App Development topics

.NET

Thinuka99 — Fri, 13 Mar 2026 17:39:22 GMT

Hi everyone! 👋

I’m new to this community and currently learning .NET App Development. I’m really excited to join and connect with developers here.

I believe the discussions and knowledge shared in this community are very valuable, especially for beginners like me. I’m looking forward to learning from your experiences and improving my development skills.

If you have any tips, recommended resources, or advice for someone starting with .NET, I would really appreciate it.

Happy to be part of this community! 😊

Using WinUI 3 without XAML

tommerfrancis — Fri, 16 Jan 2026 07:37:38 GMT

Hello everyone, I would like to know that how to use WinUI 3 without XAML. Thank you very much.

Windows Forms user control layout issues at runtime

tjmitchem — Wed, 31 Dec 2025 15:01:45 GMT

I'm hoping the good folls of this community can help me figure out what's going on with a Windows Forms user control that I created and am trying to use.

I created a user control that represents a single band of a parametric equalizer. In the designer, the control looks like this:

When I debug the control in the Test Container, things look good:

If we take a look at the actual PEQ application that will use the control, things still look OK in the designer:

It's only when I fire up the application that things go... awry:

What happened to all the TextBoxes? And the ComboBoxes? I''ve got a feeling that the fix for this is something really simple, and I'm going to feel like a complete idiot for not figuring out the obvious.

Can anyone tell me what my dumb self did wrong?

WPF application becomes unresponsive after plugging/ unplugging USB device supporting pen events

shepburn — Tue, 07 Oct 2025 18:38:42 GMT

I've run across an issue on Windows 10 and 11 where WPF apps seem to become unresponsive when unplugging or plugging in a USB device that registers as an input device that can receive touch/stylus events. This can be seen by creating a basic WPF app in Visual Studio, running it, and then adding/removing one of these devices.

I used Spy++ to see which messages the app was receiving. I saw a number of messages I was expecting to see - WM_DEVICECHANGE, WM_POINTERDEVICECHANGE, as well as 0x02C8 or 0x02C9 (WM_TABLET_ADDED or WM_TABLET_DELETED, respectively). However, after this, thousands (or sometimes tens of thousands) of messages were sent to a window belonging to the app that is at (0,0) with dimensions 0x0. Its caption is "OLEChannelWnd". The messages are mostly the same:

They're all posted to the window
The message ID is 0x0400 (WM_USER + 0)
The wParam is always the same (0x0000BABE)
The lParam varies each time I restart the WPF app, but they seem to settle on a small number of values - for example, the last time I tried this, I saw 0x05D08BB0 4-6 times, then 0x0D1B8E98 a dozen or more times, then 0x0D1B7B90 several times, and so on.

During these messages, the app would become unresponsive for as long as these messages were posted. This could take upwards of 5- 10 minutes before recovering, and sometimes would result in a crash from the app running out of memory.

After doing research online, I found some posts that talked about a possible issue in the PenThreadWorker thread - that it could be running into some kind of deadlock when initializing certain objects. I also found several posts that mentioned disabling the stylus & touch events by setting "Switch.System.Windows.Input.Stylus.DisableStylusAndTouchSupport". I can add this to the app.config for my app as follows:

or, equivalently, I can do the following during application startup:

AppContext.SetSwitch("Switch.System.Windows.Input.Stylus.DisableStylusAndTouchSupport", true);

This does fix the issue - I don't see these WM_USER messages being sent to the app, and as such the app becomes immediately responsive once the device is plugged/unplugged. However, one of the WPF apps that I'm working with (i.e. not the simple test app) needs to process tablet events, so this setting can't be used there. Furthermore, it can only be set either in app.config or during application startup - any calls to it after that are ignored.

I've tried this with .NET 4.5.1, .NET 4.6 (which is required to use the code-based method) as well as .NET 4.8.1, but in all cases I see this same result.

As mentioned, I know this isn't an issue unique to my app since I'm able to reproduce this issue by creating a basic WPF app and following the same steps. Additionally, I observed the same issue with other test applications I've found online while trying to troubleshoot this issue. Interestingly, I have observed this within Microsoft's own Visual Studios 2017 (which is what I'm using for development) and have found a few other threads online from other people running into the same problem with their apps. I have also tried updating to later Visual Studios versions for development of my app, but this doesn't solve the issue either.

Finally, I followed this post from Microsoft regarding Disabling RealTimeStylus for WPF Apps and still was unable to fix the issue.

