How to tell if SQL Server automated upgrade is successful from C# WinForms app

Question

I'm automating an upgrade of SQL Server 2005 Express to SQL Server 2008R2 Express via a WinForms app that is used to upgrade our application. The application is deployed at some 800+ locations, so we don't want any manual steps.

I've got the following code mostly written to perform the upgrade. I need to know, what's best practice for determining if the SQL Server installer completed successfully? Should I just look for an exit code of 0 for the process? Is that good enough; i.e. could it still exit with code of 0 if the upgrade had a problem and was rolled back (I'd test this, but don't know the best way to simulate a failure)?

Is there any other way to determine if the upgrade was successful in my C# app, so I can handle it properly if there was any error encountered by the SQL Server Installer?

try
{

    //First, find the version of the currently installed SQL Server Instance
    string sqlString = "SELECT SUBSTRING(CONVERT(VARCHAR, SERVERPROPERTY('productversion')), 0, 5)";
    string sqlInstanceVersion = string.Empty;                

    using (DbCommand cmd = _database.GetSqlStringCommand(sqlString))
    {
        sqlInstanceVersion = cmd.ExecuteScalar().ToString();
    }

    if (sqlInstanceVersion.Equals(String.Empty))
    {
        //TODO throw an exception or do something else
    }

    //11.00 = SQL2012, 10.50 = SQL2008R2, 10.00 = SQL2008, 9.00 = SQL2005, 8.00 = SQL2000
    switch (sqlInstanceVersion)
    {
        case "11.00":
        case "10.50":
        case "10.00":
            //Log that the version is already up to date and return
            return;
        case "9.00":
        case "8.00":
            //We are on SQL 2000 or 2005, so continue with upgrade to 2008R2
            break;
        default:
            //TODO throw an exception for unsupported SQL Server version
            break;
    }

    string upgradeArgumentString = "/Q /ACTION=upgrade /INSTANCENAME={0} /ENU /IACCEPTSQLSERVERLICENSETERMS";
    string instanceName = "YourInstanceNameHere";
    string installerFilePath = AppDomain.CurrentDomain.BaseDirectory + "\\SQLEXPR_x86_ENU.exe"; 

    if (!File.Exists(installerFilePath))
    {
        throw new FileNotFoundException(string.Format("Unable to find installer file: {0}", installerFilePath));
    }

    Process process = new Process
    {
        StartInfo = { FileName = installerFilePath, Arguments = String.Format(upgradeArgumentString, instanceName), UseShellExecute = false }
    };

    process.Start();

    if (process.WaitForExit(SQLSERVER_UPGRADE_TIMEOUT))
    {
        //Do something here when the process completes within timeout.
        //What should I do here to determine if the SQL Server Installer completed successfully?  Look at just the exit code?
    }
    else
    {
        //The process exceeded timeout.  Do something about it; like throw exception, or whatever
    }
}
catch(Exception ex)
{
    //Handle your exceptions here
}

Answer 1

Look at the full version string, nut just the first 5 chars of it. A successful upgrade will change the version string.