Enumerating Network Resources

using System;
using System.Collections;
using System.Runtime.InteropServices;

namespace ServerEnumerator
{
    /// <summary>
    /// The ServerEnum class is used to enumerate servers on the
    /// network.
    /// </summary>
    ///
	public enum ResourceScope
	{
		RESOURCE_CONNECTED = 1,
		RESOURCE_GLOBALNET,
		RESOURCE_REMEMBERED,
		RESOURCE_RECENT,
		RESOURCE_CONTEXT
	};

	public enum ResourceType
	{
		RESOURCETYPE_ANY,
		RESOURCETYPE_DISK,
		RESOURCETYPE_PRINT,
		RESOURCETYPE_RESERVED
	};

	public enum ResourceUsage
	{
		RESOURCEUSAGE_CONNECTABLE   = 0x00000001,
		RESOURCEUSAGE_CONTAINER     = 0x00000002,
		RESOURCEUSAGE_NOLOCALDEVICE = 0x00000004,
		RESOURCEUSAGE_SIBLING       = 0x00000008,
		RESOURCEUSAGE_ATTACHED      = 0x00000010,
		RESOURCEUSAGE_ALL           = (RESOURCEUSAGE_CONNECTABLE | RESOURCEUSAGE_CONTAINER | RESOURCEUSAGE_ATTACHED),
	};
	
	public enum ResourceDisplayType
	{
		RESOURCEDISPLAYTYPE_GENERIC,
		RESOURCEDISPLAYTYPE_DOMAIN,
		RESOURCEDISPLAYTYPE_SERVER,
		RESOURCEDISPLAYTYPE_SHARE,
		RESOURCEDISPLAYTYPE_FILE,
		RESOURCEDISPLAYTYPE_GROUP,
		RESOURCEDISPLAYTYPE_NETWORK,
		RESOURCEDISPLAYTYPE_ROOT,
		RESOURCEDISPLAYTYPE_SHAREADMIN,
		RESOURCEDISPLAYTYPE_DIRECTORY,
		RESOURCEDISPLAYTYPE_TREE,
		RESOURCEDISPLAYTYPE_NDSCONTAINER
	};

    public class ServerEnum : IEnumerable
    {
        enum ErrorCodes
        {
            NO_ERROR = 0,
            ERROR_NO_MORE_ITEMS = 259
        };

        [StructLayout(LayoutKind.Sequential)]
        private class NETRESOURCE 
        {
            public ResourceScope       dwScope = 0;
            public ResourceType        dwType = 0;
            public ResourceDisplayType dwDisplayType = 0;
            public ResourceUsage       dwUsage = 0;
            public string              lpLocalName = null;
            public string              lpRemoteName = null;
            public string              lpComment = null;
            public string              lpProvider = null;
        };

        private ArrayList aData = new ArrayList();

        public int Count
        {
            get { return aData.Count; }
        }

        [DllImport("Mpr.dll", EntryPoint="WNetOpenEnumA", CallingConvention=CallingConvention.Winapi)]
        private static extern ErrorCodes WNetOpenEnum(ResourceScope dwScope, ResourceType dwType, ResourceUsage dwUsage, NETRESOURCE p, out IntPtr lphEnum);

        [DllImport("Mpr.dll", EntryPoint="WNetCloseEnum", CallingConvention=CallingConvention.Winapi)]
        private static extern ErrorCodes WNetCloseEnum(IntPtr hEnum);

        [DllImport("Mpr.dll", EntryPoint="WNetEnumResourceA", CallingConvention=CallingConvention.Winapi)]
        private static extern ErrorCodes WNetEnumResource(IntPtr hEnum, ref uint lpcCount, IntPtr buffer, ref uint lpBufferSize);

		private	void EnumerateServers(NETRESOURCE pRsrc, ResourceScope scope, ResourceType type, ResourceUsage usage, ResourceDisplayType displayType)
		{
			uint		bufferSize = 16384;
			IntPtr		buffer	= Marshal.AllocHGlobal((int) bufferSize);
			IntPtr		handle = IntPtr.Zero;
			ErrorCodes	result;
			uint		cEntries = 1;

			result = WNetOpenEnum(scope, type, usage, pRsrc, out handle);

			if (result == ErrorCodes.NO_ERROR)
			{
				do
				{
					result = WNetEnumResource(handle, ref cEntries,	buffer,	ref	bufferSize);

					if (result == ErrorCodes.NO_ERROR)
					{
						Marshal.PtrToStructure(buffer, pRsrc);

						if (pRsrc.dwDisplayType	== displayType)
							aData.Add(pRsrc.lpRemoteName);

						if ((pRsrc.dwUsage & ResourceUsage.RESOURCEUSAGE_CONTAINER)	== ResourceUsage.RESOURCEUSAGE_CONTAINER)
							EnumerateServers(pRsrc,	scope, type, usage,	displayType);
					}
					else if	(result	!= ErrorCodes.ERROR_NO_MORE_ITEMS)
						break;
				} while	(result	!= ErrorCodes.ERROR_NO_MORE_ITEMS);

				WNetCloseEnum(handle);
			}

			Marshal.FreeHGlobal((IntPtr) buffer);
		}

		public ServerEnum(ResourceScope scope, ResourceType type, ResourceUsage usage, ResourceDisplayType displayType)
		{
			NETRESOURCE pRsrc = new NETRESOURCE();

			EnumerateServers(pRsrc, scope, type, usage, displayType);
		}
		#region IEnumerable Members

		public IEnumerator GetEnumerator()
		{
			return aData.GetEnumerator();
		}

		#endregion
	}
}