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Please follow the official XAF Team and XPO Team blogs, which are regularly updated by me and other DevExpress members.
Thanks, Dennis.
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In XAF, users of the Model Editor and Report Designer tools are likely to be affected by this issue. Well, advanced users who enabled the ShowPropertyGrid property in the layout control or made custom PropertyGridControl integrations may be affected too - at least we all know a few😉

Our XtraVerticalGrid developers are aware of this problem and have already fixed it in v18.1.4 (it should be out in 1.5-2 weeks). In the meantime, the hotfix is already available for download at T638535: PropertyGridControl - The NullReferenceException is thrown when scrolling and an editor is active. Please accept sincerely apologies from our XAF, XtraReports and XtraVerticalGrid teams for all the inconvenience here.

Here is the error callstack for your reference:

System.NullReferenceException at DevExpress.XtraVerticalGrid.PGEditingState.MouseWheel(DevExpress.Utils.MouseWheelScrollClientArgs) at DevExpress.XtraVerticalGrid.BaseHandler.DevExpress.Utils.IMouseWheelScrollClient.OnMouseWheel(DevExpress.Utils.MouseWheelScrollClientArgs) at DevExpress.Utils.MouseWheelScrollHelper.OnScrollLine(DevExpress.Utils.DXMouseEventArgs, Int32, Boolean) at DevExpress.Utils.MouseWheelScrollHelper.OnMouseWheel(System.Windows.Forms.MouseEventArgs) at DevExpress.XtraVerticalGrid.BaseHandler.OnMouseWheel(System.Windows.Forms.MouseEventArgs) at DevExpress.XtraVerticalGrid.VGridControlBase.OnMouseWheelCore(System.Windows.Forms.MouseEventArgs) at DevExpress.XtraEditors.Container.EditorContainer.OnMouseWheel(System.Windows.Forms.MouseEventArgs) at System.Windows.Forms.Control.WmMouseWheel(System.Windows.Forms.Message ByRef) at System.Windows.Forms.Control.WndProc(System.Windows.Forms.Message ByRef) at DevExpress.XtraEditors.Container.EditorContainer.WndProc(System.Windows.Forms.Message ByRef) at DevExpress.XtraVerticalGrid.VGridControlBase.WndProc(System.Windows.Forms.Message ByRef) at System.Windows.Forms.Control+ControlNativeWindow.OnMessage(System.Windows.Forms.Message ByRef) at System.Windows.Forms.Control+ControlNativeWindow.WndProc(System.Windows.Forms.Message ByRef) at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr, Int32, IntPtr, IntPtr)


Tip 1: The How to obtain a design-time exception call stack KB article describes how to locate these important error details, especially if your Visual Studio crashed. This information is helpful when submitting to support. BTW, to improve your chances of getting a faster and helpful answer from support, check these related tips as well:
   How do I ask a good question? (StackOverFlow)
   How to Report Bugs Effectively (Simon Tatham)
   A request for simple example programs (Julian Bucknall)
   Collect and Analyze the Diagnostic Information (XAF documentation)


Tip 2: When you located the call stack information and determined from it that an exception is raised from DevExpress code, I recommend you search for one or several topmost call stack method names in our support database. This behavior might be reported by someone else, e.g.: https://www.google.com/search?q=PGEditingState.MouseWheel

The future of old RichTextPropertyEditor and HtmlPropertyEditor with the introduction of the new Office-inspired Word Processing Module - YOUR FEEDBACK IS NEEDED!!!

Why bothering?

As many of you already heard, we are shipping the Office module with the Rich Text Editor in v18.1. It allows end-users to create, load, change, print, save and convert documents in different formats, including HTML. At this stage, this new module is for WinForms only. We see ways to support more Office functionality and cover other platforms in the future.

As you know, there are two very old XAF Property Editors, which perform similar functions, but with lower quality. They are both based on standard Microsoft controls:

DevExpress.ExpressApp.HtmlPropertyEditor.Win.HtmlPropertyEditor - this is a part of HTML Property Editor Module that integrates the System.Windows.Forms.WebBrowser component. 

