義以下簡單類：

C#

public class User {
public string Login { get; set; }
public string Password { get; set; }
}

VB.NET

Public Class User
Public Property Login() As String
Public Property Password() As String
End Class

…以及以下存儲(chǔ)用戶憑據(jù)的類。

C#

static class CredentialsSource {
static System.Collections.Hashtable credentials;
static CredentialsSource() {
credentials = new System.Collections.Hashtable();
credentials.Add("Guest", GetHash(null));
credentials.Add("John", GetHash("qwerty"));
credentials.Add("Administrator", GetHash("admin"));
credentials.Add("Mary", GetHash("12345"));
}
internal static bool Check(string login, string pwd) {
return object.Equals(credentials[login], GetHash(pwd));
}
static object GetHash(string password) {
return password;
}
internal static System.Collections.Generic.IEnumerable<string> GetUserNames() {
foreach(string item in credentials.Keys)
yield return item;
}
}

VB.NET

Friend NotInheritable Class CredentialsSource

Private Sub New()
End Sub

Private Shared credentials As System.Collections.Hashtable
Shared Sub New()
credentials = New System.Collections.Hashtable()
credentials.Add("Guest", GetHash(Nothing))
credentials.Add("John", GetHash("qwerty"))
credentials.Add("Administrator", GetHash("admin"))
credentials.Add("Mary", GetHash("12345"))
End Sub
Friend Shared Function Check(ByVal login As String, ByVal pwd As String) As Boolean
Return Object.Equals(credentials(login), GetHash(pwd))
End Function
Private Shared Function GetHash(ByVal password As String) As Object
Return password
End Function
Friend Shared Iterator Function GetUserNames() As System.Collections.Generic.IEnumerable(Of String)
For Each item As String In credentials.Keys
Yield item
Next item
End Function
End Class

2. 使用 DataLayoutControl 創(chuàng)建一個(gè) LoginView 用戶控件，就像使用詳細(xì)視圖一樣。 不要忘記將數(shù)據(jù)綁定的 DataSourceUpdateMode 設(shè)置為 OnPropertyChanged，否則按“Enter”鍵將傳遞一個(gè)空密碼，因?yàn)榫庉嬈魅蕴幱诮裹c(diǎn)狀態(tài)。 要提高登錄表單的可用性，請(qǐng)使用編輯器的智能標(biāo)簽將顯示用戶名的編輯器類型更改為 LookUpEdit。

3. 對(duì)于本次登錄View相關(guān)的ViewModel，可以使用Scaffolding Wizard生成或者手動(dòng)實(shí)現(xiàn)，以下代碼說明了最簡單的 LoginViewModel 實(shí)現(xiàn)。

C#

using System.Collections.Generic;
using DevExpress.Mvvm.POCO;
using MVVMExpenses.Models;

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>();
}
}

VB.NET

Imports System.Collections.Generic
Imports DevExpress.Mvvm.POCO
Imports MVVMExpenses.Models

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

在此 ViewModel 中，定義了兩個(gè)屬性：存儲(chǔ)當(dāng)前登錄用戶的 CurrentUser 屬性和指定輸入憑據(jù)是否已通過驗(yàn)證的布爾值 IsCurrentUserCredentialsValid 屬性。

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