Server Actions in ASP.NET MVC PDF Viewer

31 Oct 202520 minutes to read

Syncfusion^® PDF Viewer is a client-server control that processes PDF documents on the server and sends incremental responses to the client for rendering and interaction. Ensure the ASP.NET MVC controller routes are registered, dependency injection supplies IHostingEnvironment and IMemoryCache, and caching is configured to persist page data between requests. Validate file paths and restrict inputs to trusted locations to avoid exposing sensitive files.

The server actions exposed by the PDF Viewer controller include:

• Load
• RenderPdfPages
• RenderThumbnailImages
• Bookmarks
• RenderAnnotationComments
• Unload
• ExportAnnotations
• ImportAnnotations
• ImportFormFields
• ExportFormFields
• Download
• PrintImages

Load action

NOTE

public ActionResult Load(jsonObjects jsonObject)

The Load action initiates PDF loading. The PDF Viewer caches the document using the supplied hash ID, streaming the first 100 pages and fetching the remainder on demand through virtual loading. The jsonObject payload must include either a file name or base64 content, and the controller should resolve the document path by calling GetDocumentPath. The action invokes the Load API, returning serialized JSON to the viewer.

[System.Web.Mvc.HttpPost]
public ActionResult Load(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    MemoryStream stream = new MemoryStream();
    var jsonData = JsonConverter(jsonObject);
    object jsonResult = new object();
    if (jsonObject != null && jsonData.ContainsKey("document"))
    {
        if (bool.Parse(jsonData["isFileName"]))
        {
            string documentPath = GetDocumentPath(jsonData["document"]);

            if (!string.IsNullOrEmpty(documentPath))
            {
                byte[] bytes = System.IO.File.ReadAllBytes(documentPath);
                stream = new MemoryStream(bytes);

            }
            else
            {
                string fileName = jsonData["document"].Split(new string[] { "://" }, StringSplitOptions.None)[0];
                if (fileName == "http" || fileName == "https")
                {
                    var WebClient = new WebClient();
                    byte[] pdfDoc = WebClient.DownloadData(jsonData["document"]);
                    stream = new MemoryStream(pdfDoc);
                }
                else
                {
                    return this.Content(jsonData["document"] + " is not found");
                }

            }
        }
        else
        {
            byte[] bytes = Convert.FromBase64String(jsonData["document"]);
            stream = new MemoryStream(bytes);

        }
    }
    jsonResult = pdfviewer.Load(stream, jsonData);
    return Content(JsonConvert.SerializeObject(jsonResult));
}

RenderPdfPages

NOTE

public ActionResult RenderPdfPages(jsonObjects jsonObject)

Whenever the client requests a new page segment, the RenderPdfPages action retrieves the necessary bitmap information. The request payload contains the page index and size constraints. The action calls GetPage and returns the serialized page data to the viewer for incremental rendering.

[System.Web.Mvc.HttpPost]
public ActionResult RenderPdfPages(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    object jsonResult = pdfviewer.GetPage(jsonData);
    return Content(JsonConvert.SerializeObject(jsonResult));
}

RenderThumbnailImages action

NOTE

public ActionResult RenderThumbnailImages(jsonObjects jsonObject)

The RenderThumbnailImages action generates thumbnail previews for page navigation. The viewer requests thumbnails once during initialization and whenever documents change. The action invokes GetThumbnailImages to return the encoded image list that populates the thumbnail pane.

[System.Web.Mvc.HttpPost]
public ActionResult RenderThumbnailImages(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    object result = pdfviewer.GetThumbnailImages(jsonData);
    return Content(JsonConvert.SerializeObject(result));
}

Bookmarks

NOTE

public ActionResult Bookmarks(jsonObjects jsonObject)

The Bookmarks action extracts document outlines during initialization to populate the bookmarks panel. The action calls GetBookmarks and returns a hierarchical JSON structure that links bookmark selections to their corresponding page indices.

[System.Web.Mvc.HttpPost]
public ActionResult Bookmarks(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    object jsonResult = pdfviewer.GetBookmarks(jsonData);
    return Content(JsonConvert.SerializeObject(jsonResult));
}

RenderAnnotationComments

NOTE

public ActionResult RenderAnnotationComments(jsonObjects jsonObject)

The RenderAnnotationComments action synchronizes annotation discussions. It calls GetAnnotationComments to retrieve comment threads and metadata, enabling the client to display the comments panel with the latest entries.

