Marshal.QueryInterface(IntPtr, Guid, IntPtr) Method

Definition

Namespace:

System.Runtime.InteropServices

Assembly:

System.Runtime.InteropServices.dll

Source:

Marshal.cs

Requests a pointer to a specified interface from a COM object.

public:
 static int QueryInterface(IntPtr pUnk, Guid % iid, [Runtime::InteropServices::Out] IntPtr % ppv);

public static int QueryInterface (IntPtr pUnk, ref Guid iid, out IntPtr ppv);

static member QueryInterface : nativeint * Guid * nativeint -> int

Public Shared Function QueryInterface (pUnk As IntPtr, ByRef iid As Guid, ByRef ppv As IntPtr) As Integer

Parameters

pUnk

IntPtr

nativeint

The interface to be queried.

iid

Guid

The interface identifier (IID) of the requested interface.

ppv

IntPtr

nativeint

When this method returns, contains a reference to the returned interface.

Returns

Int32

An HRESULT that indicates the success or failure of the call.

Remarks

The QueryInterface method exposes the IUnknown::QueryInterface method 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.

See also

• AddRef(IntPtr)
• Release(IntPtr)
• GetComInterfaceForObject(Object, Type)
• GetIUnknownForObject(Object)
• GetIDispatchForObject(Object)
• GetObjectForIUnknown(IntPtr)