GetIUnknownForObject Method
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Marshal.GetIUnknownForObject Method (Object)


Returns an IUnknown interface from a managed object.

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

public static IntPtr GetIUnknownForObject(
	object o


Type: System.Object

The object whose IUnknown interface is requested.

Return Value

Type: System.IntPtr

The IUnknown pointer for the o parameter.

In managed code, you seldom work directly with the IUnknown interface. However, GetIUnknownForObject is useful when calling a method that exposes a COM object parameter as an IntPtr type, or with custom marshaling. 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. This method provides the opposite functionality of the Marshal.GetObjectForIUnknown method.

You can also use this method on a managed object to obtain an interface pointer to the COM Callable Wrapper for the object.

The following example demonstrates how to retrieve an IUnknown interface for a managed object using the GetIUnknownForObject method.

using System;
using System.Runtime.InteropServices;

class Program

    static void Run()

        // Create an int object
        int obj = 1;

        Console.WriteLine("Calling Marshal.GetIUnknownForObject...");

        // Get the IUnKnown pointer for the Integer object
        IntPtr pointer = Marshal.GetIUnknownForObject(obj);

        Console.WriteLine("Calling Marshal.Release...");

        // Always call Marshal.Release to decrement the reference count.

    static void Main(string[] args)


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

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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