MAUI Android API 35: Action Bar still visible despite NavBarIsVisible=False

manjit — Fri, 22 Aug 2025 07:35:51 GMT

Before API 35 it was ok. I am using .NET 9, Android API 35, using Shell, etc.

I have tried: Shell.NavBarIsVisible, NavigationPage.HasNavigationBar, theme tweaks, etc.
What’s still happening: Title bar remains visible on Android.

Is clean architecture overkill for small teams maintaining a single web app ?

JohnDobbins — Thu, 07 Aug 2025 12:36:44 GMT

I've been exploring clean architecture and while I appreciate its separation of concerns and testability, I can't help but wonder, it is over for small teams ( say 2-4 devs) maintaining a single, relatively stable web application ?

Implementing clean architecture means more layers, more interfaces, and potenitally more ceremony, which might slow things down, especially if the team is trying to move quickly or lacks deep experience with the pattern.

At the same time, I get the value of long-term maintainability and scalability, even for small projects that could grow. What pain points or benefits did you encounter ? Did it help or hinder onboarding, testing or refactoring ?

Is it normal for CollectionView to lag on larger lists, or am I missing an optimizaiton ?

Bonilla — Thu, 07 Aug 2025 12:12:29 GMT

I've been working with .NET MAUI recently and have run into some performance concerns when using CollectionView. Specifically, when binding a large dataset ( let's say 500+ items), the scrolling becomes noticeably sluggish, especially on Android

I've tried a few basic optimizations, like setting CachingStrategy = "RecycleElement" and minimizing the complexity of the DataTemplate, but the lag persists . I'm not using images or heavy UI elements either, it's just a simple text-based item template.

is this kind of lag expected with MAUI's CollectionView or is there a known workaround ? Are there additional performance tuning steps I should try ( virtualization tricks, async loading, grouping) ?

WPF App on Windows Server (RDP) – Error Sometimes When Opening New Window

3ColorCat — Mon, 04 Aug 2025 17:20:14 GMT

Hi everyone,

I have a WPF app that runs from a network drive. It works fine on Windows 11 at the office. But when users run it through Remote Desktop on a Windows Server 2019 virtual machine (using the exact same .exe from the same network drive location), some of them get an error when opening a new window.

The app starts normally, but the error happens only when opening another window — and not for every user.

Strangely, the next day the same user can open the app and use it normally again without changing anything.

Has anyone seen this before or know how to fix it?

I’ve also attached:

A screenshot of the error message

The function that causes the error

Thanks a lot!

How to decouple views from view models using CommunityToolKit.mvvm

CSharpDev — Sat, 12 Jul 2025 17:03:00 GMT

I am writing my first MVVM app using CommunityTookit.mvvm. I am using as reference the Micrsoft Learning link here. This link shows the setting of the viewmodel to the view DataContext using the following statement in the view's .cs file:

this.DataContext = App.Current.Services.GetService<ContactsViewModel>();

The problem with this as I see it is that this statement couples the view to the view model, in this case ContactsViewModel. This means that in another app the view cannot be used with another viewmodel without modifying the view, i.e. changing ContactsViewModel above to another viewmodel type. This means that the view cannot be stored in a common library that is shared among different apps.

There is a C# Corner example with the older MVVM TookKit that solved this problem using a ViewModelLocator class. This project is found here. The solution is to put the following code in the view's XAML file:

DataContext="{Binding Main, Source={StaticResource Locator}}"

The source object for the binding is found by looking for a ResourceDictionary that is in the scope of the view and which has an entry whose key is "Locator". In app.xaml which by definition is always in scope we have:

<Application.Resources>
<ResourceDictionary>
<vm:ViewModelLocator x:Key="Locator" d:IsDataSource="True" />
</ResourceDictionary>
</Application.Resources>

The Dictionary element with key "Locator" is an object of type ViewModelLocator. In the ViewModelLocator class there is a Main property that always returns an instance of MainViewModel:

public MainViewModel Main
{
get
{
return ServiceLocator.Current.GetInstance<MainViewModel>();
}
}

In our example, the view's DataContext binds to the Main property of the ViewModelLocator object. The value of the Main property is a MainViewModel object and this becomes the DataContext of the view.

We can now in a different app re-use the view without changing it. All we have to do in the next app is to create a different ViewModelLocator object that specifies a different viewmodel in its Main property. The view is now completely decoupled from the view model.

