marshal.cs

/* C++ */
typedef struct {
	unsigned long		address;
	unsigned long		length;
	unsigned char *		data;
} ELEMENT, *PELEMENT;

unsigned long SetElement(ELEMENT Element);

/* C# */

[StructLayout(LayoutKind.Sequential, Pack = 1)]
public unsafe struct Element
{
	public unsigned long address;
	public unsigned long length;
	public IntPtr data;
}

[DllImport("MyDll.DLL", EntryPoint = "SetElement", CharSet = CharSet.Auto)]
public static unsafe extern unsigned long SetElement(Element element);


FileInfo fi = new FileInfo(filename);

Element element = new Element
{
	address = startAddress,
	length = (unsigned int)fi.Length,
};
element.data = Marshal.AllocHGlobal((unsigned int)fi.Length);

byte[] file = File.ReadAllBytes(filename);

Marshal.Copy(file, 0, element.data, (unsigned int)fi.Length);

SetElement(element);

Marshal.FreeHGlobal(element.data);