James,
Here is how I would do it:
using System;
using System.Runtime.InteropServices;
using System.ComponentModel;
namespace ConsoleApplication5
{
class Program
{
// The max number of physical addresses.
const int MAXLEN_PHYSADDR = 8;
// Define the MIB_IPNETROW structure.
[StructLayout(LayoutKind.Sequential)]
struct MIB_IPNETROW
{
[MarshalAs(UnmanagedType.U4)]
public int dwIndex;
[MarshalAs(UnmanagedType.U4)]
public int dwPhysAddrLen;
[MarshalAs(UnmanagedType.ByValArray, SizeConst =
MAXLEN_PHYSADDR)]
byte[] bPhysAddr;
[MarshalAs(UnmanagedType.U4)]
public int dwAddr;
[MarshalAs(UnmanagedType.U4)]
public int dwType;
}
// Declare the GetIpNetTable function.
[DllImport("IpHlpApi.dll")]
[return: MarshalAs(UnmanagedType.U4)]
static extern int GetIpNetTable(
IntPtr pIpNetTable,
[MarshalAs(UnmanagedType.U4)]
ref int pdwSize,
bool bOrder);
// The insufficient buffer error.
const int ERROR_INSUFFICIENT_BUFFER = 122;
static void Main(string[] args)
{
// The number of bytes needed.
int bytesNeeded = 0;
// The result from the API call.
int result = GetIpNetTable(IntPtr.Zero, ref bytesNeeded, false);
// Call the function, expecting an insufficient buffer.
if (result != ERROR_INSUFFICIENT_BUFFER)
{
// Throw an exception.
throw new Win32Exception(result);
}
// Allocate the memory, do it in a try/finally block, to ensure
// that it is released.
IntPtr buffer = IntPtr.Zero;
// Try/finally.
try
{
// Allocate the memory.
buffer = Marshal.AllocCoTaskMem(bytesNeeded);
// Make the call again. If it did not succeed, then
// raise an error.
result = GetIpNetTable(buffer, ref bytesNeeded, false);
// If the result is not 0 (no error), then throw an
exception.
if (result != 0)
{
// Throw an exception.
throw new Win32Exception(result);
}
// Now we have the buffer, we have to marshal it. We can
read
// the first 4 bytes to get the length of the buffer.
int entries = Marshal.ReadInt32(buffer);
// Increment the memory pointer by the size of the int.
IntPtr currentBuffer = new IntPtr(buffer.ToInt64() +
sizeof(int));
// Allocate an array of entries.
MIB_IPNETROW[] table = new MIB_IPNETROW[entries];
// Cycle through the entries.
for (int index = 0; index < entries; index++)
{
// Call PtrToStructure, getting the structure
information.
table[index] = (MIB_IPNETROW) Marshal.PtrToStructure(new
IntPtr(currentBuffer.ToInt64() + (index *
Marshal.SizeOf(typeof(MIB_IPNETROW)))), typeof(MIB_IPNETROW));
}
}
finally
{
// Release the memory.
Marshal.FreeCoTaskMem(buffer);
}
}
}
}
Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
-
mv*@spam.guard.caspershouse.com
"James Jenkins" <Ja***@REMOVETHIS1STtamarsolutions.co.uk> wrote in message
news:OW****************@TK2MSFTNGP12.phx.gbl...
does anyone know how to implement the following? - I am very new to using
Marshalling and could really do with some help - it's late and I am
tired - I have spent all day on this and the net comes up with very little
help - I have followed lots of tutorials and looked at many peoples
source - I am in need of enlightenment ;) - thanks
[DllImport("iphlpapi.dll", EntryPoint="GetIpNetTable", SetLastError=true)]
public static extern int GetIpNetTable(IntPtr buffer,ref int Size, bool
Order);
I have got this far in the calling it- as below
IntPtr lpBuffer = IntPtr.Zero;
int size = 0;
int result = IPHelperAPI.GetIpNetTable(lpBuffer,ref size,true);
if(result != NO_ERROR)
{
Debug.WriteLine("NO ERROR");
lpBuffer = Marshal.AllocHGlobal(size);
result = IPHelperAPI.GetIpNetTable(lpBuffer,ref size,true);
if(result != NO_ERROR)
{
Marshal.FreeHGlobal(lpBuffer);
lpBuffer = IntPtr.Zero;
Debug.WriteLine("RETURN ERROR");
return;
}
Debug.WriteLine("I GOT THIS FAR");
// But canot allocate the structures from here - I hope someone out there
can pointer me in the right direction - good night all;;;
JJ
