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Marshal::StructureToPtr<T> Method (T, IntPtr, Boolean)

[Supported in the .NET Framework 4.5.1 and later versions]

Marshals data from a managed object of a specified type to an unmanaged block of memory.

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

generic<typename T>
static void StructureToPtr(
	T structure, 
	IntPtr ptr, 
	bool fDeleteOld

Type Parameters


The type of the managed object.


Type: T

A managed object that holds the data to be marshaled. The object must be a structure or an instance of a formatted class.

Type: System::IntPtr

A pointer to an unmanaged block of memory, which must be allocated before this method is called.

Type: System::Boolean

true to call the DestroyStructure<T>(IntPtr) method on the ptr parameter before this method copies the data. The block must contain valid data. Note that passing false when the memory block already contains data can lead to a memory leak.


structure is a reference type that is not a formatted class.

A formatted class is a reference type whose layout is specified by the StructLayoutAttribute attribute, as either LayoutKind::Explicit or LayoutKind::Sequential.

StructureToPtr<T>(T, IntPtr, Boolean) copies the contents of structure to the pre-allocated block of memory that the ptr parameter points to. If structure contains reference types that marshal to COM interface pointers (interfaces, classes without layout, and System::Object), the managed objects are kept alive with reference counts. All other reference types (for example, strings and arrays) are marshaled to copies. To release these managed or unmanaged objects, you must call the DestroyStructure<T>(IntPtr) method before you free the memory block.

If you use the StructureToPtr<T>(T, IntPtr, Boolean) method to copy a different instance to the memory block at a later time, specify true for fDeleteOld to remove reference counts for reference types in the previous instance. Otherwise, the managed reference types and unmanaged copies are effectively leaked.

The overall pattern for using StructureToPtr<T>(T, IntPtr, Boolean) is as follows:

  1. On the first call to the StructureToPtr method after a memory block has been allocated, fDeleteOld must be false, because there are no contents to clear.

    Important noteImportant

    Specify true for fDeleteOld only if the block contains valid data.

  2. If you copy a different instance to the memory block, and the object contains reference types, fDeleteOld must be true to free reference types in the old contents.

  3. If the object contains reference types, you must call the DestroyStructure method before you free the memory block.


To pin an existing structure instead of copying it, use the System.Runtime.InteropServices::GCHandle type to create a pinned handle for the structure. For details on how to pin, see Copying and Pinning.

.NET Framework

Supported in: 4.6, 4.5.1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1

  • SecurityCriticalAttribute 

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

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