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Troubleshooting COMExceptions in WPF .NET Framework Applications: A Developer's Guide

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This article addresses a common issue encountered by developers using Windows Presentation Foundation (WPF) applications on systems running Windows 7 or Windows Server 2008 R2 after installing .NET Framework 4.7. Specifically, it focuses on resolving the System.Runtime.InteropServices.COMException that can arise in these environments. This error can disrupt the functionality of WPF applications and negatively impact user experience. Understanding the root cause and applying the correct resolution is crucial for maintaining application stability and performance. This guide provides a comprehensive walkthrough to diagnose and fix this particular COMException problem.

Symptoms

The issue typically manifests in a specific scenario involving touch-enabled devices running older operating systems. Let’s outline the conditions that lead to this COMException:

  • Operating System: You are using a touch-enabled device running Microsoft Windows 7 Service Pack 1 (SP1) or Windows Server 2008 R2 SP1. These operating systems, while robust, require specific updates to ensure compatibility with newer software frameworks.
  • WPF Applications: You have one or more Windows Presentation Foundation (WPF) applications installed and running on the affected device. WPF is a powerful framework for building visually engaging desktop applications, but like all software, it can encounter compatibility issues.
  • Prerequisite Update: The system has been updated with the “May 2017 Preview of Quality Rollup for the .NET Framework 4.6, 4.6.1, and 4.6.2” (KB 4104606). This update, while intended to improve quality, sets the stage for the subsequent issue.
  • .NET Framework 4.7 Installation: Following the prerequisite update, you install the .NET Framework 4.7 on the same device. This installation, in combination with the previous updates and operating system, triggers the COMException.

When these conditions are met, your WPF applications may start failing and display error messages. The error message usually presents itself as a nested exception, indicating a problem during application initialization.

Here is the typical error message structure you might encounter:

Exception type: System.TypeInitializationException
Message: The type initializer for 'MS.Win32.Penimc.UnsafeNativeMethods' threw an exception.
InnerException: System.Runtime.InteropServices.COMException
Message of the inner exception: Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))

Error Message Example

This error message indicates that the TypeInitializationException is the primary issue, but the underlying cause is a COMException. Specifically, the inner exception “Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))” points to a problem with Component Object Model (COM) registration. In this context, it suggests that a necessary COM component, likely related to input handling (MS.Win32.Penimc.UnsafeNativeMethods), is not correctly registered after the .NET Framework 4.7 installation. This is particularly relevant in touch-enabled environments where input mechanisms rely on COM components.

Resolution

The most straightforward and recommended solution to resolve this COMException is to install a specific update released by Microsoft. This update is designed to address the COM registration issue introduced by the combination of the May 2017 Preview Rollup and .NET Framework 4.7 on Windows 7 SP1 and Windows Server 2008 R2 SP1.

The recommended update is the “July 25, 2017, update for the .NET Framework 4.6, 4.6.1, 4.6.2, and 4.7”. This update is available through the Microsoft Update Catalog.

Here are the specific updates to download and install based on your operating system:

Windows 7 SP1 and Windows Server 2008 R2 SP1

For systems running Windows 7 SP1 or Windows Server 2008 R2 SP1, you need to download and install the stand-alone package from the Microsoft Update Catalog.

For more detailed information about this specific update, you can refer to the associated Knowledge Base article:

Windows 8.1 and Windows Server 2012 R2

While the primary issue is observed on Windows 7 and Server 2008 R2, a related update is also available for Windows 8.1 and Windows Server 2012 R2. If you are experiencing similar COMException issues in WPF applications on these operating systems after installing .NET Framework 4.7, applying the following update is recommended.

For more information regarding this update for Windows 8.1 and Server 2012 R2, consult the following KB article:

Windows Server 2012

Similarly, for Windows Server 2012, a specific update is available to address potential COMException issues in WPF applications after the .NET Framework 4.7 installation.

Details about this update for Windows Server 2012 can be found in this KB article:

Installation Steps:

  1. Navigate to the appropriate Microsoft Update Catalog link for your operating system.
  2. Download the stand-alone package for the specified KB number.
  3. Run the downloaded package (.msu file) and follow the on-screen instructions to install the update.
  4. Restart your system after the installation is complete to ensure the update is fully applied.

Applying these updates should resolve the COMException issue and restore the normal functionality of your WPF applications.

Workaround

If installing the recommended update is not immediately feasible, or if you need a temporary solution, there are a couple of workarounds you can employ. These workarounds are not permanent fixes but can help you mitigate the issue while you plan for a more comprehensive solution. The workarounds include:

  1. Uninstalling and Reinstalling .NET Framework 4.7: This process can sometimes correct the COM registration issues.
  2. Temporarily Disabling the Affected WPF Touch Component: If the issue is specifically related to touch input, disabling touch and stylus support for WPF applications can bypass the problem.