DevExpress.ExpressApp.Win.Editors.RichTextPropertyEditor - this is a part of the standard DevExpress.ExpressApp.Win module that integrates the System.Windows.Forms.RichTextBox component.

We created them almost 10 years ago when DevExpress did not provide controls with similar functions. Today, their usage is not justified also because of missing High DPI support, nice icons and useful functions like Mail Merge. Workarounds can be implemented for these standard controls too, but it does not make much sense to invest our resources into this when much better options are already available. These editors have not recently received updates in other areas anyway. This is still a maintenance work for our team that could have been spent on something else.

What we want to change and how?

XAF WinForms v17.2.6 - Beware of missing icons in inactive tabs after restoring the Tabbed MDI layout

I want to draw your attention to the T611846: DocumentManager - TabbedView does not show images for documents issue already fixed in the XtraBars Suite and which XAF WinForms Tabbed MDI users might encounter after upgrading to v17.2.6. The number of users who already hit this exceeded a certain threshold, and the known issues section in the What's New documentation or manual searching the Support Center may not help effectively discover it yourself. So, I am posting this here to widely inform those who have not yet upgraded their XAF/WinForms projects to v17.2.6.

You can also download a hotfix build from here.

Please accept sincerely apologies from our XAF and XtraBars teams for all the inconvenience here.

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. 

Beware of the PhoneGap's Camera and Geolocation plugins version update

I wanted to warn early adopters of the XAF Mobile UI of the recent change in https://build.phonegap.com due to the updated version of two main plugins that may stop your camera or geolocation functionality on real devices:

https://www.devexpress.com/issue=T575763

Check this thread for a temporary workaround until we release new minor versions with the required changes. We apologize for all the inconvenience here, because we must have been sticking to a fixed version instead of the latest one when building the application package.

Beware of the situation when a signed assembly with a business type used in the dashboard changes its version

I wanted to inform our Dashboard module users about a situation, which we missed originally:

DashboardObjectDataSource serializer fails to load a data source type when signed assemblies with a changed version are used

As you understand, it may occur only when target business types used in XML dashboard definitions with ObjectDataSource are from signed assemblies and the assembly version changes, e.g. when you deliver a new app version to the client:

 <DataSources>
    <ObjectDataSource ComponentName="dashboardObjectDataSource1">
      <Name>Object Data Source 1</Name>
      <DataSource Type="YourNamespace.YourObjectType, YourAssemblyName, Version=17.1.6498.1953, Culture=neutral, PublicKeyToken=YourPublicKeyToken" />
    </ObjectDataSource>
  </DataSources>

Currently, we recommend XAF application developers try a couple of solutions described in that thread, but they are not final solutions. We are currently reviewing them from the security point of view to make sure that the app won't be broken by passing another non-signed dll. For now, this does not seem to be the case, because business type information is obtained using the ReflectionHelper API from the already loaded assemblies, which are protected by the default .NET mechanisms. We just want to double-check or see if there are more suitable options. Ideally, I wish this to be working transparently for an application developer without the need to resolve any assemblies or types manually.

Your feedback is needed!

Have you experienced this behavior in your Dashboard apps? How do you currently cope with it? If there are existing solutions, share their details and also elaborate on their costs. Your feedback is greatly appreciated.

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. 

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.

XAF ASP.NET WebForms - Beware of the FormatException (Input string was not in a correct format) when clicking a record in a popup ListView

I want to draw your attention to the T514321: ASPxGridListEditor - FormatException is thrown when selecting an object in a lookup ListView shown from an aggregated collection issue, which is already fixed in XAF for v16.2.7/17.1.4. 

If you came across a similar issue (check the call stack), the highlighted thread contains the hotfix installation for v17.1.

