Every time a COM interface pointer enters the common language runtime, it is wrapped in a runtime callable wrapper. If you are unfamiliar with the features of this wrapper, see Runtime Callable Wrapper.

This method is used to explicitly control the lifetime of a COM object used from managed code. You should use this method to free the underlying COM object that holds references to resources in a timely manner or when objects must be freed in a specific order.

The runtime callable wrapper has a reference count that is incremented every time a COM interface pointer is mapped to it. The ReleaseComObject method decrements the reference count of a runtime callable wrapper. When the reference count reached zero, the runtime releases all its references on the unmanaged COM object, and throws a System..::.NullReferenceException if you attempt to use the object further. If the same COM interface is passed more than once from unmanaged to managed code, the reference count on the wrapper is incremented every time and calling ReleaseComObject returns the number of remaining references.

Note:
To ensure that the runtime callable wrapper and the original COM object are released, construct a loop from which you call this method until the returned reference count reaches zero.

Note:

This method uses SecurityAction..::.LinkDemand to prevent it from being called from untrusted code; only the immediate caller is required to have SecurityPermissionAttribute..::.UnmanagedCode permission. If your code can be called from partially trusted code, do not pass user input to Marshal class methods without validation. For important limitations on using the LinkDemand member, see Demand vs. LinkDemand.

• SecurityPermission 

  for permission to call unmanaged code.

  Associated enumeration: UnmanagedCode Security action: LinkDemand

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

.NET Framework

.NET Compact Framework

Reference