CODEWITHSUNDEEP
.netvb.netexception
Adam Davis
Adam Davis

Reputation: 93565

Why isn't the try/catch catching the access violation?

I put a try/catch block around a bit of code that occasionaly throws an expected exception, but rather than catching it and displaying the message box, it stops the debugger and alerts me that the exception is unhandled.

How do I handle this exception so my code doesn't stop when the exception occurs?

enter image description here

Friend myDevInfo As New devInfo

        ''' <summary>
        ''' Closes the device handle obtained with CreateFile and frees resources.
        ''' </summary>
        ''' 
        Friend Sub CloseDeviceHandle()

            Try
                WinUsb_Free(myDevInfo.winUsbHandle)

                If Not (myDevInfo.deviceHandle Is Nothing) Then
                    If Not (myDevInfo.deviceHandle.IsInvalid) Then
                        myDevInfo.deviceHandle.Close()
                    End If
                End If

            Catch ex As System.AccessViolationException
                MsgBox("System.AccessViolationException")
            Catch ex As Exception
                Throw
            End Try

        End Sub

Upvotes: 4

Views: 2801

Answers (3)

Sohail Siddique
Sohail Siddique

Reputation: 27

Use this attribute on the top of the function that you are using.

 [HandleProcessCorruptedStateExceptions()]

This exception occurs with only unsafe or protected memory. The memory that is not been allocated . If you use this attribute then the clr will detect it and the try-catch block is working fine present in :

System.Runtime.ExceptionServices;

Upvotes: 1

maemmott
maemmott

Reputation: 11

An access violation exception falls into a class of exceptions called 'corrupted state exceptions'. With .Net 4, Microsoft took the decision that these should no longer be caught by try .. catch blocks. Their reasoning is that it takes understanding and care to recover from corrupted state exceptions without causing more damage, and that it is safer for users' data, if the application is closed down.

MSDN will tell you how to reverse this change

Upvotes: 1

Xharze
Xharze

Reputation: 2733

The try...catch block should work as expected, when no debugger is attached.
You can define what exceptions the debugger breaks on under Debug -> Exceptions, I believe the default is to break on AccessViolationException.

Upvotes: 3

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