My question is, how would we de-couple the view from the view model using the CommunityToolkit.Mvvm? Do we also use a ViewModelLocator class? Is there a more elegant way with dependency injection?

Another question I have is, suppose we want to use in one app the same view twice with different view models. An example of where we might want to do this is if we had a view that displayed a chart. It is conceivable that we might want to have more than one view model display its data using the same chart view. I cannot see how to do this in either of the above Microsoft or C# Corner examples.

Deeply Disappointed with Copilot+

inda — Fri, 04 Jul 2025 18:46:37 GMT

At the company where I work, we purchased a Copilot+ laptop with the hope of being able to use the new Windows AI libraries, such as Windows.AI.TextRecognition. The library works well, but we are unable to process more than 2 documents concurrently, which severely limits our document processing capacity.
We also feel misled, as we did not see any mention anywhere of such a limitation regarding the library. I would appreciate it if a Microsoft representative could confirm whether this limitation exists and, if not, let us know if there is any way to increase this limit.
Thank you in advance.

Supercharging Solution Architecture with GitHub Copilot Prompts Every Architect Should Know

JohnNaguib — Tue, 24 Jun 2025 09:16:17 GMT

As a Solution Architect, you’re often juggling high-level system design, reviewing code, drafting technical documentation, and ensuring that your solutions meet both business and technical requirements. GitHub Copilot, powered by advanced AI, isn’t just for developers—it can be a powerful assistant for Solution Architects too.

In this blog, we’ll explore how you can craft GitHub Copilot prompts to accelerate your architectural workflow, design decisions, and documentation.

https://dellenny.com/supercharging-solution-architecture-with-github-copilot-prompts-every-architect-should-know/

Copilot Chatmicrosoft 365 copilotTag

Error when trying to test Maui iOS app using a simulator from a Mac

birneyr — Wed, 18 Jun 2025 11:55:42 GMT

I am using VS2022 on a PC and have a Maui app that i want to test the iOS version on a simulator (Mac is running Sequoia). However every time i try to run it it gives me the following error:

MessagingRemoteException: An error occurred on client Build1808319 while executing a reply for topic xvs/build/18.0.8319/execute-task/App.iOS/cebe602002fUnpackLibraryResources
NotImplementedException: The method or operation is not implemented.

Both PC and Mac are running .NET 8.0.411 and are running Maui 18.0.8319/8.0.100 from the SDK 8.0.400

Is anyone having similar issues, is it a bug in the maui-iOS component or, does anyone know the answer to this?

WinUI3 and Win11 Kiosk mode

Alex_is_programming — Tue, 10 Jun 2025 14:01:22 GMT

Hi, I have build a program in C#/WinUi3 to use in Kiosk mode on a Windows 11 machine. The program run fine in either admin or the user to be use for Kiosk mode, but once I have set AssignedAccess to the program for the Kiosk user, when I log using that user I get something that seems like the program starting (waiting cursor and all) but a blank screen with a cursor that I can see, if I click I get a ding sound from Windows and I can Ctrl-Alt-Del to get back to the admin user.
Been trying a whole lot of things, but I can't figure out how to debug this one. Anyone with similar experience?

Error on Publishing ios app (pc->imac)

BryceBurrows — Thu, 05 Jun 2025 22:31:40 GMT

Hi there, i have my PC connected to my imac. The imac builds and runs and supplies the simulator correctly so it's great from that point of view.

When i try and have the imac build the IPA file from the PC - i get the above error.
has anyone any thoughts on the solution might be?

Microsoft Store Service APIs v9.0 publisherQuery - Uniquely identifying user subscription

ttroyer — Tue, 29 Apr 2025 01:15:58 GMT

I'm working on a WPF app that will be published to the Windows Store. It supports an add-on monthly subscription. That subscription comes with consumable credits for using my app. Per user, per month, I want to track the user's credit balance.

I'm using the following Microsoft Store Service API endpoint to get the user's subscription details from my backend service:

collections.mp.microsoft.com/v9.0/collections/publisherQuery

Here's an example response (with identifying information replaced with fake data):

{ "ContinuationToken": null, "Items": [ { "RecurrenceId": null, "AcquiredDate": "2025-04-28T20:34:54.2761169+00:00", "AcquisitionType": "Recurring", "EndDate": "2025-05-31T00:00:00+00:00", "Id": "11111111111122222222222333333333", "ModifiedDate": "2025-04-28T20:34:54.277868+00:00", "ProductId": "AAAAAAAAAAAA", "ProductKind": "Durable", "Quantity": 1, "SatisfiedByProductIds": [], "SkuId": "0020", "StartDate": "2025-04-28T00:00:00+00:00", "Status": "Active", "Tags": [], "TransactionId": "11111111-1111-1111-1111-111111111111", "TrialData": { "IsInTrialPeriod": false, "IsTrial": false, "TrialTimeRemaining": "00:00:00" } } ] }

Based on this response, I can see there's an active subscription, with the start and end date. I'm trying to determine whether anything in this response uniquely represents this user's subscription for this month, and could be used as my own identifier when tracking user credit consumption.

