Show a List of Users Allowed to Read an Object

• Mar 24, 2022
• 2 minutes to read

This topic demonstrates how to create an Action to display a list of users whose roles allow reading a specific object.

1. Create a View Controller with PopupWindowShowAction. This Action displays a list of users in a pop-up window.
2. In the CustomizePopupWindowParams event handler, use the GetSecurityStrategy(XafApplication) method to get a Security Strategy instance.
3. Get the ListView’s Object Space and use its CreateListView(Type, Boolean) method to create a new List View for user objects.
4. Use the IObjectSpace.GetObjects<T>() method to get a list of all users.
5. To check if each user has permissions that allow reading a target object, use the CanReadByUser(SecurityStrategy, IPermissionPolicyUser, Object, String) method.
6. Customize the List View’s Collection Source and set the CustomizePopupWindowParamsEventArgs.View property to the created List View.

C#

using System;
using System.Collections.Generic;
using DevExpress.Data.Filtering;
using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Actions;
using DevExpress.ExpressApp.Security;
using DevExpress.Persistent.Base;
using DevExpress.Persistent.BaseImpl.PermissionPolicy;
// ...
public class DisplayUsersWithObjectAccessController : ViewController<DetailView> {
    PopupWindowShowAction displayUsersAction;
    public DisplayUsersWithObjectAccessController() : base() {
        displayUsersAction = new PopupWindowShowAction(this, "DisplayUsersWithObjectAccess", PredefinedCategory.View);
        displayUsersAction.ImageName = "Context_Menu_Show_In_Popup";
        displayUsersAction.CustomizePopupWindowParams += DisplayUsersAction_CustomizePopupWindowParams;
    }
    private void DisplayUsersAction_CustomizePopupWindowParams(object sender, CustomizePopupWindowParamsEventArgs e) {
        Type userType = typeof(PermissionPolicyUser);
        ListView listView = Application.CreateListView(userType, true);
        SecurityStrategy securityStrategy = Application.GetSecurityStrategy();
        List<IPermissionPolicyUser> users = new List<IPermissionPolicyUser>();
        IObjectSpace objectSpace = listView.ObjectSpace;
        foreach (IPermissionPolicyUser user in objectSpace.GetObjects<PermissionPolicyUser>()) {
            if (securityStrategy.CanReadByUser(user, View.CurrentObject)) {
                users.Add(user);
            }
        }
        listView.CollectionSource.Criteria["UsersWithObjectAccess"] = new InOperator(objectSpace.GetKeyPropertyName(userType), users);
        e.View = listView;
    }
}

VB.NET

Imports System
Imports System.Collections.Generic
Imports DevExpress.Data.Filtering
Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Actions
Imports DevExpress.ExpressApp.Security
Imports DevExpress.Persistent.Base
Imports DevExpress.Persistent.BaseImpl.PermissionPolicy
' ...
Public Class DisplayUsersWithObjectAccessController
    Inherits ViewController(Of DetailView)
    Private displayUsersAction As PopupWindowShowAction
    Public Sub New()
        MyBase.New()
        displayUsersAction = New PopupWindowShowAction(Me, "DisplayUsersWithObjectAccess", PredefinedCategory.View)
        displayUsersAction.ImageName = "Context_Menu_Show_In_Popup"
        AddHandler displayUsersAction.CustomizePopupWindowParams, AddressOf DisplayUsersAction_CustomizePopupWindowParams
    End Sub
    Private Sub DisplayUsersAction_CustomizePopupWindowParams(ByVal sender As Object, ByVal e As CustomizePopupWindowParamsEventArgs)
        Dim userType As Type = GetType(PermissionPolicyUser)
        Dim listView As ListView = Application.CreateListView(userType, True)
        Dim securityStrategy As SecurityStrategy = Application.GetSecurityStrategy()
        Dim users As New List(Of IPermissionPolicyUser)()
        Dim objectSpace As IObjectSpace = listView.ObjectSpace
        For Each user As IPermissionPolicyUser In objectSpace.GetObjects(Of PermissionPolicyUser)()
            If securityStrategy.CanReadByUser(user, View.CurrentObject) Then
                users.Add(user)
            End If
        Next user
        listView.CollectionSource.Criteria("UsersWithObjectAccess") = New InOperator(objectSpace.GetKeyPropertyName(userType), users)
        e.View = listView
    End Sub
End Class

The following image shows the result:

Note

Refer to the following help topic to see other methods to check a user’s or role’s permissions: Determine if the Current User Has Specific Permissions.