VSIX Extension Which Provides Setting Overrides During Debugging of Target Application

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VSIX Extension Which Provides Setting Overrides During Debugging of Target Application

Dominick Marciano (MSC Technology North America) 0

I am attempting to create a VSIX extension which allow app settings to be overridden while the target application is being debugged (similar to User Secrets), however nothing I have tried has worked and feel that I must be missing something basic. My goal is for the extension to be able to provide overrides for configuration values without having anything permanent written to the file system. However, every example I have found either doesn't work or doesn't meet my goals. At a minimum I would like this to work for ASP.NET Core applications (.NET6+) and (if possible) console applications, but at the moment I am focusing only on the ASP.NET projects.

I was able to create the extension and have it run when the target application is executed, but it never gets the new values. I tried implementing the suggestions provided under How to write a Visual Studio extension that injects environment variables into a .NET 4.8 application on debug launch but neither suggestion worked. For Option A, implement a launch settings provider, I was unable to find how to bring in IVsDebugLaunchSettingsProvider to the VSIX project. This interface was not available in any assemblies I added. There as a similar interface I saw a recommendation from, ILaunchSettingsProvider, but again I was not able to find any way to inherit this interface.

For Option B, I also couldn't find out how to just add environment variables to the config. Various suggestions I saw suggested retrieving Environment or EnvironmentVariables from the properties, but neither of these existed in the target application while it was debugging.

I was only able to find two ways that worked. First, I was able to find is to write the values to the launchSettings.json file, however this has two issues. For console applications, this file doesn't necessarily exist. Even restricting to ASP.NET applications, this file is still under source control and the changes the extension makes should only be available during the debugging session; there should be no risk of the changes being committed to the repository.

The second was by using Environment.SetEnvironmentVariable("MaintenanceConfiguration__MaintenanceWindowCheckEnabled", "False", EnvironmentVariableTarget.User); but that adds it permanently and then would have to worry about cleaning that up when the debugging is completed. I did try using EnvironmentVariableTarget.Process at first, but that didn't work I am assuming because the extension is running in its own process.

The other issue I see with using the environment variables in this way is that some of our solutions have multiple projects that are ran together. They may potentially have the same settings structure, e.g. MaintenanceConfiguration__MaintenanceWindowCheckEnabled, however one may need this to be true and the other false and by having a single environment variable, it will force them to be the same.

What I am looking for is how can I implement a extension that does the following:

When target application is started, the extension can override one or more app setting values (or add if necessary)
The updated values are immediately available using IConfiguration in the target application
No changes to the file system that could potentially get checked into source control

Is what I am attempting to do even possible? Any help or guidance would be greatly appreciated as I have been working on this for two days without any real progress. TIA.

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Answer 1

Adiba Khan 2,345 Microsoft External Staff

Thank you for detailed explanation. This is well thought out scenario and you are not missing anything obvious. What you are trying to achieve (runtime-only configuration overrides during debugging, without touching disk or persisting state) is not directly supported by current Visual Studio extensibility model, which is why the approaches you tried are hitting limitations.

That said, here's the most accurate and recommended approach, along with clarification on why the previous attempts didn't work.

Key Limitation

A VSIX extension runs in a separate process(devenv.exe) and does not have direct control over the configuration pipeline of the debugged process (your ASP.NET Core app).

This means:

EnvironmentVariableTarget.Process -> applies to VS process, not target app.
User/Machine-> persists (not desired)
launchSettings.json-> file-based ( not desired).

Recommended Approach (Supported and clean)

Use Debug Launch Customizable via DebugLaunchProvider

Instead of trying modify config after launch, you should inject environment variables at debug launch time using:

IDebugProfileLaunchTargetsProvider (modern approach)

This is the correct extensibility point for .NET Core / ASP.NET Core projects.