Let’s explore each workaround in detail.

Uninstall the .NET Framework 4.7

Uninstalling and then reinstalling .NET Framework 4.7 can sometimes resolve configuration problems that might have occurred during the initial installation, including issues with COM component registration. This is a more involved workaround compared to just installing an update, but it can be effective in certain situations.

Here are the steps to uninstall .NET Framework 4.7:

  1. Open Control Panel: Click on the Start Menu and select “Control Panel”. If you are using Category view, click on “Programs” and then “Uninstall a program”. If you are using Icon view, directly select “Programs and Features”.

    Control Panel Uninstall Program

  2. Locate .NET Framework 4.7: In the “Uninstall or change a program” window, find “Microsoft .NET Framework 4.7” in the list of installed programs. The list is usually sorted alphabetically, so scroll down to the “M” section.

  3. Select Uninstall/Change: Once you have located “Microsoft .NET Framework 4.7”, select it by clicking on it. Then, click the “Uninstall/Change” button that appears in the toolbar above the program list, or right-click on the entry and select “Uninstall/Change”.

  4. .NET Framework 4.7 Maintenance Wizard: The “.NET Framework 4.7 Maintenance” wizard will launch. In this wizard, select the option “Remove .NET Framework 4.7 from this computer”. This option will initiate the uninstallation process.

  5. Click Next: After selecting “Remove .NET Framework 4.7 from this computer”, click the “Next” button to proceed.

  6. Warning Window (If Applicable): In some cases, a warning window might appear during the uninstallation process. If you see a warning, carefully read the message. If it prompts you to continue with the uninstallation, select “Continue” to proceed.

  7. Wait for Uninstallation: The uninstallation process will now begin. This may take some time, depending on your system configuration. Allow the uninstallation to complete without interruption. A progress bar will usually indicate the status of the uninstallation.

Once the uninstallation is complete, you will need to restart your computer for the changes to take full effect. After restarting, you can proceed with reinstalling .NET Framework 4.7.

Reinstall the .NET Framework 4.7

After successfully uninstalling .NET Framework 4.7, you need to reinstall it to restore the framework and hopefully resolve the COMException issue. There are two primary methods for reinstalling .NET Framework 4.7:

Method 1: Manually Download and Install the .NET Framework 4.7

This method involves downloading the .NET Framework 4.7 installer directly from the Microsoft website and then running the installer.

  1. Download the Web Installer: Go to the Microsoft download page for .NET Framework 4.7. You can typically find this by searching for “Download .NET Framework 4.7” on a search engine like Bing or Google. Look for the official Microsoft link, usually starting with go.microsoft.com or microsoft.com. Download the web installer for .NET Framework 4.7. The web installer is a smaller download that requires an internet connection during installation to download the necessary components.

  2. Run the Installer: Once the download is complete, locate the downloaded file (usually named something like dotnetfx47_full_x86_x64_web.exe) and run it. Double-click the file to start the installation process.

  3. Follow Installation Instructions: The .NET Framework 4.7 installer will launch. Follow the on-screen instructions to complete the installation. This typically involves accepting the license terms and clicking “Install”. The installer will download and install the necessary files. Ensure you have a stable internet connection during this process.

  4. Restart Your Computer: After the installation is finished, you will likely be prompted to restart your computer. Restart your system to finalize the installation and ensure all components are correctly registered.

Method 2: Install via Windows Update

Another way to reinstall .NET Framework 4.7 is through Windows Update. This method is particularly useful if you are unsure about downloading the correct installer or prefer to manage updates through the Windows Update interface.

  1. Open Windows Update: Click on the Start Menu and search for “Windows Update”. Select “Windows Update settings” or “Check for updates”. This will open the Windows Update control panel or settings page.

    Windows Update

  2. Check for Updates Online: In the Windows Update window, click on the “Check online for updates from Microsoft Update” link (or similar wording depending on your Windows version). This will force Windows Update to scan for available updates from Microsoft servers, including optional updates.

  3. Optional Updates Available: After the update search completes, if .NET Framework 4.7 is available as an optional update (it might be listed if it was previously uninstalled or if Windows Update detects it is needed), you will see a message indicating “Optional Updates available” or similar. Click on this message or the link to view optional updates.

  4. Locate and Select .NET Framework 4.7: In the list of optional updates, find “Microsoft .NET Framework 4.7 for Windows 7 and Windows Server 2008 R2” (or similar, depending on your operating system). Select the checkbox next to this entry to choose it for installation.

  5. Click OK: After selecting .NET Framework 4.7, click “OK” to confirm your selection and return to the main Windows Update window.

