Re: GetIpNetTable

Tech-Archive recommends: Fix windows errors by optimizing your registry

From: James Jenkins (James_at_REMOVETHIS1STtamarsolutions.co.uk)
Date: 10/18/04 

Date: Mon, 18 Oct 2004 16:05:27 +0100

"Nicholas Paldino [.NET/C# MVP]" <mvp@spam.guard.caspershouse.com> wrote in
message news:%23RvuaqRtEHA.1452@TK2MSFTNGP11.phx.gbl...
> 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]
> - mvp@spam.guard.caspershouse.com
>
> "James Jenkins" <James@REMOVETHIS1STtamarsolutions.co.uk> wrote in message
> news:OWh%23A7ItEHA.3156@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
>>
>>
>
>

Excellent - I will take a close look at this code and hopefully learn from
it - As I have to implement many IP Helper functions - thanks again - any
more tips would be appreciated