AccessViolationException Class (System)

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.NET Framework Class Library
AccessViolationException Class

The exception that is thrown when there is an attempt to read or write protected memory.

Inheritance Hierarchy
System.Object
  System.Exception
    System.SystemException
      System.AccessViolationException

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)
Syntax
Visual Basic
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public Class AccessViolationException _
	Inherits SystemException
C#
[SerializableAttribute]
[ComVisibleAttribute(true)]
public class AccessViolationException : SystemException
Visual C++
[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class AccessViolationException : public SystemException
F#
[<SerializableAttribute>]
[<ComVisibleAttribute(true)>]
type AccessViolationException =  
    class
        inherit SystemException
    end

The AccessViolationException type exposes the following members.

Constructors
  Name Description
Public method AccessViolationException() Initializes a new instance of the AccessViolationException class with a system-supplied message that describes the error.
Public method AccessViolationException(String) Initializes a new instance of the AccessViolationException class with a specified message that describes the error.
Protected method AccessViolationException(SerializationInfo, StreamingContext) Initializes a new instance of the AccessViolationException class with serialized data.
Public method AccessViolationException(String, Exception) Initializes a new instance of the AccessViolationException class with a specified error message and a reference to the inner exception that is the cause of this exception.
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Properties
  Name Description
Public property Data Gets a collection of key/value pairs that provide additional user-defined information about the exception. (Inherited from Exception.)
Public property HelpLink Gets or sets a link to the help file associated with this exception. (Inherited from Exception.)
Protected property HResult Gets or sets HRESULT, a coded numerical value that is assigned to a specific exception. (Inherited from Exception.)
Public property InnerException Gets the Exception instance that caused the current exception. (Inherited from Exception.)
Public property Message Gets a message that describes the current exception. (Inherited from Exception.)
Public property Source Gets or sets the name of the application or the object that causes the error. (Inherited from Exception.)
Public property StackTrace Gets a string representation of the immediate frames on the call stack. (Inherited from Exception.)
Public property TargetSite Gets the method that throws the current exception. (Inherited from Exception.)
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Methods
  Name Description
Public method Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method GetBaseException When overridden in a derived class, returns the Exception that is the root cause of one or more subsequent exceptions. (Inherited from Exception.)
Public method GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method GetObjectData When overridden in a derived class, sets the SerializationInfo with information about the exception. (Inherited from Exception.)
Public method GetType Gets the runtime type of the current instance. (Inherited from Exception.)
Protected method MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method ToString Creates and returns a string representation of the current exception. (Inherited from Exception.)
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Events
  Name Description
Protected event SerializeObjectState Occurs when an exception is serialized to create an exception state object that contains serialized data about the exception. (Inherited from Exception.)
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Remarks

An access violation occurs in unmanaged or unsafe code when the code attempts to read or write to memory that has not been allocated, or to which it does not have access. This usually occurs because a pointer has a bad value. Not all reads or writes through bad pointers lead to access violations, so an access violation usually indicates that several reads or writes have occurred through bad pointers, and that memory might be corrupted. Thus, access violations almost always indicate serious programming errors. In the .NET Framework version 2.0, an AccessViolationException clearly identifies these serious errors.

In programs consisting entirely of verifiable managed code, all references are either valid or null, and access violations are impossible. An AccessViolationException occurs only when verifiable managed code interacts with unmanaged code or with unsafe managed code.

Version Information

This exception is new in the .NET Framework version 2.0. In earlier versions of the .NET Framework, an access violation in unmanaged code or unsafe managed code is represented by a NullReferenceException in managed code. A NullReferenceException is also thrown when a null reference is dereferenced in verifiable managed code, an occurrence that does not involve data corruption, and there is no way to distinguish between the two situations in versions 1.0 or 1.1.

Administrators can allow selected applications to revert to the behavior of the .NET Framework version 1.1. Place the following line in the <runtime> Element section of the configuration file for the application:

<legacyNullReferenceExceptionPolicy enabled = "1"/>
Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Thread Safety
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
See Also

Reference

System Namespace

Other Resources

Handling and Throwing Exceptions
Community Content

Anam khan
Hardware memory corruption
In programs consisting entirely of verifiable managed code, all references are either valid or null, and access violations are impossible. $0$0 $0 $0"Impossible" seems like too strong a statement. If the machine has bad RAM, a bit could flip, and a pointer could be corrupted, even if the code is entirely verifiable.$0 $0$0 $0

Anam khan
if trying to catch this exception...
You cannot catch this exception byy default in .NET 4 and later versions of the full CLR. You need to decorate your method with the catch block, add the attribute [HandleProcessCorruptedStateExceptions] . See http://msdn.microsoft.com/en-us/library/system.runtime.exceptionservices.handleprocesscorruptedstateexceptionsattribute.aspx . Thanks StackOverflow* for helping me find the answer, http://stackoverflow.com/questions/3561545/how-to-terminate-a-program-when-it-crashes-which-should-just-fail-a-unit-test-i .

Anam khan
this is serious
quote : "An access violation occurs in unmanaged or unsafe code when the code attempts to read or write to memory that has not been allocated, or to which it does not have access. This usually occurs because a pointer has a bad value. Not all reads or writes through bad pointers lead to access violations, so an access violation usually indicates that several reads or writes have occurred through bad pointers, and that memory might be corrupted. Thus, access violations almost always indicate serious programming errors. In the .NET Framework version 2.0, an AccessViolationException clearly identifies these serious errors." $0$0 $0 $0I do not write unmanaged code, this exception drives me CRAZYYYY when I debug ASPNET web application hosted i IIS in VS 2008 !!!!! System.Web throws it so, go back to work MS and fix those serious errors, damn it. $0