Download the package "libclamox-win32" and add references to "libclamox.dll" and "libclamoxcs.dll" to your project. Your project output folder should contain Clamox libraries and folders for virus database, temporary files and quarantined files :

// Clamox init
Clamox.AgentConfig conf = new Clamox.AgentConfig(null, Clamox.Util.IsAdministrator());
String clamoxDir = Clamox.Util.getCurrentEnvPath() + "\\database";

// Database update
int resultCode = -1;
if (!Clamox.Freshclam.UpdateVirusDB(clamoxDir,conf.CurrentOptions, ref resultCode))
    throw new Exception("Error : code = "+resultCode.ToString()); 

// Print virus database stats
String version = "?";
String date = "?";
int signo = 0;
if (Clamox.Database.GetStats(clamoxDir, ref signo, ref version, ref date))
{
    Console.WriteLine("Version : " + version);
    Console.WriteLine("Date : " + date;
    Console.WriteLine("Signo : "+signo.ToString();
}
else
    throw new Exception("Database not found");

// Load Clamox configuration and init engine
conf.CurrentOptions.loadFromClamoxRegistry("default");
resultCode = -1;
if (!Clamox.ClamavEngine.InitEngine(conf, ref resultCode))
    throw new Exception("Clamav engine init failed code=" +
                          resultCode.ToString()); 

// Memory scan
String virusName = "";
String notScanned = "";
resultCode = -1;
int pid = -1;
if (Clamox.ClamavEngine.ScanProcesses(ref virusName, ref resultCode,
                                      ref pid, ref notScanned))
{
    switch (resultCode)
    {
        case Clamox.Symbols.CL_VIRUS:
            Console.WriteLine("Scanned VIRUS : " + virusName);
            break;
        case Clamox.Symbols.CL_CLEAN:
            Console.WriteLine("Scanned SAFE");
            break;
        default:
            Console.WriteLine("Scanned ERROR " + resultCode.ToString() +
                              " pid=" + pid.ToString());
            break;
    }
}
else
    throw new Exception("Memory scan ERROR " + resultCode.ToString() +
                        " pid=" + pid.ToString());

// File scan
if (Clamox.ClamavEngine.ScanFile("path_of_the_file_to_scan",
                                 ref virusName, ref resultCode))
{
    switch (resultCode)
    {
        case Clamox.Symbols.CL_VIRUS:
            Console.WriteLine("Scanned VIRUS : " + virusName);
            break;
        case Clamox.Symbols.CL_CLEAN:
            Console.WriteLine("Scanned SAFE");
            break;
        default:
            Console.WriteLine("Scanned ERROR code=" + resultCode.ToString());
            break;
    }
}
else
    throw new Exception("File scan ERROR code=" + resultCode.ToString());    

Clamox.ClamavEngine.FreeEngine();