Open app from another app

Question

Open app from another app

StewartBW 1,905

Hi experts

Working on 2 separate WinForms apps (.NET Framework 4.8 with VB) and going to msix bundle them to store.

Once they both are installed how can I run one of them from within the other one?

They are not associated with any file type, just need to open one of them.

How that can be done in .Net 4.8 WinForms app when running under store?

I already created the msix installer to test locally on my machine and both products are installed and working, I've seen this online:

Dim aumId = "Acme.BlahApp_5wekyb3d8bbwe!App"

Await Launcher.LaunchUriAsync(New Uri("shell:appsFolder{aumId}"))

But not sure how to get the other app's aumId, is this aumId the same for each app across all its versions? Seems the app version is included in it.

And it won't run in WinForms .NET 4.8 :(

Thanks in advance.

Anonymous

2025-07-11T05:20:49.6833333+00:00
Thank you for reaching out. Please find the answer below You're absolutely right that Launcher.LaunchUriAsync won’t work in .NET Framework 4.8 WinForms apps because it’s a UWP API that depends on Windows Runtime (WinRT), which isn’t supported in that environment. Instead, the best approach is to use Protocol Activation, which is fully compatible with .NET Framework and MSIX packaging.

To implement this, define a custom URI scheme (like myapp://) in the second app’s MSIX manifest. You do this by adding a <Protocol> extension inside the <Extensions> node of the manifest:
StewartBW 1,905 Reputation points

2025-07-15T12:29:55.01+00:00

Thanks @RLWA32 , it works just fine, but I can't replace "Microsoft.WindowsCalculator_8wekyb3d8bbwe!App" with my app name which is already installed / side-loaded:

This app does not support the contract specified or is not installed. (Exception from HRESULT: 0x80270254)

Does it work for side-loaded apps? Because it's installed and working!

What is the app does not support the contract? How to make it support :(

Thanks :)
RLWA32 52,571 Reputation points

2025-07-15T13:35:45.6233333+00:00

The example that I posted uses Calculator's AppUserModelId to run the app. If your application has an AppUserModelId then that is what should be used in the example code.
StewartBW 1,905 Reputation points

2025-07-16T13:40:13.8833333+00:00

oops, sorry my bad, I used full package name instead of AUMID, it's just great, please convert to answer :)
RLWA32 52,571 Reputation points

2025-07-16T14:00:36.0833333+00:00

Glad to see that it works for you. Comment converted.
soren vail 0 Reputation points

2025-07-19T11:29:31.5733333+00:00

To open one MSIX WinForms app from another, find the other app’s AUMID in its manifest. Since WinForms can’t use UWP launch methods, use a custom URI scheme set in the second app and launch that URI to start it.

Answer accepted by question author

RLWA32 52,571

For what its worth, I was playing around a while ago with launching a store app from a desktop process. Following minimal example will launch Calculator from a .Net Framework 4.8 desktop console application. I don't know if this is applicable in any way to your circumstance.

Module Module1

    Public Enum ActivateOptions
        None = &H0
        DesignMode = &H1
        NoErrorUI = &H2
        NoSplashScreen = &H4
    End Enum
    <ComImport, Guid("2e941141-7f97-4756-ba1d-9decde894a3d"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)>
    Public Interface IApplicationActivationManager
        Function ActivateApplication(appUserModelId As String, arguments As String, options As ActivateOptions, ByRef processId As UInt32) As Integer
        Function ActivateForFile(appUserModelId As String, itemArray As IntPtr, verb As String, ByRef processId As UInt32) As Integer
        Function ActivateForProtocol(appUserModelId As String, itemArray As IntPtr, ByRef processId As UInt32) As Integer
    End Interface

