How Can I Catch and Handle Native Exceptions in C#?

Catching Native Exceptions in C# Code

In C# programming, it is possible to catch exceptions that originate from unmanaged libraries, often termed "native exceptions." These exceptions occur when the underlying native code encounters an error that cannot be handled within the managed code.

How to Catch Native Exceptions

To catch native exceptions, you can use the Win32Exception class. This class exposes a NativeErrorCode property that contains the error code generated by the unmanaged library. You can use this property to handle the exception appropriately.

Example Usage

The following example demonstrates how to catch a native exception and handle it using the Win32Exception class:

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, the OpenFile() method attempts to open a file using a native application. If the file cannot be found, access is denied, or there is no application associated with the file type, a native exception is thrown. The catch block uses the Win32Exception class to intercept the exception and handle it appropriately by displaying a message box with the error details.

Note: You do not need to make any special modifications to the try...catch block to catch native exceptions. The standard try...catch mechanism is sufficient for handling both managed and native exceptions.

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