Marshal.AllocHGlobal Method (IntPtr) (System.Runtime.InteropServices)

.NET Framework Class Library

Marshal..::.AllocHGlobal Method (IntPtr)

Updated: July 2009

Allocates memory from the process's unmanaged memory.

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

Syntax

Visual Basic (Declaration)

<SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags := SecurityPermissionFlag.UnmanagedCode)> _
Public Shared Function AllocHGlobal ( _
    cb As IntPtr _
) As IntPtr

Visual Basic (Usage)

Dim cb As IntPtr
Dim returnValue As IntPtr

returnValue = Marshal.AllocHGlobal(cb)

[SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
public static IntPtr AllocHGlobal(
    IntPtr cb
)

Visual C++

[SecurityPermissionAttribute(SecurityAction::LinkDemand, Flags = SecurityPermissionFlag::UnmanagedCode)]
public:
static IntPtr AllocHGlobal(
    IntPtr cb
)

JScript

public static function AllocHGlobal(
    cb : IntPtr
) : IntPtr

Parameters

cb: Type: System..::.IntPtr
The number of bytes in memory required.

Return Value

Type: System..::.IntPtr
An IntPtr to the newly allocated memory. This memory must be released using the Marshal..::.FreeHGlobal method.

Exceptions

Exception	Condition
OutOfMemoryException	There is insufficient memory to satisfy the request.

Remarks

AllocHGlobal is one of two memory allocation API methods in the Marshal class. (Marshal..::.AllocCoTaskMem is the other.) This method exposes the Win32 LocalAlloc function from Kernel32.dll.

When AllocHGlobal calls LocalAlloc, it passes a LMEM_FIXED flag, which causes the allocated memory to be locked in place. Also, the allocated memory is not zero-filled.

Note:
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.

Note:

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.

.NET Framework Security

SecurityPermission
for permission to call unmanaged code.
Associated enumeration: UnmanagedCode Security action: LinkDemand

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

Version Information