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Create a PDF Viewer service for the TypeScript PDF Viewer

16 Feb 202624 minutes to read

The JavaScript PDF Viewer requires a server-side service to process PDF documents for rendering. This document explains how to create an ASP.NET Core Web API service that performs server-side preprocessing and operations used by the client.

This guide shows how to implement rendering, text extraction, thumbnail generation, annotation handling, and other server-side features required by the viewer.

Prerequisites

To get started with an ASP.NET Core Web API service, refer to System requirements for ASP.NET Core controls.

Set up an ASP.NET Core application with Web API for the PDF Viewer service

Follow these steps to create the PDF Viewer service

Step 1: In Visual Studio, choose File > New > Project to create a new application.

Visual Studio: New Project menu

Step 2: Select the ASP.NET Core Web Application template and click Next.

Select ASP.NET Core Web Application template

Step 3: In the Configure your new project dialog, enter a project name and click Next.

Configure project name dialog

Step 4: In the Additional information dialog, choose .NET 6.0 (Long-term Support) and click Create.

Choose .NET 6.0 in Additional information dialog

Step 5: After creating the project, add the Syncfusion.EJ2.PdfViewer.AspNet.Core dependency using the NuGet Package Manager.

Open the NuGet Package Manager and install the Syncfusion.EJ2.PdfViewer.AspNet.Core package.
Alt text

Install the Syncfusion.EJ2.PdfViewer.AspNet.Core package to the application.

Alt text

Step 6: Add an API controller to the project and name it PdfViewerController.
Add API Controller dialog

Step 7: Add the following code to the PdfViewerController.cs controller.

using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Caching.Memory;
using Newtonsoft.Json;
using Syncfusion.EJ2.PdfViewer;
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;

namespace PdfViewerWebService
{
    [Route("[controller]")]
    [ApiController]
    public class PdfViewerController : ControllerBase
    {
        private IWebHostEnvironment _hostingEnvironment;
        //Initialize the memory cache object  
        public IMemoryCache _cache;
        public PdfViewerController(IWebHostEnvironment hostingEnvironment, IMemoryCache cache)
        {
            _hostingEnvironment = hostingEnvironment;
            _cache = cache;
            Console.WriteLine("PdfViewerController initialized");
        }

        [HttpPost("Load")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/Load")]
        //Post action for Loading the PDF documents  
        public IActionResult Load([FromBody] Dictionary<string, string> jsonObject)
        {
            Console.WriteLine("Load called");
            //Initialize the PDF Viewer object with memory cache object
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            MemoryStream stream = new MemoryStream();
            object jsonResult = new object();
            if (jsonObject != null && jsonObject.ContainsKey("document"))
            {
                if (bool.Parse(jsonObject["isFileName"]))
                {
                    string documentPath = GetDocumentPath(jsonObject["document"]);
                    if (!string.IsNullOrEmpty(documentPath))
                    {
                        byte[] bytes = System.IO.File.ReadAllBytes(documentPath);
                        stream = new MemoryStream(bytes);
                    }
                    else
                    {
                        string fileName = jsonObject["document"].Split(new string[] { "://" }, StringSplitOptions.None)[0];

                        if (fileName == "http" || fileName == "https")
                        {
                            WebClient WebClient = new WebClient();
                            byte[] pdfDoc = WebClient.DownloadData(jsonObject["document"]);
                            stream = new MemoryStream(pdfDoc);
                        }

                        else
                        {
                            return this.Content(jsonObject["document"] + " is not found");
                        }
                    }
                }
                else
                {
                    byte[] bytes = Convert.FromBase64String(jsonObject["document"]);
                    stream = new MemoryStream(bytes);
                }
            }
            jsonResult = pdfviewer.Load(stream, jsonObject);
            return Content(JsonConvert.SerializeObject(jsonResult));
        }

        [AcceptVerbs("Post")]
        [HttpPost("Bookmarks")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/Bookmarks")]
        //Post action for processing the bookmarks from the PDF documents
        public IActionResult Bookmarks([FromBody] Dictionary<string, string> jsonObject)
        {
            //Initialize the PDF Viewer object with memory cache object
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            var jsonResult = pdfviewer.GetBookmarks(jsonObject);
            return Content(JsonConvert.SerializeObject(jsonResult));
        }

        [AcceptVerbs("Post")]
        [HttpPost("RenderPdfPages")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/RenderPdfPages")]
        //Post action for processing the PDF documents 
        public IActionResult RenderPdfPages([FromBody] Dictionary<string, string> jsonObject)
        {
            //Initialize the PDF Viewer object with memory cache object
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            object jsonResult = pdfviewer.GetPage(jsonObject);
            return Content(JsonConvert.SerializeObject(jsonResult));
        }

        [AcceptVerbs("Post")]
        [HttpPost("RenderPdfTexts")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/RenderPdfTexts")]
        //Post action for processing the PDF texts 
        public IActionResult RenderPdfTexts([FromBody] Dictionary<string, string> jsonObject)
        {
            //Initialize the PDF Viewer object with memory cache object
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            object jsonResult = pdfviewer.GetDocumentText(jsonObject);
            return Content(JsonConvert.SerializeObject(jsonResult));
        }

        [AcceptVerbs("Post")]
        [HttpPost("RenderThumbnailImages")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/RenderThumbnailImages")]
        //Post action for rendering the ThumbnailImages
        public IActionResult RenderThumbnailImages([FromBody] Dictionary<string, string> jsonObject)
        {
            //Initialize the PDF Viewer object with memory cache object
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            object result = pdfviewer.GetThumbnailImages(jsonObject);
            return Content(JsonConvert.SerializeObject(result));
        }
        [AcceptVerbs("Post")]
        [HttpPost("RenderAnnotationComments")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/RenderAnnotationComments")]
        //Post action for rendering the annotations
        public IActionResult RenderAnnotationComments([FromBody] Dictionary<string, string> jsonObject)
        {
            //Initialize the PDF Viewer object with memory cache object
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            object jsonResult = pdfviewer.GetAnnotationComments(jsonObject);
            return Content(JsonConvert.SerializeObject(jsonResult));
        }
        [AcceptVerbs("Post")]
        [HttpPost("ExportAnnotations")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/ExportAnnotations")]
        //Post action to export annotations
        public IActionResult ExportAnnotations([FromBody] Dictionary<string, string> jsonObject)
        {
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            string jsonResult = pdfviewer.ExportAnnotation(jsonObject);
            return Content(jsonResult);
        }
        [AcceptVerbs("Post")]
        [HttpPost("ImportAnnotations")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/ImportAnnotations")]
        //Post action to import annotations
        public IActionResult ImportAnnotations([FromBody] Dictionary<string, string> jsonObject)
        {
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            string jsonResult = string.Empty;
            object JsonResult;
            if (jsonObject != null && jsonObject.ContainsKey("fileName"))
            {
                string documentPath = GetDocumentPath(jsonObject["fileName"]);
                if (!string.IsNullOrEmpty(documentPath))
                {
                    jsonResult = System.IO.File.ReadAllText(documentPath);
                }
                else
                {
                    return this.Content(jsonObject["document"] + " is not found");
                }
            }
            else
            {
                string extension = Path.GetExtension(jsonObject["importedData"]);
                if (extension != ".xfdf")
                {
                    JsonResult = pdfviewer.ImportAnnotation(jsonObject);
                    return Content(JsonConvert.SerializeObject(JsonResult));
                }
                else
                {
                    string documentPath = GetDocumentPath(jsonObject["importedData"]);
                    if (!string.IsNullOrEmpty(documentPath))
                    {
                        byte[] bytes = System.IO.File.ReadAllBytes(documentPath);
                        jsonObject["importedData"] = Convert.ToBase64String(bytes);
                        JsonResult = pdfviewer.ImportAnnotation(jsonObject);
                        return Content(JsonConvert.SerializeObject(JsonResult));
                    }
                    else
                    {
                        return this.Content(jsonObject["document"] + " is not found");
                    }
                }
            }
            return Content(jsonResult);
        }

        [AcceptVerbs("Post")]
        [HttpPost("ExportFormFields")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/ExportFormFields")]
        public IActionResult ExportFormFields([FromBody] Dictionary<string, string> jsonObject)

        {
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            string jsonResult = pdfviewer.ExportFormFields(jsonObject);
            return Content(jsonResult);
        }

        [AcceptVerbs("Post")]
        [HttpPost("ImportFormFields")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/ImportFormFields")]
        public IActionResult ImportFormFields([FromBody] Dictionary<string, string> jsonObject)
        {
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            jsonObject["data"] = GetDocumentPath(jsonObject["data"]);
            object jsonResult = pdfviewer.ImportFormFields(jsonObject);
            return Content(JsonConvert.SerializeObject(jsonResult));
        }

        [AcceptVerbs("Post")]
        [HttpPost("Unload")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/Unload")]
        //Post action for unloading and disposing the PDF document resources 
        public IActionResult Unload([FromBody] Dictionary<string, string> jsonObject)
        {
            //Initialize the PDF Viewer object with memory cache object
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            pdfviewer.ClearCache(jsonObject);
            return this.Content("Document cache is cleared");
        }


        [HttpPost("Download")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/Download")]
        //Post action for downloading the PDF documents
        public IActionResult Download([FromBody] Dictionary<string, string> jsonObject)
        {
            //Initialize the PDF Viewer object with memory cache object
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            string documentBase = pdfviewer.GetDocumentAsBase64(jsonObject);
            return Content(documentBase);
        }

        [HttpPost("PrintImages")]
        [Microsoft.AspNetCore.Cors.EnableCors("MyPolicy")]
        [Route("[controller]/PrintImages")]
        //Post action for printing the PDF documents
        public IActionResult PrintImages([FromBody] Dictionary<string, string> jsonObject)
        {
            //Initialize the PDF Viewer object with memory cache object
            PdfRenderer pdfviewer = new PdfRenderer(_cache);
            object pageImage = pdfviewer.GetPrintImage(jsonObject);
            return Content(JsonConvert.SerializeObject(pageImage));
        }

        //Gets the path of the PDF document
        private string GetDocumentPath(string document)
        {
            string documentPath = string.Empty;
            if (!System.IO.File.Exists(document))
            {
                var path = _hostingEnvironment.ContentRootPath;
                if (System.IO.File.Exists(path + "/Data/" + document))
                    documentPath = path + "/Data/" + document;
            }
            else
            {
                documentPath = document;
            }
            Console.WriteLine(documentPath);
            return documentPath;
        }
        // GET api/values
        [HttpGet]
        public IEnumerable<string> Get()
        {
            return new string[] { "value1", "value2" };
        }

        // GET api/values/5
        [HttpGet("{id}")]
        public string Get(int id)
        {
            return "value";
        }
    }
}

Step 8: Change the launchUrl to pdfviewer (the controller name) in launchSettings.json as follows.

{
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:2270",
      "sslPort": 44396
    }
  },
  "profiles": {
    "PdfViewerWebService": {
      "commandName": "Project",
      "dotnetRunMessages": true,
      "launchBrowser": true,
      "launchUrl": "pdfviewer",
      "applicationUrl": "https://localhost:7255;http://localhost:5262",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "launchUrl": "pdfviewer",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

Step 9: Configure CORS and add Newtonsoft.Json for JSON format support

  • Browsers restrict cross-origin requests by default (same-origin policy). Cross-Origin Resource Sharing (CORS) allows specific cross-origin requests. Configure a CORS policy during application startup.
  • In ASP.NET Core 3.0 or later, System.Text.Json is the default. To use Newtonsoft.Json-based formatters and features, install Microsoft.AspNetCore.Mvc.NewtonsoftJson and configure it at startup.
using Microsoft.AspNetCore.ResponseCompression;
using Newtonsoft.Json.Serialization;

var builder = WebApplication.CreateBuilder(args);
var MyAllowSpecificOrigins = "MyPolicy";
builder.Services.AddControllers().AddNewtonsoftJson(options =>
{
    // Use the default property (Pascal) casing
    options.SerializerSettings.ContractResolver = new DefaultContractResolver();
});
builder.Services.AddCors(options =>
{
    options.AddPolicy(name: MyAllowSpecificOrigins,
                        builder => {
                            builder.AllowAnyOrigin()
                              .AllowAnyMethod()
                              .AllowAnyHeader();
                        });
});

builder.Services.AddMemoryCache();
builder.Services.AddEndpointsApiExplorer();

builder.Services.Configure<GzipCompressionProviderOptions>(options => options.Level = System.IO.Compression.CompressionLevel.Optimal);
builder.Services.AddResponseCompression();

var app = builder.Build();

//Register Syncfusion license
string licenseKey = string.Empty;
Syncfusion.Licensing.SyncfusionLicenseProvider.RegisterLicense(licenseKey);

app.UseHttpsRedirection();
app.UseCors(MyAllowSpecificOrigins);
app.UseAuthorization();

app.UseResponseCompression();
app.MapControllers();

app.Run();

Replace the empty licenseKey value with a valid Syncfusion license key before deploying this service; obtain license information from the Syncfusion account portal.

View the sample in GitHub: PDF Viewer web service sample on GitHub