Assembly: mscorlib (in mscorlib.dll)
The interface reference count to increment.
Return ValueThe new value of the reference count on the pUnk parameter.
The common language runtime manages the reference count of a COM object for you, making it unnecessary to use this method directly. In rare cases, such as testing a custom marshaler, you might find it necessary to manipulate an object's lifetime manually. After calling AddRef, you must decrement the reference count by using a method such as Marshal.Release. Do not rely on the return value of AddRef, as it can sometimes be unstable.
You can call Marshal.GetComInterfaceForObject, Marshal.GetIUnknownForObject, or Marshal.GetIDispatchForObject to obtain an IntPtr value that represents an IUnknown interface pointer. You can also use these methods and the AddRef method on managed objects to obtain the COM interfaces represented by the managed object's COM callable wrapper. If you are not familiar with the details this wrapper type, see COM Callable Wrapper. For additional information about IUnknown::AddRef, see the MSDN Library.
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.
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.