[c#] Reading a registry key in C#

I have developed an application and installed it on a client computer. In my application I need to get its installation path. My application has a registry entry at:

HKEY_LOCAL_MACHINE\SOFTWARE\MyApplication\[AppPath]

How can I read AppPath using C#?

You're looking for the cunningly named Registry.GetValue method.

using Microsoft.Win32;

  string chkRegVC = "NO";
   private void checkReg_vcredist() {

        string regKey = @"SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall";
        using (Microsoft.Win32.RegistryKey uninstallKey = Registry.LocalMachine.OpenSubKey(regKey))
        {
            if (uninstallKey != null)
            {
                string[] productKeys = uninstallKey.GetSubKeyNames();
                foreach (var keyName in productKeys)
                {

                    if (keyName == "{196BB40D-1578-3D01-B289-BEFC77A11A1E}" ||//Visual C++ 2010 Redistributable Package (x86) 
                        keyName == "{DA5E371C-6333-3D8A-93A4-6FD5B20BCC6E}" ||//Visual C++ 2010 Redistributable Package (x64) 
                        keyName == "{C1A35166-4301-38E9-BA67-02823AD72A1B}" ||//Visual C++ 2010 Redistributable Package (ia64) 
                        keyName == "{F0C3E5D1-1ADE-321E-8167-68EF0DE699A5}" ||//Visual C++ 2010 SP1 Redistributable Package (x86) 
                        keyName == "{1D8E6291-B0D5-35EC-8441-6616F567A0F7}" ||//Visual C++ 2010 SP1 Redistributable Package (x64) 
                        keyName == "{88C73C1C-2DE5-3B01-AFB8-B46EF4AB41CD}"   //Visual C++ 2010 SP1 Redistributable Package (ia64) 
                        ) { chkRegVC = "OK"; break; }
                    else { chkRegVC = "NO"; }
                }
            }
        }
    }

If you want it casted to a specific type you can use this method. Most non primitive types won't by default support direct casting so you will have to handle those accordingly.

  public T GetValue<T>(string registryKeyPath, string value, T defaultValue = default(T))
  {
    T retVal = default(T);

      retVal = (T)Registry.GetValue(registryKeyPath, value, defaultValue);

      return retVal;
  }

string InstallPath = (string)Registry.GetValue(@"HKEY_LOCAL_MACHINE\SOFTWARE\MyApplication\AppPath", "Installed", null);    
if (InstallPath != null)
{
    // Do stuff
}

That code should get your value. You'll need to be

using Microsoft.Win32;

for that to work though.

You can use the following to get where the registry thinks it's installed:

(string)Registry.LocalMachine.GetValue(@"SOFTWARE\MyApplication\AppPath",
   "Installed", null);

Or you can use the following to find out where the application is actually being launched from:

System.Windows.Forms.Application.StartupPath

The latter is more reliable than the former if you're trying to use the .exe location as a relative path to find related files. The user could easily move things around after the install and still have the app work fine because .NET apps aren't so dependent upon the registry.

Using StartupPath, you could even do something clever like have your app update the registry entries at run time instead of crashing miserably due to missing/wrong/corrupted entries.

And be sure to look at the app settings functionality as storage for values rather than the registry (Properties.Settings.Default.mySettingEtc). You can read/write settings for the app and/or the user levels that get saved as simple MyApp.exe.config files in standard locations. A nice blast from the past (good old Win 3.1/DOS days) to have the application install/delete be a simple copy/delete of a folder structure or two rather than some convoluted, arcane install/uninstall routine that leaves all kinds of garbage in the registry and sprinkled all over the hard drive.