http://www.codeproject.com/Articles/1003177/Access-bit-HKLM-Software-Registry-by-bit-Csharp-NE
While running 32-bit Windows application on a 64-bit windows OS, there is a registry redirection. Here, if 32-bit application tries to read a key under HKLM\Software, then due to Registry redirection effective path becomes HKLM\Software\Wow6432Node. For example, we are running 64-bit and 32-bit application to read registry keys as HKLM\Software\xyz and HKLM\Software\Wow6432Node\xyz.
So by default, with an input of HKLM\Software, 64-bit application will read HKLM\Software\xyz while because of registry redirection 32-bit application will read HKLM\Software\Wow6432Node\xyz.
In C#, to read 64-bit HKLM\Software registry keys, we can use RegistryKey.OpenBaseKey method. This method takes two arguments- RegistryHive and RegistryView. Here, seperate registry views are present for 32-bit and 64-bit.
Here is the sample C# code to read AppPaths for 32-bit and 64-bit applications installed on the system:
try
{
string AppPath = @"SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths";
RegistryKey rkbase = null;
rkbase = RegistryKey.OpenBaseKey
(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry32);
using (RegistryKey rk = rkbase.OpenSubKey(uninstallKey))
{
foreach (string skName in rk.GetSubKeyNames())
{
using (RegistryKey sk = rk.OpenSubKey(skName))
{
try
{ if (sk.GetValue("Path") != null)
{
//add this to required list
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
}
} if (Environment.Is64BitOperatingSystem)
{
using (RegistryKey rk = Registry.LocalMachine.OpenSubKey(AppPath))
{
foreach (string skName in rk.GetSubKeyNames())
{
using (RegistryKey sk = rk.OpenSubKey(skName))
{
try
{
if (sk.GetValue("Path") != null)
{
//add this to required list
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
}
}
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
Here, Environment.Is64BitOperatingSystem is used to check if the current system is 64-bit or not. This function is avialable with .NET Framework 4.0.