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Marshal.ReAllocHGlobal Method

Updated: January 2011

Resizes a block of memory previously allocated with AllocHGlobal.

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

static member ReAllocHGlobal : 
        pv:IntPtr * 
        cb:IntPtr -> IntPtr 


Type: System.IntPtr
A pointer to memory allocated with AllocHGlobal.
Type: System.IntPtr
The new size of the allocated block. This is not a pointer; it is the byte count you are requesting, cast to type IntPtr. If you pass a pointer, it is treated as a size.

Return Value

Type: System.IntPtr
A pointer to the reallocated memory. This memory must be released using Marshal.FreeHGlobal.


There is insufficient memory to satisfy the request.

ReAllocHGlobal is one of two memory reallocation API methods in the Marshal class. (Marshal.ReAllocCoTaskMem is the other.)

This method exposes the Win32 GlobalReAlloc function from Kernel32.dll. The returned pointer can differ from the original. If it is different, the contents of the original memory block have been copied to the new block, and the original memory block has been freed.

.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.




January 2011

Clarified that size is treated as a number, not as a pointer.

Customer feedback.

January 2011

Clarified what happens when the method returns a different pointer.

Content bug fix.