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Marshal.FreeBSTR Method

Frees a BSTR using SysFreeString.

[Visual Basic]
Public Shared Sub FreeBSTR( _
   ByVal ptr As IntPtr _
public static void FreeBSTR(
 IntPtr ptr
public: static void FreeBSTR(
 IntPtr ptr
public static function FreeBSTR(
   ptr : IntPtr


The address of the BSTR to be freed.


Exception Type Condition
ArgumentNullException ptr is a null reference (Nothing in Visual Basic).


Like Marshal.FreeCoTaskMem and Marshal.FreeHGlobal, you can use this method to deallocate memory. FreeBSTR calls SysFreeString, a COM API method, which frees memory allocated by any of the following unmanaged methods: SysAllocString, SysAllocStringByteLen, SysAllocStringLen, SysReAllocString, SysReAllocStringLen. You can call unmanaged methods such as these with platform invoke. For details, see Consuming Unmanaged DLL Functions.

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.


Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

.NET Framework Security: 

See Also

Marshal Class | Marshal Members | System.Runtime.InteropServices Namespace | Marshal.FreeCoTaskMem | Marshal.FreeHGlobal