[System.Web.Mvc.HttpPost]
public ActionResult RenderAnnotationComments(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    object jsonResult = pdfviewer.GetAnnotationComments(jsonData);
    return Content(JsonConvert.SerializeObject(jsonResult));
}

Unload action

NOTE

public ActionResult Unload(jsonObjects jsonObject)

The Unload action clears cached artifacts when the viewer closes or refreshes. Callers do not need additional payload details beyond the document GUID. The action invokes ClearCache to release memory for the stored document.

[System.Web.Mvc.HttpPost]
public ActionResult Unload(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    pdfviewer.ClearCache(jsonData);
    return this.Content("Document cache is cleared");
}

ExportAnnotations action

NOTE

public ActionResult ExportAnnotations(jsonObjects jsonObject)

The ExportAnnotations action responds to the “Export annotation to JSON” and “Export annotation to XFDF” toolbar commands. The jsonObject parameter identifies the format. The action delegates to ExportAnnotation and returns the exported data so the client can trigger a download.

[System.Web.Mvc.HttpPost]
public ActionResult ExportAnnotations(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    string jsonResult = pdfviewer.ExportAnnotation(jsonData);
    return Content((jsonResult));
}

ImportAnnotations

NOTE

public ActionResult ImportAnnotations(jsonObjects jsonObject)

The ImportAnnotations action imports XFDF or JSON annotation data supplied by the toolbar. The payload either provides a file name that resolves through GetDocumentPath or contains base64 data. Update error responses to echo available keys such as fileName to keep diagnostics consistent when documents are missing. The action ultimately calls ImportAnnotation and returns the serialized result.

[System.Web.Mvc.HttpPost]
public ActionResult ImportAnnotations(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    string jsonResult = string.Empty;
    var jsonData = JsonConverter(jsonObject);
    if (jsonObject != null && jsonData.ContainsKey("fileName"))
    {
        string documentPath = GetDocumentPath(jsonData["fileName"]);
        if (!string.IsNullOrEmpty(documentPath))
        {
            jsonResult = System.IO.File.ReadAllText(documentPath);
        }
        else
        {
            return this.Content(jsonData["document"] + " is not found");
        }
    }
    return Content(JsonConvert.SerializeObject(jsonResult));
}

ImportFormFields action

NOTE

public ActionResult ImportFormFields(jsonObjects jsonObject)

The ImportFormFields action hydrates form fields from JSON data supplied by the viewer or a stored file. The controller should resolve the source path and ensure the input is sanitized before calling ImportFormFields to populate the form fields within the loaded document.

[System.Web.Mvc.HttpPost]
public ActionResult ImportFormFields(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    object jsonResult = pdfviewer.ImportFormFields(jsonData);
    return Content(JsonConvert.SerializeObject(jsonResult));
}

ExportFormFields action

NOTE

public ActionResult ExportFormFields(jsonObjects jsonObject)

The ExportFormFields action runs when end users submit PDF forms. It serializes the current form values to JSON for custom processing or download. The action delegates to ExportFormFields and returns the generated JSON string to the viewer.

[System.Web.Mvc.HttpPost]
public ActionResult ExportFormFields(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    string jsonResult = pdfviewer.ExportFormFields(jsonData);
    return Content(jsonResult);
}

Download action

NOTE

public ActionResult Download(jsonObjects jsonObject)

The Download action streams the current PDF to the client when the toolbar download command is used. The controller calls GetDocumentAsBase64, and the client decodes the base64 string to initiate a file download.

[System.Web.Mvc.HttpPost]
public ActionResult Download(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    string documentBase = pdfviewer.GetDocumentAsBase64(jsonData);
    return Content(documentBase);
}

PrintImages

NOTE

public ActionResult PrintImages(jsonObjects jsonObject)

The PrintImages action supports client-side printing. The viewer requests each page image sequentially, and the controller calls GetPrintImage to return serialized image data that the browser uses to compose printable markup.

