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MSDN Library

Marshal.QueryInterface Method

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

Namespace:  System.Runtime.InteropServices
Assemblies:   System.Runtime.InteropServices (in System.Runtime.InteropServices.dll)
  mscorlib (in mscorlib.dll)

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


Type: System.IntPtr

The interface to be queried.

Type: System.Guid

The interface identifier (IID) of the requested interface.

Type: System.IntPtr

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

Return Value

Type: System.Int32
An HRESULT that indicates the success or failure of the call.

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.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library

  • SecurityCriticalAttribute 

    requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

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