c#调用API显示内部局域网内的主机

//写这个程序,为了是显示局域网内的主机,然后通过用户点击选中的机器,检查是否该主机上安装有sqlserver,是为一个配置程序所写的
//这里提供code,给有需要的朋友

//设置dll必须使用该命名空间
using system.runtime.interopservices;

  #region 动态链接库定义
  [dllimport("mpr.dll",charset=charset.auto)] private static extern int wnetenumresource(intptr henum, ref int lpccount,intptr lpbuffer, ref int lpbuffersize );
  [dllimport("mpr.dll",charset=charset.auto)] private static extern int wnetopenenum(resource_scope dwscope,resource_type dwtype,resource_usage dwusage,[marshalas(unmanagedtype.asany)][in] object lpnetresource,out intptr lphenum);
  [dllimport("mpr.dll",charset=charset.auto)] private static extern int wnetcloseenum( intptr henum );
  #endregion

  #region 定义枚举常量
  public enum resource_scope
  {
   resource_connected = 0x00000001,
   resource_globalnet = 0x00000002,
   resource_remembered = 0x00000003,
   resource_recent= 0x00000004,
   resource_context= 0x00000005
  }

  public enum resource_type
  {
   resourcetype_any= 0x00000000,
   resourcetype_disk= 0x00000001,
   resourcetype_print = 0x00000002,
   resourcetype_reserved = 0x00000008,
  }

  public enum resource_usage
  {
   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 resource_displaytype
  {
   resourcedisplaytype_generic= 0x00000000,
   resourcedisplaytype_domain= 0x00000001,
   resourcedisplaytype_server= 0x00000002,

   resourcedisplaytype_share= 0x00000003,
   resourcedisplaytype_file = 0x00000004,
   resourcedisplaytype_group= 0x00000005,
   resourcedisplaytype_network= 0x00000006,
   resourcedisplaytype_root = 0x00000007,
   resourcedisplaytype_shareadmin = 0x00000008,
   resourcedisplaytype_directory = 0x00000009,
   resourcedisplaytype_tree = 0x0000000a,
   resourcedisplaytype_ndscontainer = 0x0000000b
  }

  public struct netresource
  {
   public resource_scope dwscope;
   public resource_type dwtype;
   public resource_displaytype dwdisplaytype;
   public resource_usage dwusage;
   [marshalas(system.runtime.interopservices.unmanagedtype.lptstr)] public string lplocalname;
   [marshalas(system.runtime.interopservices.unmanagedtype.lptstr)] public string lpremotename;
   [marshalas(system.runtime.interopservices.unmanagedtype.lptstr)] public string lpcomment;
   [marshalas(system.runtime.interopservices.unmanagedtype.lptstr)] public string lpprovider;
  }

  public enum nerr
  {
   nerr_success = 0,/* success */
   error_more_data = 234, // dderror
   error_no_browser_servers_found = 6118,
   error_invalid_level = 124,
   error_access_denied = 5,
   error_invalid_parameter = 87,
   error_not_enough_memory = 8,
   error_network_busy = 54,
   error_bad_netpath = 53,
   error_no_network = 1222,
   error_invalid_handle_state = 1609,
   error_extended_error= 1208
  }
  #endregion

  #region 开始列举网络函数
  public treenode pnode1;
  public treenode pnode2;
  public treenode pnode3;
  private void wnetoe(object o)
  {
   int iret;
   intptr ptrhandle = new intptr();
   try
   {
    iret =wnetopenenum(resource_scope.resource_globalnet,resource_type.resourcetype_any,resource_usage.resourceusage_all,o,out ptrhandle );
    if( iret != 0 )return;

    int entries;
    int buffer = 16384;
    intptr ptrbuffer = marshal.allochglobal(buffer);
    netresource nr;
    
    for(;;)
    {
     entries = -1;
     buffer = 16384;
     iret =wnetenumresource(ptrhandle,ref entries,ptrbuffer,ref buffer);
     if((iret != 0) || (entries<1))break;

     int32 ptr = ptrbuffer.toint32();
     for(int i=0;i<entries;i++ )
     {
      nr = (netresource)marshal.ptrtostructure( new intptr(ptr), typeof(netresource) );
      if(resource_usage.resourceusage_container == (nr.dwusage & resource_usage.resourceusage_container))
      {
       
       ptr += marshal.sizeof( nr );
       if(nr.dwdisplaytype == resource_displaytype.resourcedisplaytype_network)
       {
        pnode1 = tview.nodes.add(nr.lpremotename);//treeview
        pnode1.imageindex = 0;
        pnode1.selectedimageindex = 0;
       }
       else if(nr.dwdisplaytype == resource_displaytype.resourcedisplaytype_domain)
       {
        pnode2 = pnode1.nodes.add(nr.lpremotename);
        pnode2.imageindex = 1;
        pnode2.selectedimageindex =1;
       }
       else if(nr.dwdisplaytype == resource_displaytype.resourcedisplaytype_server)
       {
        string spcname = nr.lpremotename;
        pnode3 = pnode2.nodes.add(spcname.substring(2,spcname.length-2));//此处为去处机器名称前的两个"//"字符
        pnode3.imageindex = 2;
        pnode3.selectedimageindex = 2;
       }

       wnetoe(nr);
      }
      
     }
    }
    marshal.freehglobal( ptrbuffer );
    iret =wnetcloseenum( ptrhandle );
   }
   catch(exception ex)
   {
    messagebox.show("查找本地网络错误:"+ex.message,"错误",messageboxbuttons.ok,messageboxicon.error);
   }
  }

  #endregion

  //窗体load事件中,使用函数
  private void frmdbconnconfig_load(object sender, system.eventargs e)
  {
   wnetoe(null);
  }