  6. Install Updates: Click the “Install updates” button in the Windows Update window to start the installation process for the selected updates, including .NET Framework 4.7.

  7. Wait for Installation: Windows Update will now download and install .NET Framework 4.7 and any other selected updates. This process may take some time. Allow it to complete without interrupting.

  8. Restart Your Computer: Once the installation is complete, Windows Update will likely prompt you to restart your computer. Restart your system to finalize the installation.

After reinstalling .NET Framework 4.7 using either method, check if the COMException issue in your WPF applications is resolved.

Temporarily Disable Touch and Stylus Support for WPF Applications

If the COMException is indeed related to touch input handling as suggested by the error message (MS.Win32.Penimc.UnsafeNativeMethods), a temporary workaround is to disable touch and stylus support specifically for WPF applications. This can bypass the problematic COM component and allow your applications to run without the exception.

There are two ways to disable touch and stylus support:

Method 1: Application Configuration

This method disables touch and stylus input for a specific WPF application by modifying its application configuration file. This is a per-application setting.

  1. Locate Application Configuration File: Find the main executable file (.exe) of your WPF application. In the same directory, look for a configuration file. The configuration file usually has the same name as the executable but with a .config extension (e.g., if your application executable is MyApp.exe, the config file might be MyApp.exe.config). If a config file doesn’t exist, you may need to create one.

  2. Edit or Create Configuration File: Open the configuration file in a text editor like Notepad. If the file doesn’t exist, create a new text file and save it with the .config extension in the same directory as the application executable.

  3. Add Runtime Configuration: Inside the configuration file, add the following XML structure within the <configuration> element. If <configuration> element doesn’t exist, create it as the root element of the XML file.

    <configuration>
  <runtime>
    <AppContextSwitchOverrides value=" Switch.System.Windows.Input.Stylus.DisableStylusAndTouchSupport=true"/>
  </runtime>
</configuration>

    If you already have a <configuration> element, just add the <runtime> and <AppContextSwitchOverrides> elements within it. If you have an existing <runtime> element, add the <AppContextSwitchOverrides> element inside it, or append the Switch.System.Windows.Input.Stylus.DisableStylusAndTouchSupport=true switch to the existing value attribute if there are other switches already defined, separating them with a semicolon (;).

  4. Save the Configuration File: Save the modified configuration file.

  5. Restart Application: Close and restart your WPF application. The touch and stylus input should now be disabled for this specific application.

Method 2: Registry Modification (Machine-Global)

This method disables touch and stylus input for all WPF applications on the machine by modifying the Windows Registry. Use this method with caution as incorrect registry modifications can cause serious system problems.

Warning: Modifying the registry incorrectly can lead to severe issues that may require you to reinstall your operating system. Proceed with extreme caution and at your own risk. It is recommended to back up your registry before making any changes.

  1. Open Registry Editor: Press Windows Key + R to open the Run dialog. Type regedit and press Enter. This will open the Registry Editor.

    Registry Editor

  2. Navigate to Registry Key: In the Registry Editor, navigate to the following registry key path:

    HKEY_LOCAL_MACHINE\Software\[Wow6432Node\]Microsoft\.NETFramework\AppContext\Switch.System.Windows.Input.Stylus

    • If you are on a 64-bit version of Windows, you might see the Wow6432Node in the path. If you are on a 32-bit version, you will not see Wow6432Node.
    • If the AppContext key or the Switch.System.Windows.Input.Stylus key does not exist, you may need to create them. Right-click on the parent key (e.g., .NETFramework or AppContext), select “New” -> “Key”, and name the new key accordingly.

  3. Create or Modify Value: In the Switch.System.Windows.Input.Stylus key, you need to create or modify a value named DisableStylusAndTouchSupport.

    • If the DisableStylusAndTouchSupport value already exists, double-click it to modify it.
    • If it does not exist, right-click in the right-hand pane of the Registry Editor, select “New” -> “String Value”. Name the new value DisableStylusAndTouchSupport.

  4. Set Value Data: Double-click on the DisableStylusAndTouchSupport value to edit its data. In the “Value data” field, enter true.

    • Type: String (REG_SZ)
    • Value: true

  5. Click OK: Click “OK” to save the changes.

  6. Restart System (Recommended): While a system restart might not always be strictly necessary for registry changes to take effect for applications, it is generally recommended to restart your computer after modifying the registry to ensure all changes are properly loaded.

After applying either the application configuration or registry workaround, touch and stylus input should be disabled for WPF applications. Check if this resolves the COMException issue. Remember that this is a temporary workaround, and the permanent solution is to install the recommended update.

If you found this guide helpful in resolving your COMException issues in WPF applications, or if you have any further questions or experiences to share, please feel free to leave a comment below! Your feedback can help other developers facing similar challenges.

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