data.cs

// this method stores the document hash in the blockchain
[System.Web.Http.HttpPost]
public ActionResult StoreDocument(
    [FromBody] string Document,
    [FromBody] string UniqueId,
    [FromBody] string SignerName)
{
    byte[] bPDF;

    // create temporary ServerTextControl
    using (TXTextControl.ServerTextControl tx = new TXTextControl.ServerTextControl())
    {
        tx.Create();

        // load the document
        tx.Load(Convert.FromBase64String(Document),
            TXTextControl.BinaryStreamType.InternalUnicodeFormat);

        TXTextControl.SaveSettings saveSettings = new TXTextControl.SaveSettings()
        {
            CreatorApplication = "TX Text Control Sample Application",
        };

        // save the document as PDF
        tx.Save(out bPDF, TXTextControl.BinaryStreamType.AdobePDF, saveSettings);
    }

    // calculate the MD5 checksum of the binary data
    // and store in SignedDocument object
    SignedDocument document = new SignedDocument()
    {
        Checksum = Checksum.CalculateMD5(bPDF)
    };

    // define a Blockchain object
    Blockchain bcDocument;

    // if the blockchain exists, load it
    if (System.IO.File.Exists(
        Server.MapPath("~/App_Data/Blockchains/" + UniqueId + ".bc")))
    {
        string bc = System.IO.File.ReadAllText(
            Server.MapPath("~/App_Data/Blockchains/" + UniqueId + ".bc"));

        bcDocument = JsonConvert.DeserializeObject<Blockchain>(bc);
    }
    else
        bcDocument = new Blockchain(true); // otherwise create a new blockchain

    // add a new block to the blockchain and store the SignedDocument object
    bcDocument.AddBlock(new Block(DateTime.Now, null, JsonConvert.SerializeObject(document)));

    // store the blockchain as a file
    System.IO.File.WriteAllText(
        Server.MapPath("~/App_Data/Blockchains/" + UniqueId + ".bc"),
        JsonConvert.SerializeObject(bcDocument));

    // create and return a view model with the PDF and the unique document ID
    StoredDocument storedDocument = new StoredDocument()
    {
        PDF = Convert.ToBase64String(bPDF),
        DocumentId = UniqueId
    };

    return new JsonResult() { Data = storedDocument,
        JsonRequestBehavior = JsonRequestBehavior.AllowGet };
}