Why Doesn't My Try-Catch Block Catch AccessViolationException in .NET When Using COM Objects?

Addressing AccessViolationException in .NET COM Interactions

When using COM objects within .NET applications, System.AccessViolationException can unexpectedly bypass try-catch blocks. This often leads to debugging difficulties and application crashes outside the development environment.

The Role of Corrupted State Exceptions (CSE)

This behavior is primarily due to .NET 4.0's Corrupted State Exceptions (CSE) mechanism. Certain exceptions, including AccessViolationException, are classified as CSEs, signaling a potentially critical process state. Standard managed code try-catch blocks cannot intercept these exceptions.

Strategies for Handling CSEs

To effectively manage AccessViolationException originating from COM object calls, consider these approaches:

1. Target .NET Framework 3.5: Recompile your application for the .NET Framework 3.5. Running this 3.5 assembly within a .NET 4.0 environment might resolve the issue.

2. Configure Legacy Exception Policy: Modify your application's configuration file (app.config or web.config) by adding the following within the <configuration></configuration> element:

<legacyCorruptedStateExceptionsPolicy enabled="true" />

Setting enabled="true" allows the runtime to handle CSEs in a way compatible with earlier .NET versions.

3. Employ the HandleProcessCorruptedStateExceptions Attribute: Annotate methods susceptible to CSEs with the [HandleProcessCorruptedStateExceptions] attribute. Consult Microsoft's documentation for detailed usage instructions. This attribute signals the runtime to allow the method to handle CSEs.

These methods provide alternative ways to handle exceptions that would otherwise evade standard exception handling mechanisms in .NET when working with COM objects.

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