What this gives you:

Runtime-only overrides
No file system changes
Scoped to debug session
Works with ASP.NET Core config system (IConfiguration)

Implementation Outline

Create a VSIX extension

Export a custom launch provider:

   [Export(typeof(IDebugProfileLaunchTargetProvider))]
   [AppliesTo(ProjectCapability.DotNetCore)]
   public class CustomLaunchProvider : IDebugProfileLaunchTargetsProvider
   {
   	public Task<IReadOnlyList<IDebugLaunchSettings>> QueryDebugTargetsAsync(
   		DebugLaunchOptions launchOptions,
   		ILaunchProfile profile)
   	{
   		var settings = new DebugLaunchSettings(launchOptions)
   		{
   			LaunchOperations = DebugLaunchOperation.CreateProcess,
   			Executable = profile.ExecutablePath,
   			Arguments = profile.CommandLineArgs,
   			CurrentDirectory = profile.WorkingDirectory
   		};
   
   		//Inject environment variable here
   		settings.Environment["MaintenanceConfiguration__MaintenanceWindowCheckEnabled'] = "false";
   		
   		return Task.FromResult<IReadOnlyList<IDebugLauncgSettings>>(
   			new[] {settings});
   	}
   }

Important notes

Use __(double underscore) for nested config keys in ASP.NET Core.
These values will be picked up automatically via: IConfiguration["MaintenanceConfiguration__MaintenanceWindowCheckEnabled'] = "false";
This only applies during debugging, exactly matching your requirement

Alternative (if you need more control)

if you need even more flexibility (e.g., per-project overrides in multi-project solutions):

Implement a custom configuration provider in your app.
Read values from a temporary in-memory source (e.g., named pipe, local service, etc.)

But this require app-level changes, whereas the above VSIX approach does not.

Please try the steps shared above and let me know if this resolves the issue.

If it works, you may mark this reply as the Accepted Answer — this helps other customers with similar questions find the solution faster.

Dominick Marciano (MSC Technology North America) 0 Reputation points

2026-04-22T13:39:43.26+00:00

Thank you for this detailed response and the full example is greatly appreciated. I will attempt to implement the suggestion you provided today/tomorrow and confirm if this does indeed work for my extension.
Adiba Khan 2,345 Reputation points Microsoft External Staff

2026-04-24T09:27:04.72+00:00

"Hope you’re doing well. We’re following up on this thread to check if the issue is still occurring or has been resolved. If it has been resolved, kindly mark the answer as accepted by clicking the "Yes I agree" button post thread closure for better visibility to community members."
Dominick Marciano (MSC Technology North America) 0 Reputation points

2026-04-24T11:34:54.1733333+00:00

Sorry, I have not had a chance to try it yet unfortunately as I have been having some system issues the past 2 days (profile memory issues preventing me from building any code), but I have not forgotten about it. Thank you.
Dominick Marciano (MSC Technology North America) 0 Reputation points

2026-04-27T12:53:12.64+00:00
I attempted to implement this but several of the references can't be found. Specifically, IDebugProfileLaunchTargetProvider, ILaunchProfile, IDebugLaunchSettings, DebugLaunchSettings, and ProjectCapability.DotNetCore`.

I have the following namespaces imported:

using System.Composition; using Microsoft.VisualStudio.ProjectSystem; using Microsoft.VisualStudio.ProjectSystem.Debug; using Microsoft.VisualStudio.Shell;

however the Microsoft.VisualStudio.Shell namespace is grayed out as it is not currently be used by any of the objects in the class. I did check what NuGet's I have installed and I ensure the following were added:

Microsoft.VisualStudio.Shell.Framework

Microsoft.VisualStudio.Shell.15.0

Microsoft.VisualStudio.ProjectSystem

I tried searching online for more information about IDebugProfileLaunchTargetsProvider, but wasn't able to find anything. Is there some other NuGet(s) I need to add to be able to implement the example you provided?

I tried asking Copilot and it says I need version 17.10.46 or later of Microsoft.VisualStudio.ProjectSystem.Sdk, but the latest version on NuGet.org is 17.9.380, which I do have installed. I also attempted (again, based on a Copilot suggestion), adding a direct assembly reference to Microsoft.VisualStudio.ProjectSystem.dll and Microsoft.VisualStudio.ProjectSystem.VS.dll` (located in C:\Program Files\Microsoft Visual Studio\18\Insiders\Common7\IDE\CommonExtensions\Microsoft\Project), however that did not resolve the issue either.

Could all of these issues have to do with the fact that the VSIX project is .NET 4.7.2 (which is the version that was automatically set when using the VSIX template)?

Thank You
Dominick Marciano (MSC Technology North America) 0 Reputation points

2026-04-27T16:48:12.61+00:00

I continued to look into this and I found that if I download the GitHub repostiory https://github.com/dotnet/project-systemand I add a reference to both Microsoft.VisualStudio.ProjectSystem.Managed.dll & Microsoft.VisualStudio.ProjectSystem.Managed.VS.dll located in the \artifacts\Debug\bin\Dlls\net472 folder, then I can bring in the interfaces provides in the sample code, however I am still unable to get it to work.