Tip:

When you experienced an exception in DevExpress code, I recommend you locate its callstack and search for one or several topmost method names in our support database, because this behavior might be reported by someone else: https://search.devexpress.com/?q=ASPxGridViewContextMenu.SelectObject&m=SupportCenter

In addition, I recommend checking the Known Issues sections in our What's New documentation:

    all XAF issues that were created in v2016 vol 2.6.

    all XAF issues that were created in v2017 vol 1.3

XAF ASP.NET WebForms v16.2 - Beware of the ArgumentException (An item with the same key has already been added) in Web Dashboards

I want to draw your attention to the T511396: Web Dashboards - ArgumentException - An item with the same key has already been added issue, which is already fixed in XAF for v16.2.7. 

This error can occur if the application model contains different BO Models with the same Caption and is visible in dashboards.

If you came across a similar issue (check the call stack), the highlighted thread contains a simple temporary solution (make captions different or remove the VisibleInDashboardsAttribute from classes that are not required in dashboards)  + hotfix installation.

The Frame.GetController method may return null when the XafApplication.OptimizedControllersCreation property is set to True

With XAF v17.1, Solution Wizard sets the XafApplication.OptimizedControllersCreation property to True for newly created XAF projects (existing projects will not be affected). 

To avoid possible null reference exceptions in nested List Views, always check if the Frame.GetController<ControllerType> method result is not null when the OptimizedControllersCreation property is true. The latter option is required to get faster loading of DetailView when it contains a lot of nested ListView items (learn more...).

Our online documentation was already updated to describe this optimization specificity and add these null-checks everywhere; e.g., check theses examples: one, two. KB articles, Code Examples and popular Support Center tickets are not yet updated, but we hope to do this with time as well. Should you find missing checks in our learning materials, please contact us.

Web Layout Manager improvements and important changes in XAF v17.1

In the 17.1 version, we have improved the scenario of loading the ASPxPageControl tab content when XafApplication.DelayedViewItemsInitialization equals True and the Conditional Appearance module is involved. So, if you encountered missing or not fully loaded tab contents in this configuration, and had to previously adjust the application-level DelayedViewItemsInitialization or View-level DelayedItemsInitialization options to avoid this behavior (learn more...), starting with v17.1, it is possible to revert these options to True by default. 

Take special note that these improvements required us to introduce some changes, which may affect a very small group of users who created and registered custom layout group templates in WebLayoutManager. Frankly speaking, this was needed for very advanced scenarios (we could locate only a few cases in our large Support Center database), so we expect that the majority of XAF users will not be affected by these changes. Anyway, if you feel or know that you could have been affected, refer to the Web Layout Manager improvements and important changes in XAF v17.1 KB Article for more details.

BTW, have you ever created custom layout item and group templates for WebLayoutManager?:-) If so, please share your use-cases in comments. I am asking because it is quite possible that we already have better solutions for you (e.g., expandable/collapsible layout groups are already supported out-of-the-box)!

The latest XAF v16.2.6 hot fix build for missing collections in the filter editor and a few other issues

I wanted to draw your attention to the subject because the official v16.2.6 contained a few trending issues which were not covered by our automated tests till now:

http://downloads.devexpress.com/Share/DXP/170410/DevExpressComponents-16.2.6.17100.exe

Thankfully, we could provide quick fixes for them and also increased the number of unit and functional tests. Anyway, we apologize for all the inconvenience they might have caused you and your business.

The issues that can attract your attention most of all are:
T500881 - An exception thrown from a popup dialog unexpectedly terminates the whole application execution when debugging in Visual Studio

T498474 - Filter Editor - Collection properties are missing in the property list when DataAccessMode = Server or InstantFeedback after migrating to v16.2.6

Let me know if you experience any difficulties with this hot fix build.

BTW, consider checking the Known Issues section in our What's New documentation if you encounter an issue with our products, because we always inform our customers of such issues + there you can see reports from other clients. I hope you find this information helpful for the future.

