System.NullReferenceException 中第一次偶然出现的“GetproductCode.exe”类型的异常求解,谢谢

       

 public static string GetProductCode(string displayName)

        {

            string productCode = string.Empty;

            string[] SubKeyNames;

            //string[] valueNames;

            string displayname;

            //string info;

            // 如果是32位操作系统，（或者系统是64位，程序也是64位）

            string bit32 = @"SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall";

            // 如果操作系统是64位并且程序是32位的

            string bit64 = @"SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall";

            RegistryKey localMachine = Registry.LocalMachine;

            RegistryKey Uninstall = localMachine.OpenSubKey(bit32, true);

            SubKeyNames = Uninstall.GetSubKeyNames();



            foreach (string subkey in SubKeyNames)

            {

                RegistryKey productcode = Uninstall.OpenSubKey(subkey);

                //valueNames = productcode.GetValueNames();

                //foreach (string valueName in valueNames)

                //{

                //    int i = valueName.IndexOf("DisplayName");

                //    if (i != -1)

                //    {

                //        RegistryKey myreg = Uninstall.OpenSubKey();

                //        info = myreg.GetValue(valueName).ToString();

                //        MessageBox.Show("结果的值是:" + info);

                //    }

                //}

                    displayname = productcode.GetValue("DisplayName").ToString();

                    //if (displayname == displayName)

                    if (displayname.IndexOf( displayName)!=-1)

                    {

                        MessageBox.Show(displayname);



                        string uninstallString = productcode.GetValue("UninstallString").ToString();

                        string[] strs = uninstallString.Split(new char[2] { '{', '}' });

                        productCode = strs[1];

                        return productCode;

                    }

                

            }

            return productCode;

        }