场景：正常使用的一段程序，最近出现有获取不到mac地址的机器，导致登录不了我们的系统

问题寻找：找到注册表下的mac address,发现在以太网的适配器下并不能找到mac address。如：计算机型号：HUAWEI MACH-WX9

分析及解决方案：一般计算机存在两个mac地址，一个是无线网卡的mac地址，一个是有线网卡的mac地址

此类型的计算机没有以太网适配器，只存在无线网卡，所以返回值总是空值，添加判定条件为找不到有线mac地址时去获取无线mac地址

原程序代码：

public string GetMacAddressByNetworkInformation()
        {
            string key = "SYSTEM\\CurrentControlSet\\Control\\Network\\{4D36E972-E325-11CE-BFC1-08002BE10318}\\";
            string macAddress = string.Empty;
            try
            {
                NetworkInterface[] nics = NetworkInterface.GetAllNetworkInterfaces();
                foreach (NetworkInterface adapter in nics)
                {
                    if (adapter.NetworkInterfaceType == NetworkInterfaceType.Ethernet
                        && adapter.GetPhysicalAddress().ToString().Length != 0)
                    {
                        string fRegistryKey = key + adapter.Id + "\\Connection";
                        RegistryKey rk = Registry.LocalMachine.OpenSubKey(fRegistryKey, false);
                        if (rk != null)
                        {
                            string fPnpInstanceID = rk.GetValue("PnpInstanceID", "").ToString();
                            //int fMediaSubType = Convert.ToInt32(rk.GetValue("MediaSubType", 0));
                            if (fPnpInstanceID.Length > 3 && fPnpInstanceID.Substring(0, 3) == "PCI")
                            {
                                macAddress = adapter.GetPhysicalAddress().ToString();
                                break;
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                string str = ex.Message;
            }
            return macAddress;
        }

修改后

public string GetMacAddressByNetworkInformation()
        {
            string key = "SYSTEM\\CurrentControlSet\\Control\\Network\\{4D36E972-E325-11CE-BFC1-08002BE10318}\\";
            string macAddress = string.Empty;
            try
            {
                NetworkInterface[] nics = NetworkInterface.GetAllNetworkInterfaces();
                foreach (NetworkInterface adapter in nics)
                {
                    if (adapter.NetworkInterfaceType == NetworkInterfaceType.Ethernet
                        && adapter.GetPhysicalAddress().ToString().Length != 0)
                    {
                        string fRegistryKey = key + adapter.Id + "\\Connection";
                        RegistryKey rk = Registry.LocalMachine.OpenSubKey(fRegistryKey, false);
                        if (rk != null)
                        {
                            string fPnpInstanceID = rk.GetValue("PnpInstanceID", "").ToString();
                            //int fMediaSubType = Convert.ToInt32(rk.GetValue("MediaSubType", 0));
                            if (fPnpInstanceID.Length > 3 && fPnpInstanceID.Substring(0, 3) == "PCI")
                            {
                                macAddress = adapter.GetPhysicalAddress().ToString();
                                break;
                            }
                        }
                    }
                }
                if (string.IsNullOrEmpty(macAddress))
                {
                    foreach (NetworkInterface adapter in nics)
                    {
                        if (adapter.NetworkInterfaceType == NetworkInterfaceType.Wireless80211
                            && adapter.GetPhysicalAddress().ToString().Length != 0)
                        {
                            string fRegistryKey = key + adapter.Id + "\\Connection";
                            RegistryKey rk = Registry.LocalMachine.OpenSubKey(fRegistryKey, false);
                            if (rk != null)
                            {
                                string fPnpInstanceID = rk.GetValue("PnpInstanceID", "").ToString();
                                //int fMediaSubType = Convert.ToInt32(rk.GetValue("MediaSubType", 0));
                                if (fPnpInstanceID.Length > 3 && fPnpInstanceID.Substring(0, 3) == "PCI")
                                {
                                    macAddress = adapter.GetPhysicalAddress().ToString();
                                    break;
                                }
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                string str = ex.Message;
            }
            return macAddress;
        }

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