XAF ASP.NET WebForms v16.2.5 - Beware of the missing Edit Action after navigating to dashboard items

I want to draw your attention to the T490025: WebEditDashboardController hides the Edit Action of ListViewController and doesn't reactivate it issue, which is already fixed in XAF for v16.2.6. This thread contains a simple temporary solution if you came across a similar use scenario (hotfix installation will be available later).

XAF WinForms v16.2.3 - Beware of exceptions when executing a ParametrizedAction (e.g. FullTextSearchAction) with TabbedMDI and Ribbon UI

I want to draw your attention to the T462973 - RibbonControl - NullReferenceException is thrown in the RibbonItemViewInfoCalculator.CalcEditItemViewInfo method issue already fixed in the XtraBars Suite for v16.2.3 and which XAF WinForms users might encounter after upgrading to v16.2.3. The number of users who already hit this exceeded a certain threshold, and the known issues section in the What's New documentation or manual searching the Support Center may not help effectively discover it yourself. Frankly speaking, we are a bit late with this warning, but it is still better to post this here to widely inform those who have not yet upgraded their XAF/WinForms projects to v16.2.3.

You can find more details and solution instructions in this article.

Please accept sincerely apologies from our XAF and XtraBars teams for all the inconvenience here.

Why can a DetailView be not editable or display empty values?

This small thing may hit even experienced XAFers, so I want to post this tip here for the future. In fact, I created a corresponding KB article a few months ago, but forgot to promote it in my blog. So, here we go: https://www.devexpress.com/kb=T382896

SYMPTOMS
1. You are creating a new detail form via the XafApplication.CreateDetailView API in a Web application, but it does not allow users to enter any information; e.g., they can't write/select anything into/from lookups. The View controls also look "readonly" or disabled. The same code produces an editable DetailView in WinForms, though.
2. Same readonly View editors as in the previous point, but the controls do not display any values either + the code does not work in both WinForms and ASP.NET apps.
3. You are opening a DetailView of an object that was deleted by another user. This way, this behavior is normal and expected as removed data can no longer be edited.

SOLUTIONS
1. Make sure you have set the DetailView.ViewEditMode property to the DevExpress.ExpressApp.Editors.ViewEditMode.Edit value. For example, check the snippet from this KB Article:

The GetObjectsNonReenterant error for security permissions with complex criteria - Fixed in v15.2.5

In v15.2.5 we have made improvements at both the XPO and XAF levels to avoid the Entering state 'GetObjectsNonReenterant' from state 'CommitTransactionNonReenterant, CommitChangesToDataLayer' is prohibited due to state 'CommitChangesToDataLayer' error that might occur while evaluating security permission criteria involving collections during the object saving procedure (S170995). Our previous attempt was unsuccessful and I apologize for this and all the inconvenience this has caused you and your business.

Our new low-level solution does not require extra options on your side, and I invite you to test a new 15.2 build containing these improvements: 

http://downloads.devexpress.com/Share/DXP/S170995/DevExpressComponents-15.2.4.15357.exe

I am looking forward to hearing from you on how these improvements work in your real projects after installing this build and running the Project Converter tool. Thanks in advance!

Making sure a property value is unique with XAF and XPO

I wanted to share a link to a hot Support Center discussion on the subject (it has now been unpublished by the author, sorry) with the community members as I believe this business task is not unique:-) and many others should be interested in knowing how to properly handle this.

I am going to detail technical considerations of possible solutions at the application UI and database levels depending on various configurations of your data model including inheritance mapping options (Table per Hierarchy or Table per Type) and soft deletion.

Application UI level

First of all, let's start from the UI part. How would a developer of an XAF app ensure that its end-users are not allowed to save records whose property value or combination of values are unique? 

