Marshal.StructureToPtr Method (Object, IntPtr, Boolean)


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

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

public static void StructureToPtr(
	object structure,
	IntPtr ptr,
	bool fDeleteOld


Type: System.Object

A managed object that holds the data to be marshaled. This 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 Marshal.DestroyStructure 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.

Exception Condition

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


structure is a generic type.

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 StructLayoutAttribute attribute, as either LayoutKind.Explicit or LayoutKind.Sequential.

StructureToPtr 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 Marshal.DestroyStructuremethod before you free the memory block.

If you use the StructureToPtr 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 typesand unmanaged copies are effectively leaked.

The overall pattern for using StructureToPtr is as follows:

  1. On the first call to the StructureToPtrmethod after a memory block has been allocated, fDeleteOldmust befalse, because there are no contents to clear.


    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.

The following example creates a managed structure, transfers it to unmanaged memory using the StructureToPtr method, and then transfers it back to managed memory using the PtrToStructure method.

using System;
using System.Runtime.InteropServices;

public struct Point
    public int x;
    public int y;

class Example

    static void Main()

        // Create a point struct.
        Point p;
        p.x = 1;
        p.y = 1;

        Console.WriteLine("The value of first point is " + p.x + " and " + p.y + ".");

        // Initialize unmanged memory to hold the struct.
        IntPtr pnt = Marshal.AllocHGlobal(Marshal.SizeOf(p));


            // Copy the struct to unmanaged memory.
            Marshal.StructureToPtr(p, pnt, false);

            // Create another point.
            Point anotherP;

            // Set this Point to the value of the 
            // Point in unmanaged memory. 
            anotherP = (Point)Marshal.PtrToStructure(pnt, typeof(Point));

            Console.WriteLine("The value of new point is " + anotherP.x + " and " + anotherP.y + ".");

            // Free the unmanaged memory.




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

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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