Web - How to avoid issues with data-bound controls due to missing or non-unique key values

Check out the Web - How to avoid issues with data-bound controls due to missing or non-unique key values KB article to make sure that your business model is aligned with the best practices. Here is a short extract:

Symptoms

You may notice the following side-effects in a Web ListView while it may work fine in WinForms:

- A wrong DetailView may be selected when an unsaved record is clicked in ListView;

- ListView may have no selection column;

- In inline edit or batch mode, all records may become selected or editable.

These effects are especially frequent in a non-persistent class ListView or a nested ListView for an aggregated details collection with newly added or unsaved records.

Explanation

All new records added to the ListView and not yet saved to the database will be assigned with a temporary key value (e.g. -1 or an empty Guid/String value depending on your key type). In a Web application, ListView uses a business class key property to identify records, because there is no way to access real business objects from the web browser. Hence, there is a requirement that each business object must have a unique value assigned to the key property. ASPxGridView and other data-bound controls require this for the correct operation of such features like selection, filtering, sorting, grouping and the standard XAF functionality that depends on them (see also ASPxGridBase > KeyFieldName). 

If a key property is missing in a business class completely or if a key property is not initialized with a unique value immediately after the record is created, these duplicate or invalid records may lead to a data-bound control malfunction as expected.

Please inform me of your health-check results!

Learning through reading the source code

I will start this post with the new Visual Studio 2017 function, which I hope will be helpful for XAF developers too. I have both RTM and Preview versions installed, but I am mostly using the latter one for testing. The new function I spotted in their change logs is called "View decompiled source definitions instead of metadata (C#)".

As you can guess from its name, it changes the very often used "Go To Definition" command (F12) so that it displays the actual code of a C# type or member who's source code is unavailable - very useful and convenient, IMHO. It is decompiled using ILSpy, the tool I have already been using for years as default program association for opening *.dll files -  partially the reason of why this news got my attention. This experimental feature is new in Visual Studio 2017 version 15.6 preview 2+ and it must be turned on explicitly using the Tools > Options  >  Text Editor > C# > Advanced > Enable navigation to decompiled sources menu item. 

Beware of the failures when uploading JPEG/JPG images using the System.Drawing.Image type properties - XAF ASP.NET WebForms v17.2.5

I want to draw your attention to the T604395: Web - JPEG/JPG images cannot be uploaded to properties of the System.Drawing.Image type

 issue, which is already fixed in XAF v17.2.6. 

We apologize for the inconvenience, and if you cannot wait for the hotfix or did not plan to spend additional time on upgrade right now, please consider using the workarounds.

Important notes and workarounds

From v14.2, Image Property Editors (both WinForms and ASP.NET) support images saved as byte array objects (in addition to previously supported System.Drawing.Image objects). This allows us to significantly decrease web server memory consumption because the byte array can contain an image in a compressed format and the server does not have to unpack it. The previous approach with the System.Drawing.Image type property is still supported, but we recommend that you migrate to the byte array storage to improve performance. Refer to the BLOB Image Properties in XPO  and How to change the image property type from System.Drawing.Image to byte array help topics for more details. 

Database maintenance recommendations for applications created or used with XPO or XAF

We have published a KB article that may help you protect the end application's data and keep the system reliable, fast and running smoothly as time goes on, application data grows and other factors are involved during the application's use in production:

https://www.devexpress.com/kb=T572322

I hope you find this information helpful.

See Also:
How to measure and improve the application's performance

How to implement the CreatedBy, CreatedOn and UpdatedBy, UpdatedOn properties in a business class

I would like to promote a KB article, which may be interesting for users who are just getting started with our application framework. This information is actually not new and it was already available in the FAQ and Reference sections of our online documentation as well as the support knowledge base.

https://www.devexpress.com/kb=K18352

I must emphasize that there are actually many ways to implement such auditing properties, and your current code may differ from what we show. For instance, one may declare it as "internal  set {...}" or use the PersistentAlias attribute. Just do not be at all concerned. 

You are welcome to share your own implementations in post comments - maybe we can vote for the most concise and beautiful code, eh?:-P

What happens when the current user is deleted (by himself/herself or another user) while still using the application?

Deletion of the user who is actively using the app is NOT handled by our security module at the moment (e.g., NullReferenceException and other errors may occur). That is mainly because this operation is very rare, and so far we have not received real-life scenarios from our users where this could be useful. Moreover, deleting by accident is already prevented by showing a confirmation message by the standard DeleteObjectsViewController > DeleteAction.

Refer to this Support Center ticket for more considerations and possible custom solutions.

