引用SQL DMO组件
//取得本局域网内所有可用sql服务器名
            cmbServer.Items.Clear();
            try
            {
                SQLDMO.Application app = new SQLDMO.ApplicationClass();
                SQLDMO.NameList list = app.ListAvailableSQLServers();
                int iCount = list.Count;
           
                for(int i = 0; i < iCount; i ++)
                {
                    string sTemp = list.Item(i);
                    if(sTemp != null)
                        cmbServer.Items.Add(sTemp);
                }
            }
            catch
            {
                //如果取得SQLDMO组件出错, 则默认把本机名写进去
                MessageBox.Show("无法取得服务器列表，可能是缺少SDLDMO.DLL！");
                cmbServer.Items.Add(System.Net.Dns.GetHostName());
            }
如果用“http://xml.sz.luohuedu.net/xml/ShowDetail.asp?id=BCEAADFB-CFF3-4804-B3B3-6C7D6488982B”里的例子也不行会出现以下信息：
"未处理的“System.InvalidCastException”类型的异常出现在WindowsApplication1.exe 中
其他信息：接口 SQLDMO.NameList 的 QueryInterface 失败。
怎么回事，请高手帮帮忙啊！
第一，你的sql server 版本不够。
 如果要使用SQLDMO.DLL就要去下载SQL sp2.
 第二，如果你想列出局域网内的所有的SQl server
 建议你用Sql server自带的 isql.exe 这个文件只要是sql server 6.5以上就可以了
 下面是源码:
  string fileName = "C:\\Program Files\\Microsoft SQL Server\\80\\Tools\\Binn\\isql.exe";
            if(System.IO.File.Exists(fileName))
            {
                System.Diagnostics.ProcessStartInfo processStartInfo = new System.Diagnostics.ProcessStartInfo(fileName,"-L");
                processStartInfo.UseShellExecute = false;
                processStartInfo.CreateNoWindow = true;
                processStartInfo.RedirectStandardOutput = true;
                processStartInfo.RedirectStandardError = true;
                System.Diagnostics.Process process = System.Diagnostics.Process.Start(processStartInfo);
                process.WaitForExit();
                cboServerList.Items.Clear();
                int line = 1;
                string server = null;
                while(process.StandardOutput.Peek() > -1)
                {
                    server = process.StandardOutput.ReadLine().Trim();
                    line +=1;
                    if ( line > 6)
                    {
                        cboServerList.Items.Add(server);
                    }
                    server = null;
                }
            }
            cboServerList.Items.Remove(System.Environment.MachineName);
            cboServerList.Items.Add("localhost");
 cboServerList是一个ComoBox

你可以现在cmd中输入isql.exe -？ 看看参数序列中有没有你想要的
 至于说列出局域网内的sql server 要输入 isql -L就可以了
private void cmbDatabase_Enter(object sender, System.EventArgs e)
        {
            //取得某服务器上的各个表名
           
            string strServer = cmbServer.Text;
            string strUid = txtUid.Text;
            if(strServer.Trim() != "" && strUid.Trim() != "")
            {
                string strPwd = txtPwd.Text;
                string strConn = "server=" + strServer + ";database=master;uid=" + strUid + ";pwd=" + strPwd;
                SqlConnection conn = null;
                try
                {
                    conn = new SqlConnection(strConn);
                    string strSQL = "select * from sysdatabases order by dbid";
                    SqlDataAdapter cmd = new SqlDataAdapter(strSQL, conn);
                    DataSet ds = new DataSet();
                    cmd.Fill(ds, "Databases");
                    cmbDatabase.Items.Clear();
                    for(int i = 0; i < ds.Tables["Databases"].Rows.Count; i ++)
                    {
                        string strDb = ds.Tables["Databases"].Rows[i]["name"].ToString();
                        cmbDatabase.Items.Add(strDb);
                    }
                }
                catch(Exception ex)
                {
                    MessageBox.Show(ex.ToString());
                }
                finally
                {
                    if(conn.State == ConnectionState.Open)
                        conn.Close();
                }
            }
            this.Cursor = Cursors.Default;
        }