I was still getting an error on [AppliesTo(ProjectCapability.CSharp)] saying that because ProjectCapability is marked as internal I cannot use it. I tried updating this to both CSharp, as well as LaunchProfiles, and the code builds fine. However, when I run the extension in debug mode, and start my target application in debug mode as well, none of the breakpoints in CustomLaunchProvider are hit.

Implementing IDebugProfileLaunchTargetsProvider also required me to add the methods OnBeforeLaunchAsync and OnAfterLaunchAsync, but neither of these methods got hit either. Is there something else that needs to be completed for the system to see this exported provider?
Adiba Khan 2,345 Reputation points Microsoft External Staff

2026-04-28T09:53:52.55+00:00
Thank you for the follow up and for sharing the additional findings-this helps clarify exactly where things are breaking down. You have actually uncovered a few important details and I will address each of your questions directly.1. Missing types (IDebugProfileLaunchTargets-Provider, etc.)

you are correct the reason these types cannot be resolved via standard NuGet packages is because these APIs are part of CPS(common project system) and are fully supported for public VSIX consumption via NuGet.

specifically:

IDebugProfileLaunchTargets-Provider

ILaunchProfile

IDebugLaunchSettings

DebugLaunchSettings these live in internal/as the get assemblies used by Visual Studio itself and are not guaranteed to be accessible or stable for VSIX extensions.

Why your GitHub work around “worked”

Referencing:

Microsoft.VisualStudio.ProjectSystem.Managed.dll

Microsoft.VisualStudio.ProjectSystem.Managed.VS.dll

from the repo builds gives you access at compile time, but: these assemblies are not the same ones loaded inside Visual Studio at runtime

so MEF composition fails silently -> your provider is never discovered-> breakpoints are never hit.

[AppliesTo(ProjectCapability.CSharp)] Issue you observed: ProjectCapabiliy is internal. That is expected. Correct approach: Use a string based capability expression, for example:
[AppliesTo("CSharp")]
OR for .net core project:
[AppliesTo("DotNetCore")]
You cannot rely on ProjectCapability.* constants in VSIX – they are not public API.

Provider not being hit (breakpoints never triggered) this is the key issue. even after resolving compilation: your MEF component is not being composed by Visual Studio root cause is missing correct MEF export context Even though you used:
[Export(typeof(IDebugProfileLaunchTargetProvider))]
Visual Studio will only load this if:

the assembly is loaded in a correct CPS context

the interface is from the same assembly identity as VS expects

because you reference locally built DLLs-> type identity mismatch occurs

Methods like OnBeforeLaunchAsync not hit: same root cause: the provider itself is never instantiated-> lifecycle methods are never called.

Dot NET Framework 4.7.2 concern you asked: could this be due to vsixtargeting.net framework 4.7.2? No this is not the issue.

VSIX extensions are expected to target.net framework (typically 4.7.3 or 4.8)

the problem is API accessibility and CPS boundaries not framework version

Important reality check

what you are attempting:

inject runtime configuration overrides into a debug target via vsix (without file/system changes)

this scenario is not fully supported by a public Visual Studio extensibility APIs today.

The API's you are trying to use:

are internal CPS extensibility points

used by Visual Studio itself

not officially supported for 3rd party VSIX extensions

supported and reliable alternatives

Option1: Use launchsettings.json (recommended baseline)

Yes, it touches disk but:

You can generate it dynamically

clean it up post debug

works reliably across all project types

Option 2: Pre-launch script/ wrapper process

instead of VSIX injection:

launch your app via a custom executable/script

Set environment variables before process start

Option 3: Application level overrides(best long term)

inside your asp.net core:

builder.Configuration.AddInMemoryCollection(new Dictionary<string, string> { ["MaintenanceConfiguration:MaintenanceWindowCheckEnabled"] = "false" });

you can control this via:

external signal(file,pipe,service)

debug only flag

fully supported

no VSIX dependency

works in all environments

Final answer to your main question

is there something else needed for the system to see this exported provider?

no, your implementation is correct in a structure

the issue is that:

the required interfaces are not publicly supported

your assembly is not being composed due to type identity mismatch

the closest supported solution is:

inject environment variables via custom launch mechanism outside vsix

handle overrides inside the application(IConfiguration)

Please try the steps shared above and let me know if this resolves the issue.

