c# - Marshal.Copy, copying an array of IntPtr into an IntPtr -

i can't figure out how copy(intptr[], int32, intptr, int32) method works. though copy data contained in multiple intptrs single intptr (as msdn states) apparently doesn't work expected:

intptr[] ptrarray = new intptr[] {     marshal.allochglobal(1),     marshal.allochglobal(2)  };   marshal.writebyte(ptrarray[0], 0, 0xc1);   // allocate total size.  intptr ptr = marshal.allochglobal(3);   marshal.copy(ptrarray, 0, ptr, ptrarray.length);   // expect read 0xc1 value random!!  byte value = marshal.readbyte(ptr, 0); 

does know if i'm using method not purpose?

    static void main(string[] args)     {         intptr[] ptrarray = new intptr[]         {             marshal.allochglobal(1),             marshal.allochglobal(2)         };          marshal.writebyte(ptrarray[0], 0, 100);          int size = marshal.sizeof(typeof(intptr)) * ptrarray.length;         intptr ptr = marshal.allochglobal(size);          marshal.copy(ptrarray, 0, ptr, ptrarray.length);          // have native pointer ptr, points 2 pointers,         // each of thme points own memory (size 1 , 2).          // let's read first intptr ptr:         intptr p = marshal.readintptr(ptr);          // let's read byte p:         byte b = marshal.readbyte(p);          console.writeline((int)b);    // prints 100          // do: release intptr     } 

read explanations in comments.