test.cs

[HttpPost]
public IActionResult Sign([FromBody] SignatureData data, string signerId) {

DocumentFlow flow = new DocumentFlow(data.UniqueId);
   Signer signer = flow.Signers.Find(x => x.Id == signerId);

   signer.SignatureComplete = true;

   flow.Save();

   byte[] imageData = Convert.FromBase64String(data.SignatureImage);
   System.IO.File.WriteAllBytes("App_Data/documentflows/" + flow.EnvelopeId + "/signature_" + signer.Id + ".svg", imageData);

   bool allSigned = flow.Signers.All(y => y.SignatureComplete == true);

   if (allSigned == true) {

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

         // load the signed document
         tx.Load("App_Data/documentflows/" + flow.EnvelopeId + "/template.tx", TXTextControl.StreamType.InternalUnicodeFormat);

         List<TXTextControl.DigitalSignature> digitalSignatures = new List<DigitalSignature>();

         foreach (SignatureField field in tx.SignatureFields) {
            signer = flow.Signers.Find(x => x.SignatureFieldName == field.Name);
            field.Image = new SignatureImage("App_Data/documentflows/" + flow.EnvelopeId + "/signature_" + signer.Id + ".svg", 4);
            field.SignerData = new SignerData(signer.Name, "", "", "", "Text Control Signature Demo");

            // provide unique field name
            field.Name = field.Name + "_" + Guid.NewGuid().ToString();

            digitalSignatures.Add(new DigitalSignature(
               new System.Security.Cryptography.X509Certificates.X509Certificate2(
                  "App_Data/textcontrolself.pfx", "123"), null, field.Name));
          }

         SaveSettings saveSettings = new SaveSettings() {
            SignatureFields = digitalSignatures.ToArray()
         };

         tx.Save("App_Data/documentflows/" + flow.EnvelopeId + "/results.pdf", TXTextControl.StreamType.AdobePDF, saveSettings);

         flow.Closed = true;
         flow.Save();
      }
   }

   return Ok();
}