    Sub Main()
        Dim clsidActivationManager = New Guid("45BA127D-10A8-46EA-8AB7-56EA9078943C")
        Dim ta = Type.GetTypeFromCLSID(clsidActivationManager)
        Dim iAppMgr As IApplicationActivationManager = Activator.CreateInstance(ta)
        Dim pid As UInt32 = 0
        iAppMgr.ActivateApplication("Microsoft.WindowsCalculator_8wekyb3d8bbwe!App", "", ActivateOptions.None, pid)
        Console.WriteLine($"Calculator pid is {pid}")

    End Sub

End Module

RLWA32 52,571 Reputation points

2025-07-19T08:52:48.8033333+00:00

@StewartBW Did you forget that you asked me to convert a previous comment to this Answer? :)
StewartBW 1,905 Reputation points

2025-07-19T12:48:56.62+00:00

oops so sorry bro, indeed your solution was a life saver :)

StewartBW 1,905

Hello

Sorry to reply to a closed thread, but do you have any idea how to use ActivateForProtocol based on your code?

    Private Enum ActivateOptions
        None = &H0
        DesignMode = &H1
        NoErrorUI = &H2
        NoSplashScreen = &H4
    End Enum
    <ComImport, Guid("2e941141-7f97-4756-ba1d-9decde894a3d"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)>
    Private Interface IApplicationActivationManager
        Function ActivateApplication(appUserModelId As String, arguments As String, options As ActivateOptions, ByRef processId As UInt32) As Integer
        Function ActivateForFile(appUserModelId As String, itemArray As IntPtr, verb As String, ByRef processId As UInt32) As Integer
        Function ActivateForProtocol(appUserModelId As String, itemArray As IntPtr, ByRef processId As UInt32) As Integer
    End Interface
    Friend Sub DefaultBrowser(ByVal InputURL As String)
        Dim CLSIDActivationManager = New Guid("45BA127D-10A8-46EA-8AB7-56EA9078943C")
        Dim MyTypeCLSID As Type = Type.GetTypeFromCLSID(CLSIDActivationManager)
        Dim IAppManager As IApplicationActivationManager = CType(Activator.CreateInstance(MyTypeCLSID), IApplicationActivationManager)
        Dim MyProcessID As UInt32 = 0
        ' We can use the "appUserModelId" for opening URLs, but we are leaving this empty so Windows will figure out which app to use for the protocol.
        Dim result As Integer = IAppManager.ActivateForProtocol(InputURL, Nothing, MyProcessID)
    End Sub

It throws exception: The remote procedure call failed. (Exception from HRESULT: 0x800706BE)

However, it opens the default browser, but not with the specified URL, it always opens:

http://www.msftconnecttest.com/redirect

Any idea how to get it work to open the given URL without exception?

Thanks indeed :)

RLWA32 52,571 Reputation points

2025-08-15T09:47:54.1466667+00:00

The documentation at IApplicationActivationManager::ActivateForProtocol indicates that the second parameter should be an IShellItemArray that contains a single item.

The second parameter used in the declaration was just a placeholder and wasn't relevant for the sample code's purpose of calling ActivateApplication.

I was able to get ActivateForFile to work (C# test) with the Paint3d app and a .png image in the file system.

But haven't played with ActivteForProtocol.

1 additional answer

Your answer

Anonymous

2025-07-11T05:20:49.6833333+00:00

Thank you for reaching out. Please find the answer below You're absolutely right that Launcher.LaunchUriAsync won’t work in .NET Framework 4.8 WinForms apps because it’s a UWP API that depends on Windows Runtime (WinRT), which isn’t supported in that environment. Instead, the best approach is to use Protocol Activation, which is fully compatible with .NET Framework and MSIX packaging.

To implement this, define a custom URI scheme (like myapp://) in the second app’s MSIX manifest. You do this by adding a <Protocol> extension inside the <Extensions> node of the manifest:
StewartBW 1,905 Reputation points

2025-07-15T12:29:55.01+00:00

Thanks @RLWA32 , it works just fine, but I can't replace "Microsoft.WindowsCalculator_8wekyb3d8bbwe!App" with my app name which is already installed / side-loaded:

This app does not support the contract specified or is not installed. (Exception from HRESULT: 0x80270254)

Does it work for side-loaded apps? Because it's installed and working!