It looks like Id and TransactionId are the only two potential candidates, but I don't know for certain that I can count on either of these for this scenario. Can anyone confirm? Is there some altogether better approach I should be using?

MYSYS2 Installation Guide for Cross-Compilation on Visual Studio 2017, 2019, 2022, and WSL2

Mousefluff — Thu, 03 Apr 2025 12:52:53 GMT

Use Notepad to create this file on your desktop or another folder: MYSYS2.txt

MYSYS2 Paths:

Use Notepad to create this file on your desktop or another folder: MYSYS2_Path_Win.txt

NOTE: This folder layout, which can be easily edited, was generated with a batch file that utilizes the default configuration that comes with the UI-based setup program / installer.

Use Notepad to create this file on your desktop or another folder: Generate_MYSYS2_Folder_Paths_Win.bat

Maui How to upload a file to web API in .NET 9

VictorCueto3 — Mon, 24 Feb 2025 22:41:10 GMT

Hi, everyone

I'm trying to upload an image to an API from a maui project.

But when I send the file, the response is always BadRequest. However the API works if I use Postman.

I create a client in a console project and it worked. So I don't know why the same code in .NET MAUI it doesn't work.

Problem is not in URI or something.

I hope you could help me.

Reegrets.

Victor Cueto

API throws the next exception:
Microsoft.AspNetCore.Http.BadHttpRequestException: Required parameter "IFormFile image" was not provided from form file.
at lambda_method3(Closure, Object, HttpContext, Object)
at Microsoft.AspNetCore.Http.RequestDelegateFactory.<>c__DisplayClass103_2.<<HandleRequestBodyAndCompileRequestDelegateForForm>b__2>d.MoveNext()
--- End of stack trace from previous location ---
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

code

Minimal API:

error:

Grid personalizado

JorgeSalas — Sat, 01 Feb 2025 22:31:10 GMT

Buenas tardes comunidad, Han trabajado con éste tipo de controles con .Net C# en Windows Forms?

Por favor me podrian indicar como lo realizaron?, gracias.

Graph API getAsync() in C#

MustangProgrammer — Thu, 30 Jan 2025 20:59:28 GMT

This is cross posted in Azure as well.

If I use graph in a console application I get the information that I request. Such as

test = await graphClient.Users.GetAsync();

If I try this in a WebMethod in the code behind of a page or in an .asmx, it never returns with the data. I know this has been mentioned before in many forums, but I did not have issues in V1.0 of the SDK. When I try to use V5+ I can't seem to get the information back. Any ideas on overcoming the issue?

Any help would be great.

Console App To Write Data To CSV

marksmanAK-2024 — Thu, 26 Dec 2024 20:00:19 GMT

I am trying to write a pre-defined list of headers to row 1, and List<string> results starting in row 2...my issue is that I get my pre-defined headers written as well as the headers from my List<string> ```cs
void WriteResultsToCSV(List<VwExport> records, string fileName)
{
DateTime currentDate = DateTime.Now;
string formattedDate = currentDate.ToString("MM-dd-yyyy");

var filePath = "/Users/owner/Downloads/" + fileName + formattedDate + ".csv";

// Define the headers
var headers = new[]
{
"Job Num",
"IM barcode Child",
"IM barcode Parent",
"ZYL_Presort",
"Full Name"
};

using (var writer = new StreamWriter(filePath, false, Encoding.UTF8))
using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
{
foreach (var header in headers)
{
csv.WriteField(header);
}
csv.NextRecord();

var trimmedRecords = records.Select(record => new
{
JobNum = record.JobNum,
IMBarcodeDigits = record.ImBarcodeDigits,
IMBarcodeCharacters = record.ImBarcodeCharacters,
OELPresort = record.OelPresort,
FullName = record.FullName
}).ToList();

csv.WriteRecords(trimmedRecords);
}

}```