C# Exception reading registry: Null reference exception

Question

I'm trying to develop a method to read the programs installed on the machine.

public void refreshProgramsFromWindows () {
            string SoftwareKey = "SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Installer\\UserData\\S-1-5-18\\Products";
            RegistryKey rk = default(RegistryKey);
            rk = Registry.LocalMachine.OpenSubKey(SoftwareKey);
            //string skname = null;
            string sname = string.Empty;

            // New list from scratch
            this.installedSoftwareList = new List<software>();

            // Object software info
            software aSoftware = new software();

            foreach (string skname in rk.GetSubKeyNames())
            {

                // Reset software info
                aSoftware.reset();

                try
                {
                    // Name of the programm
                    sname = Registry.LocalMachine.OpenSubKey(SoftwareKey).OpenSubKey(skname).OpenSubKey("InstallProperties").GetValue("DisplayName").ToString();
                    aSoftware.name = sname;

                    // Write program to the list
                    installedSoftwareList.Add(aSoftware);
                }
                catch (Exception ex)
                {

                }
            }

Net Framework is 4.5 and i'm over Windows 7/8. When i debug this piece of code var rk is null, and it's throwing a null reference exception in the foreach. The app manifest is set to require admin Privileges, so the registry is readable. What is the problem?

Thanks you in advance. Cheers.

http://stackoverflow.com/questions/1268715/registry-localmachine-opensubkey-returns-null — OldProgrammer, Apr 22 '13 at 02:19

score 4 · Accepted Answer · answered Apr 22 '13 at 02:35

64 bits registry problem:

Added (to handle 64 bit registry):

public static RegistryKey GetRegistryKey()
        {
            return GetRegistryKey(null);
        }

        public static RegistryKey GetRegistryKey(string keyPath)
        {
            RegistryKey localMachineRegistry
                = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine,
                                          Environment.Is64BitOperatingSystem
                                              ? RegistryView.Registry64
                                              : RegistryView.Registry32);

            return string.IsNullOrEmpty(keyPath)
                ? localMachineRegistry
                : localMachineRegistry.OpenSubKey(keyPath);
        }

        public static object GetRegistryValue(string keyPath, string keyName)
        {
            RegistryKey registry = GetRegistryKey(keyPath);
            return registry.GetValue(keyName);
        }

And changed:

rk = Registry.LocalMachine.OpenSubKey(SoftwareKey);

to

rk = GetRegistryKey(SoftwareKey);

And now it works.

C# Exception reading registry: Null reference exception

1 Answers1