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Introduction

The sample code below shows the API's and code necessary to enumerate the servers on a domain. The ServerType enum determines the filter for the NetServerEnum call.

The tricky part (I found) was using the unsafe keyword to actually get the pointer to the array of structures, and then marshalling the pointers to strings (server names) back into managed code. I spent a couple of hours trying to get this to work...but the frustration has paid off.

The demo project contains a usercontrol that implements the NetServerEnum API. The user of the control then only has to set the ServerType property, and the drop-down will be populated.

public enum ServerTypeEnum
{
    steNone = 0,
    steWorkstation = 0x00000001,
    steAll = 0x00000002,
    steSQLServer = 0x00000004,
    steDomainController = 0x00000008
}

[sysimport(dll="netapi32.dll")]
private static extern void NetApiBufferFree([marshal(UnmanagedType.U4)]uint bufptr);

[sysimport(dll="netapi32.dll")] 
unsafe private static extern uint NetServerEnum([marshal(UnmanagedType.LPWStr)] string ServerName, 
        uint level,
        [marshal(UnmanagedType.LPVoid)]uint* bufptr,
        uint prefmaxlen,
        ref uint entriesread,
        ref uint totalentries,
        uint servertype,
        [marshal(UnmanagedType.LPWStr)] string domain, 
        uint resume_handle);

[System.Runtime.InteropServices.StructLayoutAttribute (LayoutKind.Sequential, CharSet=CharSet.Auto)]
public struct SERVER_INFO_101 
{ 
    public int dwPlatformID; 
    public int lpszServerName;
    public int dwVersionMajor; 
    public int dwVersionMinor; 
    public int dwType; 
    public int lpszComment;
}

protected void GetServers()
{
    string servername = null;
    string domain = "YourDomainName"; 
    uint level = 101, prefmaxlen = 0xFFFFFFFF, entriesread = 0, 
         totalentries = 0, resume_handle = 0; 
    
    cboServers.Items.Clear();

    unsafe
    {    
        //get a pointer to the server info structure

        SERVER_INFO_101* si = null;
        SERVER_INFO_101* pTmp;    //temp pointer for use when looping 

                                  //through returned (pointer) array


        //this api requires a pointer to a byte array...

        //which is actually a pointer to an array of SERVER_INFO_101 structures

        //If the domain parameter is NULL, the primary domain is implied. 

        uint nRes = NetServerEnum(servername, level, 
                (uint *) &si, prefmaxlen, ref entriesread, ref totalentries, 
                (uint)_ServerType, domain, resume_handle);
                
        if (nRes == 0)
        {
            if ((pTmp = si) != null)    //assign the temp pointer 

            {
                for (int i = 0; i < entriesread; i++)    //loop through the entries

                {
                    try
                    {
                        //the lpszServerName member of the structure contains a pointer to 

                        //the server name string...marshal the pointer from unmanaged

                        //memory to a managed string

                        cboServers.Items.Add(Marshal.PtrToStringAuto(pTmp->lpszServerName));
                    }
                    catch (Exception e)
                    {
                        MessageBox.Show(e.Message) ;
                    }
                    pTmp++;        // increment the pointer...essentially move to the next 

                                   // structure in the array

                }
            }
        }
        NetApiBufferFree((uint)si);
    }             
}

