If structure is a value type, it can be boxed or unboxed. If it is boxed, it is unboxed before copying.

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

Marshal.StructureToPtr(object, IntPtr, bool) 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 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 Marshal.DestroyStructure(IntPtr, Type) method before you free the memory block.

If you use the Marshal.StructureToPtr(object, IntPtr, bool) 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 Marshal.StructureToPtr(object, IntPtr, bool) is as follows: