Save and Load Annotations with ASP.NET

In addition to showing how to add the WebViewer component to an ASP.NET project, this sample expands on annotation functionality by enabling saving and loading the annotation objects into the local file system.

The saving and loading are done through GET and POST HTTP messages that are handled by an AnnotationController in the project. The annotations are stored as XFDF strings embedded in the messages and saved as XFDF files on disk.

WebViewer provides a slick out-of-the-box responsive UI that enables you to view, annotate and manipulate PDFs and other document types inside any web project.

Click the button below to view the full project in GitHub.

1var viewerElement = document.getElementById('viewer');
2var DOCUMENT_ID = 'webviewer-demo-1';
3
4WebViewer({
5  path: '/Scripts/webviewer/lib',
6  initialDoc: 'https://pdftron.s3.amazonaws.com/downloads/pl/demo.pdf',
7  documentXFDFRetriever: () => loadXfdfString(DOCUMENT_ID)
8}, viewerElement).then(instance => {
9  const {annotationManager} = instance.Core;
10  
11  // Add a save button on header
12  const topHeader = instance.UI.getModularHeader('default-top-header');
13  const items = topHeader.getItems();
14  
15  const saveButton = {
16    type: 'customButton',
17    img: '<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M0 0h24v24H0z" fill="none"/><path d="M17 3H5c-1.11 0-2 .9-2 2v14c0 1.1.89 2 2 2h14c1.1 0 2-.9 2-2V7l-4-4zm-5 16c-1.66 0-3-1.34-3-3s1.34-3 3-3 3 1.34 3 3-1.34 3-3 3zm3-10H5V5h10v4z"/></svg>',
18    title: 'Save Annotations',
19    onClick: function() {
20      // Save annotations when button is clicked
21      // widgets and links will remain in the document without changing so it isn't necessary to export them
22      annotationManager.exportAnnotations({ links: false, widgets: false }).then(function (xfdfString) {
23        saveXfdfString(DOCUMENT_ID, xfdfString)
24        .then(function() {
25          alert('Annotations saved successfully.');
26        })
27        .catch(function () {
28          alert('Annotations not saved successfully.');
29        });
30      });
31    }
32  };
33
34  items.push(saveButton);
35  topHeader.setItems(items);
36});
37
38// Make a POST request with XFDF string
39var saveXfdfString = function(id, xfdfString) {
40  return new Promise(function(resolve) {
41    fetch(`/api/annotation?id=${id}`, {
42      method: 'POST',
43      body: xfdfString
44    }).then(function(res) {
45      if (res.status === 200 || res.status === 204) {
46        resolve();
47      }
48    });
49  });
50};
51
52// Make a GET request to get XFDF string
53var loadXfdfString = function(id) {
54  return new Promise(function(resolve) {
55    fetch(`/api/annotation?id=${id}`, {
56      method: 'GET'
57    }).then(function(res) {
58      if (res.status === 200 || res.status === 204) {
59        res.text().then(function(xfdfString) {
60          resolve(xfdfString);
61        });
62      }
63    });
64  });
65};
66

1using System.Collections.Generic;
2using System.IO;
3using System.Net;
4using System.Net.Http;
5using System.Threading.Tasks;
6using System.Web.Http;
7
8/**
9 * AnnotationController.cs
10 * This is a sample of basic server-side annotation handling using ASP.NET.
11 * When WebViewer makes a POST request with annotations to save, this script will save the annotations to a file.
12 * When WebViewer makes a GET request to load the annotations, this script will fetch the annotations from the file and return it.
13 * Note that this is only a sample and does not take account of security and concurrency.
14 **/
15
16namespace WebApplication1.Controllers
17{
18    public class AnnotationController : ApiController
19    {
20        // Handle GET request sent to '/api/annotation'
21        // GET api/<controller>
22        public HttpResponseMessage Get()
23        {
24            string filePath = GetFilePath(this.Request);
25            if (File.Exists(filePath))
26            {
27                // Read from the XFDF file and send the string as a response
28                string xfdfData = File.ReadAllText(filePath);
29                return new HttpResponseMessage() { Content = new StringContent(xfdfData) };
30            }
31            else
32            {
33                return new HttpResponseMessage(HttpStatusCode.NoContent);
34            }
35        }
36
37        // Handle POST request sent to '/api/annotation'
38        // POST api/<controller>
39        public async Task Post()
40        {
41            string filePath = GetFilePath(this.Request);
42            string xfdfData = await Request.Content.ReadAsStringAsync();
43            File.WriteAllText(filePath, xfdfData);
44        }
45
46        private string GetFilePath(HttpRequestMessage request)
47        {
48            string id = GetId(request);
49            string fileName = (id != null) ? id : "default";
50            return System.Web.HttpContext.Current.Server.MapPath(string.Format("~\\{0}.xfdf", fileName));
51        }
52
53        private string GetId(HttpRequestMessage request)
54        {
55            var pairs = Request.GetQueryNameValuePairs();
56            string documentId = null;
57            foreach (KeyValuePair<string, string> kvp in pairs)
58            {
59                if (kvp.Key == "id")
60                {
61                    documentId = kvp.Value;
62                }
63            }
64
65            return documentId;
66        }
67    }
68}

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Save and Load Annotations with ASP.NET