History

30 May 2002 - updated source files

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Databases servers Thiago Berti 5:50 22 Mar '07   Hi there, i downloaded your example, and it worked well in my project. But, since I work with MS SQL Server, IBM DB2 and Sybase, I kind of needed to be able to see those servers too. Can anybody help me with that? Thanks Thiago Berti Thomaz Sign In·View Thread·PermaLink I don't convert project... Begin Programing 17:50 7 Sep '06   Sorry all. but i'm not convert it(I'm not know) it's not run. Can u help me how use it? Thanks Sign In·View Thread·PermaLink I need Help cumhur.kose@msn.com 2:05 12 Nov '04   :(I need find SQLSERVER by this codes but I doesn't it work...help me... PS: SQLSERVER local work....and about SQLSERVER network workk....but the CoomboBox is null.... Sign In·View Thread·PermaLink Translation to VB.NET DarkKnightWI 4:11 9 Aug '04   Does anybody have a translation to VB.NET. I'm not a C# developer and do not have the time right now to learn. James M. Dorame Sign In·View Thread·PermaLink Re: Translation to VB.NET Damien Guard 7:00 4 Nov '04   You do not need to translate C# components to VB.NET and vice versa providing they use just the CLS of .Net. This component almost does, see the end for the correction. Unpack the zip to your system, and add the project file contained within it to your solution and compile. Now go to your VB WinForms project within the solution, expand references and choose this components project from the project tab. It just so happens there is a slight oversight in this component that prevents it working. Open ServerList.cs and change the line public enum ServerTypeEnum : uint to public enum ServerTypeEnum : long As uint is not supported by the CLS. [)amien Sign In·View Thread·PermaLink 2.00/5 kaaa-rist! Anonymous 12:14 3 Jun '02   you've got to be kidding me...I can do this in like ten lines of code or less. This website is really starting to suck ass. Sign In·View Thread·PermaLink 2.00/5 Re: kaaa-rist! James T. Johnson 12:54 3 Jun '02   If you can do it in 10 lines of code or less post an article about it so we can all learn. Without that article myself and others will just write you off as another anonymous coward that can't take criticism. James Simplicity Rules! Sign In·View Thread·PermaLink 5.00/5 translation to Final Visual Studio dumbatz 14:10 1 Apr '02   Has anyone a working translation of this Code. The Problem is: I can compile the Code from shillin but I get no servernames and the "entriesread" variable is 0. please help me with this Problem !! Dumbatz Sign In·View Thread·PermaLink Re: translation to Final Visual Studio Shilin 8:33 22 May '02   Hi, I only need make the following change then works fine for the Release Version 1: // public override void Dispose() // { // base.Dispose(); // components.Dispose(); // } //b2_to_v1 protected override void Dispose(bool disposing) { if (disposing) { if (components != null) { components.Dispose(); } } base.Dispose(disposing); } Regards, Shilin Sign In·View Thread·PermaLink Beta2 version of the "C# Server Drop-down Control" Shilin 8:20 22 Nov '01   Hi Marty, Thanks for your work! It's helpful for passing an array of UDTs (structures) in an unsafe way although I am still looking for the safe managed way(how to pass a safearray of   UDTs? http://www.csharphelp.com/board/read.html?num=1&id=7393&loc=0&thread=7393). I have successfully converted the beta 1 version code to beta2 version.It works great.           [DllImport("netapi32.dll", CharSet=CharSet.Auto)]           private static extern void NetApiBufferFree([MarshalAs(UnmanagedType.U4)]uint bufptr);           [DllImport("netapi32.dll", CharSet=CharSet.Auto)]           unsafe private static extern uint NetServerEnum([MarshalAs(UnmanagedType.LPWStr)] string ServerName,                                                                  uint level,                                                                  uint* bufptr,                                                                  uint prefmaxlen,                                                                  ref uint entriesread,                                                                  ref uint totalentries,                                                                  uint servertype,                                                                  [MarshalAs(UnmanagedType.LPWStr)] string domain,                                                                  uint resume_handle);           [System.Runtime.InteropServices.StructLayoutAttribute (LayoutKind.Sequential, CharSet=CharSet.Auto)]           public struct SERVER_INFO_101           {                public int dwPlatformID;                public int lpszServerName;                public int dwVersionMajor;                public int dwVersionMinor;                public int dwType;                public int lpszComment;           }           protected void GetServers()           {                string servername = null;                uint level = 101, prefmaxlen = 0xFFFFFFFF, entriesread = 0, totalentries = 0;                //uint servertype = 0x00000004,                uint resume_handle = 0;                               cboServers.Items.Clear(); ....                unsafe                {                         //get a pointer to the server info structure                     SERVER_INFO_101* si = null;                     SERVER_INFO_101* pTmp;     //temp p ointer for use when looping through returned (pointer) array                     //this api requires a pointer to a byte array...which is actually a pointer to an array                     //of SERVER_INFO_101 structures                     //If the domain parameter is NULL, the primary domain is implied.                     uint nRes = NetServerEnum(servername, level, (uint *) &si, prefmaxlen, ref entriesread, ref totalentries,                                                        (uint)_ServerType, null, resume_handle);                                         if (nRes == 0)                     {                          if ((pTmp = si) != null)                         //assign the temp pointer                          {                               for (int i = 0; i < entriesread; i++)     //loop through the entries                               {                                    try                                    {                                         //the lpszServerName member of the structure contains a pointer to                                         //the server name string...MarshalAs the pointer from unmanaged                                         //memory to a managed string                                         IntPtr intPtr = IntPtr.Zero;                                         intPtr = new IntPtr (pTmp->lpszServerName);                                         cboServers.Items.Add(Marshal.PtrToStringAuto( intPtr));                                    }                                    catch (Exception e)                                    {                                         MessageBox.Show(e.Message) ;                                    }                                    pTmp++;          //increment the pointer...essentially move to the next structure in the array                               }                          }                     }                     NetApiBufferFree((uint)si);                }                          }       } } Shilin Sign In·View Thread·PermaLink 2.00/5 Re: Beta2 version of the "C# Server Drop-down Control" rbrock0381 12:51 22 Mar '07   Plz share your version to the world. =D Start sending me a copy to rodolphobrock@gmail.com =D Thanks Sign In·View Thread·PermaLink Crazy Win32 API function call Dimon aka Manowar 7:19 2 Mar '01   Hi Has anyone explain me how I can call Win32 API function GetNetworkParams(PFIXED_INFO pFixedInfo, PULONG pOutBufLen) where PFIXED_INFO is typedef struct { char HostName[MAX_HOSTNAME_LEN + 4] ; char DomainName[MAX_DOMAIN_NAME_LEN + 4]; PIP_ADDR_STRING CurrentDnsServer; IP_ADDR_STRING DnsServerList; UINT NodeType; char ScopeId[MAX_SCOPE_ID_LEN + 4]; UINT EnableRouting; UINT EnableProxy; UINT EnableDns; } FIXED_INFO, *PFIXED_INFO; and PIP_ADDR_STRING is typedef struct _IP_ADDR_STRING { struct _IP_ADDR_STRING* Next; IP_ADDRESS_STRING IpAddress; IP_MASK_STRING IpMask; DWORD Context; } IP_ADDR_STRING, *PIP_ADDR_STRING; I can't (or I can't understand how to) declare correct structures PFIXED_INFO and PIP_ADDR_STRING. Best regards, Dimon Sign In·View Thread·PermaLink 1.67/5

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