Determining if ASP.Net is properly registered

First I would try running aspnet_regiis -lv. This should give you an output like:

1.1.4322.0      Valid           C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\aspnet_isapi.dll2.0.50727.0     Valid           c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll

that you can easily parse to verify that your target version is installed and valid. If it is not, you'll have to go the aspnet_regiis -i route.

Also, given that you can do this check in C#, you could add a test page to your ASP.NET application. After what you would normally consider a successful installation, do a HttpWebRequest on that test page. The page itself can be as simple as an empty page and as complicated as running a self-check of the installation (file/folder permissions, DB configuration, etc.) and would only return a HTTP 200 if everything is ok. Any timeout or error indicates a bad install. Then,optionally, delete the test page.

This snippet works for IIS7+

using Microsoft.Web.Administration;   private static string[] ARR_STR_SUPPORTED_APP_POOLS =                          { "ASP.NET v4.0", "ASP.NET v4.5", ".NET v4.5", ".NET v4.0" };public static ApplicationPool GetFirstSupportedAppPoolInstalled(this ServerManager mgr, IEnumerable<string> supportedAppPools){    ApplicationPool result = null;    foreach (string appPoolName in supportedAppPools)    {        result = mgr.ApplicationPools[appPoolName];        if (result != null)            break;    }    return result;}...using (var mgr = new ServerManager()){   if (!mgr.IISAccessCheck())      throw new ApplicationException("Error trying to access IIS 7!");   ApplicationPool appPool = mgr.GetFirstSupportedAppPoolInstalled(ARR_STR_SUPPORTED_APP_POOLS);   if (appPool == null)       throw new ApplicationException("No appropriate .NET application pool found!");   // you can do something with the app pool, if needed}...

You can adjust it as you want.