Can Standard C# try...catch Blocks Handle Native Exceptions from Unmanaged Libraries?

Can Native Exception Evasion Happen in C#?

When working with external, unmanaged libraries in C#, it's essential to consider the possibility of facing native exceptions originating from deep within those libraries.

Can Standard Try...Catch Capture Native Exceptions?

Fortunately, C# provides a mechanism to catch native exceptions as well. The question is: Can standard try...catch blocks handle these unmanaged exceptions without any modifications?

Answer: Catching Native Exceptions

To catch native exceptions, you can use the Win32Exception class. It offers a property named NativeErrorCode that allows you to examine the error code and handle specific cases accordingly.

For instance, consider the following code snippet:

const int ERROR_FILE_NOT_FOUND = 2;
const int ERROR_ACCESS_DENIED = 5;
const int ERROR_NO_APP_ASSOCIATED = 1155;

void OpenFile(string filePath)
{
    Process process = new Process();

    try
    {
        // Calls native application registered for the file type
        // This may throw a native exception
        process.StartInfo.FileName = filePath;
        process.StartInfo.Verb = "Open";
        process.StartInfo.CreateNoWindow = true;
        process.Start();
    }
    catch (Win32Exception e)
    {
        if (e.NativeErrorCode == ERROR_FILE_NOT_FOUND ||
            e.NativeErrorCode == ERROR_ACCESS_DENIED ||
            e.NativeErrorCode == ERROR_NO_APP_ASSOCIATED)
        {
            MessageBox.Show(this, e.Message, "Error",
                MessageBoxButtons.OK,
                MessageBoxIcon.Exclamation);
        }
    }
}

In this example, we attempt to launch a native application associated with a specific file type. If the application cannot be started, a Win32Exception is thrown with an associated error code. The if statement within the catch block checks for specific error codes and displays an appropriate message.

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