What is the app does not support the contract? How to make it support :(

Thanks :)
RLWA32 52,571 Reputation points

2025-07-15T13:35:45.6233333+00:00

The example that I posted uses Calculator's AppUserModelId to run the app. If your application has an AppUserModelId then that is what should be used in the example code.
StewartBW 1,905 Reputation points

2025-07-16T13:40:13.8833333+00:00

oops, sorry my bad, I used full package name instead of AUMID, it's just great, please convert to answer :)
RLWA32 52,571 Reputation points

2025-07-16T14:00:36.0833333+00:00

Glad to see that it works for you. Comment converted.
soren vail 0 Reputation points

2025-07-19T11:29:31.5733333+00:00

To open one MSIX WinForms app from another, find the other app’s AUMID in its manifest. Since WinForms can’t use UWP launch methods, use a custom URI scheme set in the second app and launch that URI to start it.
RLWA32 52,571 Reputation points

2025-07-19T08:52:48.8033333+00:00

@StewartBW Did you forget that you asked me to convert a previous comment to this Answer? :)
StewartBW 1,905 Reputation points

2025-07-19T12:48:56.62+00:00

oops so sorry bro, indeed your solution was a life saver :)
StewartBW 1,905 Reputation points

2025-08-14T20:12:06.7866667+00:00

Hello

Sorry to reply to a closed thread, but do you have any idea how to use ActivateForProtocol based on your code?

Private Enum ActivateOptions None = &H0 DesignMode = &H1 NoErrorUI = &H2 NoSplashScreen = &H4 End Enum <ComImport, Guid("2e941141-7f97-4756-ba1d-9decde894a3d"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> Private Interface IApplicationActivationManager Function ActivateApplication(appUserModelId As String, arguments As String, options As ActivateOptions, ByRef processId As UInt32) As Integer Function ActivateForFile(appUserModelId As String, itemArray As IntPtr, verb As String, ByRef processId As UInt32) As Integer Function ActivateForProtocol(appUserModelId As String, itemArray As IntPtr, ByRef processId As UInt32) As Integer End Interface Friend Sub DefaultBrowser(ByVal InputURL As String) Dim CLSIDActivationManager = New Guid("45BA127D-10A8-46EA-8AB7-56EA9078943C") Dim MyTypeCLSID As Type = Type.GetTypeFromCLSID(CLSIDActivationManager) Dim IAppManager As IApplicationActivationManager = CType(Activator.CreateInstance(MyTypeCLSID), IApplicationActivationManager) Dim MyProcessID As UInt32 = 0 ' We can use the "appUserModelId" for opening URLs, but we are leaving this empty so Windows will figure out which app to use for the protocol. Dim result As Integer = IAppManager.ActivateForProtocol(InputURL, Nothing, MyProcessID) End Sub

It throws exception: The remote procedure call failed. (Exception from HRESULT: 0x800706BE)

However, it opens the default browser, but not with the specified URL, it always opens:

http://www.msftconnecttest.com/redirect

Any idea how to get it work to open the given URL without exception?

Thanks indeed :)
RLWA32 52,571 Reputation points

2025-08-15T09:47:54.1466667+00:00

The documentation at IApplicationActivationManager::ActivateForProtocol indicates that the second parameter should be an IShellItemArray that contains a single item.

The second parameter used in the declaration was just a placeholder and wasn't relevant for the sample code's purpose of calling ActivateApplication.

I was able to get ActivateForFile to work (C# test) with the Paint3d app and a .png image in the file system.

But haven't played with ActivteForProtocol.

Answer 1

StewartBW 1,905

@Anonymous

Thanks but your code is blank! :)

0 comments

Share via

Open app from another app

1 additional answer

Your answer