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。在本節教程中著重討論了如何實現此任務，這基本上是附加應用程序功能的一部分。

1. 您的用戶數據庫實現方式可能會有所不同，對于示例應用程序，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

…以及以下存儲用戶憑據的類。

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 創建一個 LoginView 用戶控件，就像使用詳細視圖一樣。 不要忘記將數據綁定的 DataSourceUpdateMode 設置為 OnPropertyChanged，否則按“Enter”鍵將傳遞一個空密碼，因為編輯器仍處于焦點狀態。 要提高登錄表單的可用性，請使用編輯器的智能標簽將顯示用戶名的編輯器類型更改為 LookUpEdit。

3. 對于本次登錄View相關的ViewModel，可以使用Scaffolding Wizard生成或者手動實現，以下代碼說明了最簡單的 LoginViewModel 實現。

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，定義了兩個屬性：存儲當前登錄用戶的 CurrentUser 屬性和指定輸入憑據是否已通過驗證的布爾值 IsCurrentUserCredentialsValid 屬性。

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