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Marshal::FreeHGlobal Method

Frees memory previously allocated from the unmanaged memory of the process.

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

public:
static void FreeHGlobal(
	IntPtr hglobal
)

Parameters

hglobal
Type: System::IntPtr
The handle returned by the original matching call to AllocHGlobal.

You can use FreeHGlobal to free any memory from the global heap allocated by AllocHGlobal, ReAllocHGlobal, or any equivalent unmanaged API method. If the hglobal parameter is IntPtr::Zero the method does nothing.

FreeHGlobal exposes the LocalFree function from Kernel32.DLL, which frees all bytes so that you can no longer use the memory pointed to by hglobal.

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

Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition Platform Note: Passing an invalid handle value to FreeHGlobal causes an ArgumentException.

The following example demonstrates calling the FreeHGlobal method. This code example is part of a larger example provided for the Marshal class.


// Demonstrate how to call GlobalAlloc and 
// GlobalFree using the Marshal class.
IntPtr hglobal = Marshal::AllocHGlobal(100);
Marshal::FreeHGlobal(hglobal);


The following example demonstrates how to convert the contents of a managed String class to unmanaged memory and then dispose of the unmanaged memory when done.


using namespace System;
using namespace System::Runtime::InteropServices;

#include <iostream>                                                 // for printf


int main()
{
    // Create a managed string.
    String^ managedString = "Hello unmanaged world (from the managed world).";

    // Marshal the managed string to unmanaged memory.
    char* stringPointer = (char*) Marshal::StringToHGlobalAnsi(managedString ).ToPointer();

    printf("stringPointer = %s\n", stringPointer);

    // Always free the unmanaged string.
    Marshal::FreeHGlobal(IntPtr(stringPointer));

    return 0;
}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

  • SecurityCriticalAttribute 

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

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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