C# 服务器下拉列表控件

下载源代码文件 - 6 Kb

下载演示项目 - 7 Kb

引言

以下示例代码展示了枚举域中服务器所需的 API 和代码。ServerType 枚举确定 NetServerEnum 调用的筛选器。

棘手的部分（我发现）是使用 unsafe 关键字来实际获取结构体数组的指针，然后将指针编组回托管代码中的字符串（服务器名称）。我花了几个小时才让它工作...但这种挫败感是值得的。

演示项目包含一个用户控件，该控件实现了 NetServerEnum API。控件的用户只需要设置 ServerType 属性，下拉菜单就会被填充。

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);
    }             
}

历史

2002年5月30日 - 更新了源文件