Your feedback is needed!

Even though we do not provide ready solutions for this specific scenario, we will be more than happy to learn more about your experience in this regard to consider improvements to our product for the future. If you needed to handle such scenarios on your own, please elaborate more on your real-life requirements and implemented solutions. Thanks in advance.

Performance tuning of the saving/validation process using the PersistenceValidationController events

Regardless of how good and sophisticated your development tools are, real production use often imposes research and solving speed issues. In this tip, I will talk about tuning the Validation Module to do its best when saving a master object exposing  large collections of aggregated data. 

By default, aggregated objects are considered to be an integral part of a master object, and thus, they should be validated together with the master object, which may take significant time if you have hundreds or thousands of complex detail records. The entire detail collection will be loaded and validated in this instance.

The good news is that XAF is very flexible and has a customizable framework that provides many ways to intercept this validation process. 

Linking XAF security roles and Active Directory Security Groups by name

We have recently created a new help topic devoted to one of the popular scenarios our users described: How to: Assign the Same Permissions for All Users of an Active Directory Group. This topic demonstrates how to map XAF security roles to AD groups. When a user logs on for the first time, existing roles with names matching the user's AD group names are automatically assigned. If the user membership in AD groups was modified, the associated roles collection will be updated accordingly on the next logon. Take special note that the corresponding XAF security roles with required permissions and matching the names of AD groups must be created first!

This article also required for us to avoid confusion with the AuthenticationActiveDirectory component name, because it does not support Active Directory Security Groups out of the box.  What this component does is just allow logging by the currently logged Windows user automatically or without the logon form.  To initialize the created XAF security user record, the AuthenticationActiveDirectory authentication uses the WindowsIdentity.Name property of an object obtained via the static WindowsIdentity.GetCurrent method to get a user name in the DOMAIN\USERNAME format.

I want to point out one implementation aspect that might be unclear: why did we create a AuthenticationActiveDirectory descendant instead of handling the CustomCreateUser event, which looks simpler? The main reason for using the descendant is that with it, the synchronization of XAF security roles is easier to implement when AD groups are updated.

I hope you find this example helpful. Please let us know in comments if you experienced a similar scenario and describe how you are currently handling it. Thanks in advance!

XPQuery changes regarding non-persistent properties in v17.1

In version 17.1, we have improved error detection in XPQuery when non-persistent properties are used in it. Previously, such queries didn't work (either failed with various exceptions or worked incorrectly) and thus there were hidden errors in your programs. Now, we throw an exception that describes which non-persistent properties are used in XPQuery to help diagnosing these errors. If such properties are used intentionally, consider implementing them using PersistentAliasAttribute or adding the ToList method call to explicitly process these properties on the client side.

Refer to the https://www.devexpress.com/kb=T523335 KB Article for examples and more details.

Web - How to preserve the FullTextSearch Action filter after opening details for a record and returning back to ListView

I want to repost an interesting ASP.NET WebForms scenario and a solution for it I provided to a customer yesterday. Watch this video to see how this works:

If you are interested in having something like this, check out this Support Center thread for a relatively simple Controller.

How to copy or clone an existing report

Today I've updated a related Support Center article where I listed several possible ways of accomplishing this task. 

I would appreciate it if you describe in comments which approach # you are using yourself or describe your own solution, if it is not listed there. Thanks in advance!

More secure password generation algorithms for built-in security system classes are available in XAF v16.2 and v17.1

We have offered new options for those of you who need to deploy apps to production environments with the FIPS policy enforced (e.g., government desktop computers or highly secured web servers). XAF APIs now support FIPS compliant algorithms for more secure user passwords encryption and images hashing. 

Please refer to the article below for more details and let me know what you think of it:

FIPS-compliance changes to the DevExpress.Persistent.Base.PasswordCryptographer and DevExpress.ExpressApp.Utils.ImageLoader classes 

Improving UX with Grid List Editors by disabling ALL unsupported operations for non-persistent columns in server modes (XAF v16.2.6) - YOUR FEEDBACK IS NEEDED!

In server modes, grid controls perform operations like sorting, grouping, filtering, etc. on the data store side to guarantee the best performance. Thus, columns bound to non-persistent properties (their values exist only in the client memory at runtime) cannot be used for such server-based operations and can cause exceptions (learn more...). Some of them can be detected only in the end application after navigating to a problematic grid at runtime.