[System.Web.Mvc.HttpPost]
public ActionResult PrintImages(jsonObjects jsonObject)
{
    PdfRenderer pdfviewer = new PdfRenderer();
    var jsonData = JsonConverter(jsonObject);
    object pageImage = pdfviewer.GetPrintImage(jsonData);
    return Content(JsonConvert.SerializeObject(pageImage));
}

Other methods

GetDocumentPath

NOTE

private string GetDocumentPath(string document)

GetDocumentPath resolves the document file system path used by multiple actions. Ensure the implementation restricts file access to known directories and logs attempts to access missing resources for diagnostics.

private string GetDocumentPath(string document)
{
    string documentPath = string.Empty;
    if (!System.IO.File.Exists(document))
    {
        var path = HttpContext.Request.PhysicalApplicationPath;
        if (System.IO.File.Exists(path + "/App_Data/" + document))
            documentPath = path + "/App_Data/" + document;
    }
    else
    {
        documentPath = document;
    }
    return documentPath;
}

JsonConverter method

NOTE

public Dictionary<string, string> JsonConverter(jsonObjects results)

The JsonConverter method converts the posted jsonObjects instance into a flat Dictionary<string, string> for easy consumption by controller actions.

NOTE

Required namespaces: System.Reflection and System.Linq.

public Dictionary<string, string> JsonConverter(jsonObjects results)
{
    Dictionary<string, object> resultObjects = new Dictionary<string, object>();
    resultObjects = results.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public).ToDictionary(prop => prop.Name, prop => prop.GetValue(results, null));
    var emptyObjects = (from kv in resultObjects
                        where kv.Value != null
                        select kv).ToDictionary(kv => kv.Key, kv => kv.Value);
    Dictionary<string, string> jsonResult = emptyObjects.ToDictionary(k => k.Key, k => k.Value.ToString());
    return jsonResult;
}

GetPlainText method

NOTE

private HttpResponseMessage GetPlainText(string pageImage)

Use GetPlainText to return the action result status as HttpResponseMessage with text/plain content, preventing the browser from downloading a file. This pattern is helpful when actions produce data that should not trigger a download (for example, status or debug output).

private HttpResponseMessage GetPlainText(string pageImage)
{
    var responseText = new HttpResponseMessage(HttpStatusCode.OK);
    responseText.Content = new StringContent(pageImage, System.Text.Encoding.UTF8, "text/plain");
    return responseText;
}

jsonObjects class

The jsonObjects parameter represents the request payload sent by the PDF Viewer. It groups properties used across different actions; each action reads only the fields it requires. Define this class in the PDF Viewer controller so all actions can bind to it.

 public class jsonObjects
    {
        public string document { get; set; }
        public string password { get; set; }
        public string zoomFactor { get; set; }
        public string isFileName { get; set; }
        public string xCoordinate { get; set; }
        public string yCoordinate { get; set; }
        public string pageNumber { get; set; }
        public string documentId { get; set; }
        public string hashId { get; set; }
        public string sizeX { get; set; }
        public string sizeY { get; set; }
        public string startPage { get; set; }
        public string endPage { get; set; }
        public string stampAnnotations { get; set; }
        public string textMarkupAnnotations { get; set; }
        public string stickyNotesAnnotation { get; set; }
        public string shapeAnnotations { get; set; }
        public string measureShapeAnnotations { get; set; }
        public string action { get; set; }
        public string pageStartIndex { get; set; }
        public string pageEndIndex { get; set; }
        public string fileName { get; set; }
        public string elementId { get; set; }
        public string pdfAnnotation { get; set; }
        public string importPageList { get; set; }
        public string uniqueId { get; set; }
        public string data { get; set; }
        public string viewPortWidth { get; set; }
        public string viewportHeight { get; set; }
        public string tilecount { get; set; }
        public string freeTextAnnotation { get; set; }
        public string signatureData { get; set; }
        public string fieldsData { get; set; }
        public string formDesigner { get; set; }
        public string inkSignatureData { get; set; }
        public string tileXCount { get; set; }
        public string tileYCount { get; set; }
        public string digitalSignaturePageList { get; set; }
        public string annotationCollection { get; set; }
        public string annotationsPageList { get; set; }
        public string formFieldsPageList { get; set; }
        public string documentLiveCount { get; set; }
        public string annotationDataFormat { get; set; }
		public bool isCompletePageSizeNotReceived { get; set; }
        public bool hideEmptyDigitalSignatureFields { get; set; }
        public bool showDigitalSignatureAppearance { get; set; }
        public bool digitalSignaturePresent { get; set; }
		public bool isAnnotationsExist { get; set; }
        public bool isFormFieldAnnotationsExist { get; set; }
    }