DigitalSignature.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Java.IO;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using System.IO;
using Syncfusion.Pdf.Parsing;
using System.Threading.Tasks;

using Syncfusion.Pdf;
using System.Reflection;
using Syncfusion.Pdf.Security;
using Syncfusion.Drawing;
using AndroidX.Core.Content;

namespace SampleBrowser
{
    public partial class DigitalSignature : SamplePage
    {
        private Context m_context;
        public override View GetSampleContent(Context con)
        {
            LinearLayout linear = new LinearLayout(con);
            linear.SetBackgroundColor(Android.Graphics.Color.White);
            linear.Orientation = Orientation.Vertical;
            linear.SetPadding(10, 10, 10, 10);          

            TextView space = new TextView(con);
            space.TextSize = 10;
            linear.AddView(space);

            TextView text2 = new TextView(con);
            text2.TextSize = 17;
            text2.TextAlignment = TextAlignment.Center;
            text2.Text = "This sample demonstrates how a PDF document can be secured with certificates and signed with either standard or author signatures. Now added the support for Elliptic Curve Digital Signature Algorithm (ECDSA) to sign the PDF document.";
            text2.SetTextColor(Android.Graphics.Color.ParseColor("#262626"));
            text2.SetPadding(5, 5, 5, 5);

            linear.AddView(text2);

            TextView space1 = new TextView(con);
            space1.TextSize = 10;
            linear.AddView(space1);
 
            m_context = con;

            TextView space2 = new TextView(con);
            space2.TextSize = 10;
            linear.AddView(space2);

            Button button1 = new Button(con);
            button1.Text = "Sign and Email";
            button1.Click += OnButtonClicked;
            linear.AddView(button1);

            return linear;
        }
        void OnButtonClicked(object sender, EventArgs e)
        {
            //Get the stream from the document.
            Stream docStream = typeof(Booklet).GetTypeInfo().Assembly.GetManifestResourceStream("SampleBrowser.Samples.PDF.Assets.SalesOrderDetail.pdf");
            
            //Load the PDF document into the loaded document object.
            PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

            //Get the certificate stream from .pfx file.
            Stream certificateStream = typeof(DigitalSignature).GetTypeInfo().Assembly.GetManifestResourceStream("SampleBrowser.Samples.PDF.Assets.PDF.pfx");

            //Create PdfCertificate using certificate stream and password.
            PdfCertificate pdfCert = new PdfCertificate(certificateStream, "syncfusion");

            //Add certificate to document first page.
            PdfSignature signature = new PdfSignature(loadedDocument, loadedDocument.Pages[0], pdfCert, "Signature");

            signature.Bounds = new RectangleF(5, 5, 300, 300);

            MemoryStream stream = new MemoryStream();

            //Save the PDF document
            loadedDocument.Save(stream);

            //Close the PDF document
            loadedDocument.Close(true);            
          

            if (stream != null)
            {
			   stream.Position=0;
               ComposeMail("DigitalSignature.pdf", null, "Signing the document", "Syncfusion", stream);

            }
        }
		
		  public void ComposeMail(string fileName, string[] recipients, string subject, string messagebody, MemoryStream filestream)
        {
            string exception = string.Empty;
            string root = null;
            if (Android.OS.Environment.IsExternalStorageEmulated)
            {
                root = Android.OS.Environment.ExternalStorageDirectory.ToString();
            }
            else
                root = System.Environment.GetFolderPath(System.Environment.SpecialFolder.MyDocuments);

            Java.IO.File myDir = new Java.IO.File(root + "/Syncfusion");
            myDir.Mkdir();

            Java.IO.File file = new Java.IO.File(myDir, fileName);

            if (file.Exists()) file.Delete();

            try
            {
                FileOutputStream outs = new FileOutputStream(file);
                outs.Write(filestream.ToArray());

                outs.Flush();
                outs.Close();
            }
            catch (Exception e)
            {
                exception = e.ToString();
            }

            Intent email = new Intent(Android.Content.Intent.ActionSend);
            var uri = FileProvider.GetUriForFile(this.m_context, Application.Context.PackageName + ".provider", file);

            //file.SetReadable(true, true);
            email.PutExtra(Android.Content.Intent.ExtraSubject, subject);
            email.PutExtra(Intent.ExtraStream, uri);
            email.SetType("application/pdf");

            MainActivity.BaseActivity.StartActivity(email);
        }
    }
}