Check if SQL Server is installed on a machine through C#

You've got several ways to do it:

• SmoApplication.EnumAvailableSqlServers()
• SqlDataSourceEnumerator.Instance
• Direct access to system registry

Direct access isn't the recommended solution by MS, because they can change keys/paths. But the other solutions are not robust and fails providing instances on 64-bit platforms.

Therefore I prefer to check SQL Server instances in System Registry. Doing that, keep in mind the difference in Registry access between x86 and x64 platforms. Windows 64-bit stores data in different parts of system registry and combines them into views. So using RegistryView is essential.

using Microsoft.Win32;

RegistryView registryView = Environment.Is64BitOperatingSystem ? RegistryView.Registry64 : RegistryView.Registry32;
using (RegistryKey hklm = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, registryView))
{
    RegistryKey instanceKey = hklm.OpenSubKey(@"SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL", false);
    if (instanceKey != null)
    {
        foreach (var instanceName in instanceKey.GetValueNames())
        {
            Console.WriteLine(Environment.MachineName + @"\" + instanceName);
        }
    }
}

If you are looking for 32-bit instances on a 64-bit OS (pretty weird, but possible), you will need to look:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Microsoft SQL Server

If your app is installed on the machine in question, you could inspect the registry using something similar to this:

using Microsoft.Win32; 
RegistryKey RK = Registry.CurrentUser.OpenSubKey(@"SOFTWARE\MICROSOFT\Microsoft SQL Server");
    if(RK != null)
    {
       // It's there 
    }
    else
    {
       // It's not there 
    }