With XAF 16.2.6, to prevent these situations, we have improved column creation logic in our Grid List Editors for Windows and the Web. In particular, we have disabled all server-based operations (sorting, filtering, grouping) for non-persistent properties in the ASP.NET WebForms ASPxGridListEditor and WinForms GridListEditor when DataAccessMode = Server or InstantFeedback. 

Technically, it means the following:

    1) The grid's Find Panel does not take non-persistent properties into account.

    2) The grid's Filter Editor does not display non-persistent properties in the properties tree.

    3) The grid's Auto Filter Row feature is not available for non-persistent columns.

    4) Grid column headers for non-persistent columns do not allow end-users to filter, sort, group.

See this video recorded from the WinForms version of our MainDemo:

Take special note that in XPO, calculated non-persistent properties defined using PersistentAliasAttribute or CalculatedAttribute can still be used without problems for server-based operations as previously. The only PersistentAlias attribute scenario, which may still not lead to disabled server-side operations, is when you have an aliased reference property and a grid column with a complex property path like:
YourPersistentAliasReferenceProperty.SomeNestedProperty1.SomeNestedPropertyN.
Such properties will be treated as regular non-persistent properties for now or you can disable our improvement using the feature toggle below.
For EF, calculated properties defined using CalculatedAttribute are still unsupported and treated as regular non-persistent properties mentioned above.

I do not need this behavior. How do I disable it?
With v16.2.7 (or, after installing this hot fix), you can set the PreventServerSideOperationsForNonPersistentMembers property of the DevExpress.ExpressApp.Editors > ColumnsListEditor  class to False in the overridden OnActivated method of a custom ViewController for a required ListView. Refer to the following example:

[C#]
using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Editors;

namespace MainDemo.Module.Controllers {
    public class S31714_FeatureToggle : ViewController<ListView> {
        protected override void OnActivated() {
            base.OnActivated();
            ColumnsListEditor columnsListEditor = View.Editor as ColumnsListEditor;
            if(columnsListEditor != null) {
                columnsListEditor.PreventServerSideOperationsForNonPersistentMembers = false;
            }
        }
    }
}

[VB.NET]
Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Editors

Namespace MainDemo.Module.Controllers
    Public Class S31714_FeatureToggle
        Inherits ViewController(Of ListView)

        Protected Overrides Sub OnActivated()
            MyBase.OnActivated()
            Dim columnsListEditor As ColumnsListEditor = TryCast(View.Editor, ColumnsListEditor)
            If columnsListEditor IsNot Nothing Then
                columnsListEditor.PreventServerSideOperationsForNonPersistentMembers = False
            End If
        End Sub
    End Class
End Namespace

Filtering - How to search objects within ListPropertyEditor or enabling the standard FullTextSearch Action for nested ListView

Just wanted to repost a nice tip from the old SC ticket, which I updated today:

By default, the standard FullTextSearch Action is mapped to the "FullTextSearch" category or Action Container that is physically present in the main, detail and lookup control templates. Historically, it is missing in the nested frame template, which is typically used for ListPropertyEditor, DetailPropertyEditor or DashboardViewItem, mainly not to overload their toolbar with a large text box.

If you still need full text search functionality in nested frame templates, you can consider the following solutions:

1. Create a custom nested frame template as per the Template Customization. article and manually add the "FullTextSearch" action container into it. This solution appears to be the most difficult from the implementation and further maintenance points of view.

2. Customize the default mapping of Actions to the default Action Containers in the Application Model. To do this, invoke the Model Editor and follow this video:

Take special note that It is important to make a copy of the Action definition and place it into the Action Container (e.g., Link), which is NOT present in the main, detail and lookup control templates to avoid duplication of Actions in the UI:

This solutions appears to be the easiest one from all points.

3. Enable native filtering features of the underlying grid, tree and other data bound controls used in nested ListView. For instance, the Find Panel or Auto Filter Row features also provide very good filtering experiences many of your clients will love.  The only disadvantage (which can be noticeable in advanced scenarios only) is that with the standard FullTextSearch Action you can provide common customizations for root and nested ListView using the events and other extensibility points of our FilterController, while for the native control features, you will likely have to implement platform-dependent customizations.

How to change an Application Model option globally or for multiple nodes

I have recently updated one of the articles on the subject in our support knowledge base and wanted to test-drive this content with you: https://www.devexpress.com/kb=T271022

Since the Application Model basically represents a skeleton of the application UI, based on which visual controls for supported platforms are created at runtime, updates to various options in the source UI metadata (both at design time and runtime) can be a good and often platform-agnostic alternative to customizing underlying controls directly in Controllers or other UI entities (examples: one, two, three). The most difficult thing is to perform this update at the right moment or using the right event in the View life cycle!

