Marshal.QueryInterface Method
Requests a pointer to a specified interface from a COM object.
[Visual Basic] Public Shared Function QueryInterface( _ ByVal pUnk As IntPtr, _ ByRef iid As Guid, _ <Out()> ByRef ppv As IntPtr _ ) As Integer [C#] public static int QueryInterface( IntPtr pUnk, ref Guid iid, out IntPtr ppv ); [C++] public: static int QueryInterface( IntPtr pUnk, Guid* iid, [ Out ] IntPtr* ppv ); [JScript] public static function QueryInterface( pUnk : IntPtr, iid : Guid, ppv : IntPtr ) : int;
Parameters
- pUnk
- The interface to be queried.
- iid
- A Guid, passed by reference, that is the interface identifier (IID) of the requested interface.
- ppv
- When this method returns, contains a reference to the returned interface.
Return Value
The returned interface.
Remarks
The QueryInterface method exposes the IUnknown::QueryInterface of a COM object, which attempts to obtain a specific interface pointer. Using QueryInterface on a COM object is the same as performing a cast operation in managed code. Calling an object with this method causes the reference count to increment on the interface pointer before the pointer is returned. Always use Marshal.Release to decrement the reference count once you have finished with the pointer. To obtain an IntPtr value that represents a IUnknown interface pointer, you can call Marshal.GetComInterfaceForObject, Marshal.GetIUnknownForObject, or Marshal.GetIDispatchForObject.
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.
Requirements
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family
.NET Framework Security:
- SecurityPermission for operating with unmanaged code. Associated enumeration: SecurityPermissionFlag.UnmanagedCode.
See Also
Marshal Class | Marshal Members | System.Runtime.InteropServices Namespace | AddRef | Release | GetComInterfaceForObject | GetIUnknownForObject | GetIDispatchForObject | GetObjectForIUnknown
