C#

int bitsInCell = Marshal.SizeOf(data[0]) * 8;

// Create buffer
Int32[] buffer = new Int32[10];
buffer[5] = 1;

// Allocate and copy to unmanaged memory
IntPtr ptr = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(Int32)) * 10);
Marshal.Copy(buffer, 0, ptr, 10);

// Change buffer, so we can see that the ptr has restores the
//   old value
buffer[5] = 2;

// Copy from unmanged memory back to array
Marshal.Copy(ptr, buffer, 0, 10);

// Free memory, or else we will leak it
Marshal.FreeHGlobal(ptr);

<br />
// Create buffer<br />
Int32[] buffer = new Int32[10];<br />
buffer[5] = 1;<br />
<br />
// Allocate and copy to unmanaged memory<br />
IntPtr ptr = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(Int32)) * 10);<br />
Marshal.Copy(buffer, 0, ptr, 10);<br />
<br />
// **** Need to add this, otherwise c# complains about not being able to convert IntPtr to int<br />
int bptr = (int)ptr;<br />
ocx.PutData(ref bptr, Marshal.SizeOf(typeof(Int32)) * 10);<br />
<br />
// Change buffer, so we can see that the ptr has restored the<br />
//   old value<br />
buffer[5] = 2;<br />
<br />
// **** Allocate another are to retrieve data<br />
IntPtr ptr2 = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(Int32)) * 10);<br />
int bptr2 = (int)ptr2;<br />
<br />
ocx.GetData(ref bptr2);<br />
// **** Here there is the problem: when GetData() returns, <br />
// the bptr2 variable has been changed and its value is = bptr = (int ptr) <br />
<br />
// Copy from unmanged memory back to array<br />
Marshal.Copy(ptr2, buffer, 0, 10);<br />
<br />
// Free memory, or else we will leak it<br />
Marshal.FreeHGlobal(ptr);<br />
Marshal.FreeHGlobal(ptr2);<br />

// Create buffer
Int32[] buffer = new Int32[10];
buffer[5] = 1;

// Allocate and copy to unmanaged memory
IntPtr ptr = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(Int32)) * 10);
Marshal.Copy(buffer, 0, ptr, 10);

// **** Need to add this, otherwise c# complains about not being able to convert IntPtr to int
int bptr = (int)ptr;
ocx.PutData(ref bptr, Marshal.SizeOf(typeof(Int32)) * 10);

// Change buffer, so we can see that the ptr has restored the
// old value
buffer[5] = 2;

// Free memory, or else we will leak it
Marshal.FreeHGlobal(ptr);

// ... Somewhere else in code


// **** Allocate another are to retrieve data
IntPtr ptr2 = IntPtr.Zero;
int bptr2 = (int)ptr2;

ocx.GetData(ref bptr2);

// Copy from unmanged memory back to array
Marshal.Copy(ptr2, buffer, 0, 10);

IntPtr ptr = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(Int32)) * 10);
Marshal.Copy(buffer, 0, ptr, 10);
int bptr = (int)ptr;
axVecad1.PutExData(ref bptr, 10 * 4);