If it works, you may mark this reply as the Accepted Answer — this helps other customers with similar questions find the solution faster.
Dominick Marciano (MSC Technology North America) 0 Reputation points

2026-04-28T15:37:46.6266667+00:00

I am very confused now. In the latest comment you mentioned "the required interfaces are not publicly supported", that the closest supported solutions are either inject environment variables via custom launch mechanism outside vsix handle overrides inside the application, and that the API are not supported by 3rd party extensions.

However, the implementation I was attempting with these interfaces were directly taken from the sample you provided on April 22nd and your comments seems to indicate that this was indeed possible and the correct way. Your latest comments though seem to directly contradict that now saying that the interfaces are not available. So, can you clarify what the original sample was for, and why that was provided as a solution, if none of the interfaces that are required for it are available for use? It seems that I spent the past 2 days trying to implement a solution provided by Microsoft that was known not to be the correct way.
Adiba Khan 2,345 Reputation points Microsoft External Staff

2026-04-29T09:58:54.2533333+00:00
Thank you for your patience here and I completely understand your frustration. you are absolutely right to call this out and I want to clarify things transparently so there's no confusion going forward.

What caused the confusion?

The sample and earlier guidance I provided were based on how Visual Studio itself implements debug launch extensibility internally (CPS)

Those interfaces like:

IDebugProfileLaunchTargets-Provider

ILaunchProfile

DebugLaunchSettings

Are indeed real and used by Visual Studio which is why the sample compiles when you reference the assemblies manually

however the key detail that wasn't clear earlier is: these APIs are not part of the officially supported public VSIX extensibility service

why your implementation did not work(even though it compiled)

you did everything correctly from an implementation standpoint. The issue is:

the assemblies you referenced from the GitHub repo are not the same runtime assemblies loaded by Visual Studio

this causes a type identity mismatch in MEF composition

as a result Visual Studio does not discover or instantiate your provider

that's why breakpoints are never hit and OnBeforeLaunchAsync/OnAfterLaunchAsync are never called

So the failure is not in your code it's due to platform boundaries

why the sample was misleading

this sample demonstrates: how the mechanism works internally

but it does not imply: that it is not for 3rd party VSIX extensions

that distinction should have been made clearer earlier-apologies for the confusion and the time you spent pursuing this path.

Direct answer to your concern

more accurately it is valid internal pattern used by Visual Studio.

But it is not a supported or documented extension point for external developers

so while it looks like a solution it is not usable in reliable supported way in vsix today

what will work(supported options)

given your original requirements these are practical options

application level override(recommended) handle overrides inside your app via IConfiguration(e.g., in memory provider or conditional debug logic)

custom launch wrapper launch the app through a script/executable that sets environment variables before startup

launchSettings.json (with safeguards)

if acceptable modified temporarily and clean up post debug

your approach and investigation were technically correct. The limitation is not documented clearly which led to this confusion. There is currently no supported VSIX only way to inject runtime configuration into debug targets without persistence.
Adiba Khan 2,345 Reputation points Microsoft External Staff

2026-05-05T09:29:31.01+00:00

Hope you’re doing well. We’re following up on this thread to check if the issue is still occurring or has been resolved. If it has been resolved, kindly mark the answer as accepted by clicking the "Yes I agree" button post thread closure for better visibility to community members.
Dominick Marciano (MSC Technology North America) 0 Reputation points

2026-05-05T17:06:41.3066667+00:00
At this point, just close this thread. The information being provided is conflicting, not helpful, and just plain wrong (apparently) at points. For example, your last comment says:

"why the sample was misleading

this sample demonstrates: how the mechanism works internally

but it does not imply: that it is not for 3rd party VSIX extensions"

but your very first response said:

"Recommended Approach (Supported and clean)

Use Debug Launch Customizable via DebugLaunchProvider

Instead of trying modify config after launch, you should inject environment variables at debug launch time using:

IDebugProfileLaunchTargetsProvider (modern approach)

This is the correct extensibility point for .NET Core / ASP.NET Core projects"

There is no confusion here. First response specifically stated that this was supported, the correct way to do it, and even gave steps clearing stating to create a VSIX extension and export the launch provider

""Implementation Outline

Create a VSIX extension

Export a custom launch provider:"

but obviously this was just wrong. I am already familiar with modifying the environment variables, launch settings, etc., but as mentioned in my original post, I was explicitly trying to avoid this because of the risk.

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VSIX Extension Which Provides Setting Overrides During Debugging of Target Application

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