Even though this may sound like a quite an advanced topic, this is one of the core concepts for our framework, which I recommend you get familiar with.

Your feedback is welcome, as always!

We also hope to use this KB as a base for future updates of the online documentation at  Concepts > Application Model  for easier discoverability, so your early feedback on the main methods I described is welcome. In particular, I would greatly appreciate your comments on whether you experienced the scenarios needed runtime Application Model updates and exactly which techniques you used (e.g., #2.1, 2.2 or all ).

How to refresh View appearance after making changes to the Application Model in code

With XAF v16.2.4, you can apply Application Model changes to a View without recreating it. To do this, save the Frame's View to a variable and then unlink it from the Frame by passing null to the SetView method. After that, make the required changes to the model, call the LoadModel method with the false parameter and then set the saved View back to the Frame using the SetView method. Here is the generic code illustrating this pattern:

View view = Frame.View;

if(Frame.SetView(null, true, null, false)) {

    // Make required changes with the model here. 

    // ... 

    view.LoadModel(false);

    Frame.SetView(view);

}

You can find a full ViewController code for accomplishing the two most popular WinForms scenarios benefiting from this capability in the https://www.devexpress.com/kb=S173664 article (switching a ListView editor type and MasterDetailMode). 
This video also illustrates how it works in the application UI in action. 

Leave a comment if this is something you are going to try right now!

As always, please report any issues using the https://www.devexpress.com/ask service. Thanks in advance!

How to replace XAF exception handling with Logify

I would like to promote a KB article on the subject, which I published yesterday right after receiving a customer request in response to the recent DevExpress Logify: a New Exception Reporting Tool  blog post.

The XAF article describes three typical ways to integrate Logify into an XAF app. Here I want to note that while the third option with a custom trace listener may look a bit complicated now, it is possible that the Logify team will come up with a built-in trace listener in the future (at least I talked about this with the responsible team and they also said that they thought about such an option). This way you will be able to plug-in this listener in an XAF app using a few lines in the configuration file or in code as per How to: Create and Initialize Trace Listeners (MSDN).

We would greatly appreciate it if you inform us of which XAF integration approach (# 1,2,3 or any other) you eventually implemented in your project and how it all worked for you. Thanks in advance!

New and updated XAF videos

I am glad to announce that the XAF team have published several new videos in DevExpress channel. These videos demonstrate the most attractive features from the What's New in XAF v16.2 list.

XAF Mobile Platform (CTP)

With this video, you can learn how to add a mobile client for your XAF application. This is the updated version of the previously published video. It demonstrates the following mobile enhancements introduced in 16.2

1. New UI layouts optimized for desktop and tablet devices.
2. Improved look and feel.
3. Application Simulator no longer requires an internet connection.
4. 'Active' and 'Enabled' action states are now context-dependent.

A WinForms example for collapsing/expanding layout groups and persisting their state

As you probably know, the New Web UI was recently enhanced with built-in options for this scenario. Today, I have updated the https://www.devexpress.com/kb=S135134 thread with a WinForms solution:

Please don't hesitate to write to us about each use case scenario that requires additional code to adjust the layout controls to better meet your business needs. My team and I will be more than happy to research them and see how to manage this situation better at the XAF or DevExpress component level. For instance, here we are thinking about providing platform-agnostic Application Model extensions for managing this task for Windows and the Web.

A custom XAF PropertyEditor example based on the WinForms TimeSpanEdit component

As you know, XAF is very flexible and provides many ways of integrating custom controls for various scenarios; e.g., where something is not covered by the default controls pack: Concepts > UI Construction > Using a Custom Control that is not Integrated by Default

As far as our framework development flow is concerned, it is absolutely natural to perform this sort of customizations, and this extensibility was baked in from the very beginning for XAF users. For instance, there is a built-in WinForms TimeSpanPropertyEditor class for representing and editing System.TimeSpan type properties in the standard delivery:

        public TimeSpan TimeSpanProperty {

            get { return GetPropertyValue<TimeSpan>("TimeSpanProperty"); }

            set { SetPropertyValue<TimeSpan>("TimeSpanProperty", value); }

        }

Technically, our TimeSpanPropertyEditor just wraps a TextEdit descendant from the XtraEditors Library and provides a custom mask for it. One may want to use another visual control for the same task (e.g., the TimeSpanEdit control from the same XtraEdititors library) and that is quite easy to implement in XAF. You can implement a custom PropertyEditor as per  Concepts > UI Construction > View Items > Implement Custom Property Editors