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Marshal.FreeCoTaskMem Method

Frees a block of memory allocated by the unmanaged COM task memory allocator with Marshal.AllocCoTaskMem.

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

public static void FreeCoTaskMem (
	IntPtr ptr
public static void FreeCoTaskMem (
	IntPtr ptr
public static function FreeCoTaskMem (
	ptr : IntPtr



The address of the memory to be freed.

You can use FreeCoTaskMem to free any memory allocated by AllocCoTaskMem, ReAllocCoTaskMem, or any equivalent unmanaged API. If the ptr parameter is a null reference (Nothing in Visual Basic), the method does nothing.

FreeCoTaskMem exposes the CoTaskMemFree COM API function, which frees all bytes so that you can no longer use the memory pointed to by the ptr parameter. For additional information about CoTaskMemFree, see the MSDN library.

In addition to FreeCoTaskMem, the Marshal class provides two other memory-deallocation methods: Marshal.DestroyStructure and Marshal.FreeHGlobal.


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.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0