test.cs

public IActionResult Validate([FromForm] IFormFile file)
{
    if (file == null)
    {
        return NotFound();
    }

    byte[] bPDF = GetBytesFromFormFile(file);
    var uploadedEnvelope = ExtractEnvelopeFromPDF(bPDF);

    if (uploadedEnvelope == null)
    {
        return NotFound();
    }

    var envelopes = LoadEnvelopesFromJson();
    var envelope = envelopes.FirstOrDefault(e => e.DocumentId == uploadedEnvelope.DocumentId);

    if (envelope != null && envelope.SignatureHash == uploadedEnvelope.SignatureHash)
    {
        return View(true);
    }

    return View(false);
}