Smart App Control blocks WinForms / WPF sample applications from running

1. Yes, this is expected behavior when Smart App Control is enabled in enforcement (On) mode. Smart App Control blocks apps and binaries that are considered untrusted, including unknown or unsigned code. Development builds of WinForms/WPF apps typically produce unsigned executables that Smart App Control will treat as untrusted and block at runtime.

Smart App Control allows apps to run only if:

• They are recognized as safe by Microsoft’s app intelligence services, or
• They are signed with a certificate issued by a certificate authority in the Trusted Root Program.

Unsigned, unknown development builds fall outside these criteria and are therefore blocked when Smart App Control is enforcing.

2. To prevent Smart App Control from blocking development builds, use one of these supported approaches:

• Turn Smart App Control Off while doing local development:
  • Go to Settings > Privacy & Security > Windows Security > App & browser control > Smart App Control settings.
  • Set Smart App Control to Off.
  • Note: Changing from On to Off is a one-way operation via Settings; returning to Evaluation requires a reset or reinstall of Windows.
• Develop on a device or VM where Smart App Control is not enforcing:
  • Use a separate development environment (for example, a VM) where Smart App Control is left in Evaluation mode or disabled.
• Sign development builds with a trusted certificate:
  • If the binaries are code-signed with a certificate trusted by Windows (Trusted Root Program), Smart App Control will allow them to run, assuming they are not otherwise classified as unsafe.

For troubleshooting and validation:

• Use the Code Integrity event log to confirm Smart App Control is blocking the binaries:
  • Open Event Viewer > Application and Services Logs > Microsoft > Windows > CodeIntegrity > Operational.
  • Look for event ID 3077 (enforcement mode) entries showing the blocked executables.

If testing how Smart App Control treats a given build (without blocking it), configure it in Evaluation mode and use audit policies as described in the Smart App Control testing guidance.

References:

• Smart App Control overview
• Smart App Control overview#frequently-asked-questions
• Test your app's signature with Smart App Control
• Test your app's signature with Smart App Control#configure-smart-app-control-for-testing
• Test your app's signature with Smart App Control#configure-the-smart-app-control-audit-policy
• App & browser control in the Windows Security App

Hi @Yuvaraj Masilamani ,

Thanks for reaching out.

What you're seeing seems consistent with how Smart App Control can behave when it is running in enforcement mode. A project can still build normally in Visual Studio, but the app may be blocked when it starts if the executable is unsigned or not yet recognized as trusted.

There usually isn't a Visual Studio setting that overrides that behavior for local development builds. In most cases, the practical options are to test on a device or VM where Smart App Control is not enforcing, keep it in Evaluation mode while validating the app, or sign the build with a trusted code-signing certificate.

If you'd like to confirm whether Smart App Control is what is stopping the launch, you can check Event Viewer under Applications and Services Logs > Microsoft > Windows > CodeIntegrity > Operational. Event ID 3077 is typically associated with enforcement blocks, and 3076 is generally used for audit or evaluation scenarios.

If helpful, these Microsoft references go into a bit more detail on the behavior and the available testing options:

Smart App Control overview: https://learn.microsoft.com/en-us/windows/apps/develop/smart-app-control/overview

Test your app's signature with Smart App Control: https://learn.microsoft.com/en-us/windows/apps/develop/smart-app-control/test-your-app-with-smart-app-control

Smart App Control FAQ: https://support.microsoft.com/en-us/topic/what-is-smart-app-control-285ea03d-fa88-4d56-882e-6698afdb7003

Hope this helps! If my answer was helpful, I would greatly appreciate it if you could follow the instructions here so others with the same problem can benefit as well.

• your smart app application has been blocked by windows security applications. just turn off those settings.