As you know, XAF ships with a built-in validation module that provides a powerful and extendable validation engine and a large set of predefined attributes to configure common validation rules declaratively. To ensure uniqueness, you can first add the ValidationModule component into your XAF module or application via the designers and then choose from the two built-in rules: RuleCombinationOfPropertiesIsUnique and RuleUniqueValue (it is also possible to turn RuleObjectExists and RuleFromBoolPropert for the same task, but its use is not that straightforward use and I will not talk about it for now). Depending on your preferences, you can either annotate your data model classes with the corresponding code attributes, e.g.:

       [RuleUniqueValue]
       public string Name { ... }

or declare everything at the Application Model level via the Model Editor tool (learn more...). In addition, you can configure the rule's CriteriaEvaluationBehavior parameter, to specify whether to look for modified objects that are currently loaded in memory, in addition to objects in the database itself.

As a result, the XAF's validation engine will consider the rules you configured  when a data record is being saved (technically, when the View.ObjectSpace.Committing event is raised) and will throw ValidationException when uniqueness is violated. This is a special exception type, which is caught by other system controllers to display the validation error in a nice way in the UI:

This would be our topmost  or basic protection level as it handles user input only. It will not help avoid duplicates if the same data records are created in code by a developer who did not call one of the Validator.RuleSet.ValidateXXX methods. 

Beware of Windows update KB3025390 as it breaks EasyTest functionality in Internet Explorer 11

We were lucky enough to come across this issue when one day, almost all our internal functional tests (we use our in-house EasyTest engine) for XAF Web UI failed due to the following error:

    Type:       UnauthorizedAccessException
    Message:    Access is denied.

    Data:       0 entries
    Stack trace:

   at System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32 errorCode, IntPtr errorInfo)
   at System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(Int32 errorCode)
   at System.Runtime.InteropServices.CustomMarshalers.ExpandoViewOfDispatchEx.DispExInvoke(String pstrMemberName, Int32 MemberDispID, Int32 Flags, Binder pBinder, Object[] aArgs, ParameterModifier[] aModifiers, CultureInfo pCultureInfo, String[] astrNamedParameters)
   at System.Runtime.InteropServices.CustomMarshalers.DispatchExMethodInfo.Invoke(Object pObj, BindingFlags invokeAttr, Binder pBinder, Object[] aParameters, CultureInfo pCulture)
   at System.Runtime.InteropServices.CustomMarshalers.DispatchExPropertyInfo.GetValue(Object pObj, BindingFlags invokeAttr, Binder binder, Object[] aIndex, CultureInfo culture)
   at System.Reflection.PropertyInfo.GetValue(Object obj, Object[] index)
   at DevExpress.ExpressApp.EasyTest.WebAdapter.WebCommandAdapter.<>c__DisplayClasse.<GetIReflectTestControlCore>b__9(Object obj)
   at DevExpress.ExpressApp.EasyTest.WebAdapter.WebCommandAdapter.ExecuteTimeoutFunction(Int32 timeoutMilliseconds, Int32 sleepTime, Predicate`1 predicate, Func`1 onTimeoutPredicate)
   at DevExpress.ExpressApp.EasyTest.WebAdapter.WebCommandAdapter.GetIReflectTestControlCore(String testControlsName, IHTMLDocument2 doc)
   at DevExpress.ExpressApp.EasyTest.WebAdapter.WebCommandAdapter.GetIReflectTestControl(String testControlsName, IHTMLDocument2 doc)
   at DevExpress.ExpressApp.EasyTest.WebAdapter.WebCommandAdapter.UpdateTestControls()
   at DevExpress.ExpressApp.EasyTest.WebAdapter.WebCommandAdapter.WaitForBrowserResponse(Boolean waitPostback, Boolean isSecondCall)
   at DevExpress.ExpressApp.EasyTest.WebAdapter.WebAdapter.CreateCommandAdapter()
   at DevExpress.EasyTest.Framework.TestExecutor.CreateCommandAdapterCore(IApplicationAdapter adapter)
   at DevExpress.EasyTest.Framework.TestExecutor.ExecuteCommands(IApplicationAdapter adapter, String& applicationName)
    InnerException is null

After several hours of researching and googling, we found out the Installation of KB3025390 breaks out-of-process JavaScript execution in IE11 ticket on MS Connect
as well as possible workarounds at https://code.google.com/p/selenium/issues/detail?id=8302