另一个进程使用的文件；PDF.JS；iText

我使用PDF.JS在画布元素中显示我上传到服务器的文档，使用的PDF.JS运行良好。那一次我使用iTextSharp对文档进行数字签名。当我试图签署文档时，会抛出一个异常(Exception.IO.Exception(该文件已被另一个进程使用。这是我上传文件的代码：(

[HttpPost]
    public async Task<JsonResult> Upload()
    {
        string fileName = null;
        try
        {
            foreach (string item in Request.Files)
            {
                var fileContent = Request.Files[item];
                if(fileContent != null && fileContent.ContentLength > 0)
                {
                    var inputStream = fileContent.InputStream;
                    fileName = fileContent.FileName;
                    string path = Path.Combine(Server.MapPath("~/UploadFolder"), fileName);
                    using (fileContent.InputStream)
                    {
                        using (var stream = new FileStream(path, FileMode.Create))
                        {
                            await inputStream.CopyToAsync(stream);
                        }
                    }
                }
            }
        }
        catch (Exception e)
        {
            return Json("Upload failed");
        }
        return Json(fileName);
    }

以下是我如何在画布中显示PDF

$(document).ready(function () {
$("#btn2").click(function () {
    var url = document.getElementById("document-to-sign").getAttribute("required-document");
    if (url != "" && url != null) {
        var pdfDoc = null,
            pageNum = 1,
            pageRendering = false,
            pageNumPending = null,
            scale = 1.5,
            canvas = document.getElementById('document-to-sign'),
            ctx = canvas.getContext('2d');
        function renderPage(num) {
            pageRendering = true;
            pdfDoc.getPage(num).then(function (page) {
                var viewport = page.getViewport(scale);
                canvas.height = viewport.height;
                canvas.width = viewport.width;
                var renderContext = {
                    canvasContext: ctx,
                    viewport: viewport
                };
                var renderTask = page.render(renderContext);
                renderTask.promise.then(function () {
                    pageRendering = false;
                    if (pageNumPending !== null) {
                        renderPage(pageNumPending);
                        pageNumPending = null;
                    }
                });
            });
            document.getElementById('page_num').textContent = pageNum;
        }
        function queueRenderPage(num) {
            if (pageRendering) {
                pageNumPending = num;
            } else {
                renderPage(num);
            }
        }
        function onPrevPage() {
            if (pageNum <= 1) {
                return;
            }
            pageNum--;
            queueRenderPage(pageNum);
        }
        document.getElementById('prev').addEventListener('click', onPrevPage);
        function onNextPage() {
            if (pageNum >= pdfDoc.numPages) {
                return;
            }
            pageNum++;
            queueRenderPage(pageNum);
        }
        document.getElementById('next').addEventListener('click', onNextPage);
        PDFJS.getDocument(url).then(function (pdfDoc_) {
            pdfDoc = pdfDoc_;
            document.getElementById('page_count').textContent = pdfDoc.numPages;
            renderPage(pageNum);
        });
        PDFJS.disableStream = true;
        $("#document-to-sign").removeAttr("required-document");
    }
});

最后，我就是这样签署文件的(添加空白字段以签署(

public static void AddField(string src, 
                                Double x1X, Double x1Y, Double x2X, Double x2Y, int page, 
                                string User)
    {
        try
        {
            PdfReader reader = new PdfReader(src);
            using (PdfStamper s = new PdfStamper(reader, new FileStream(src, FileMode.Open)))
            {
                PdfFormField field = PdfFormField.CreateSignature(s.Writer);
                field.FieldName = "Signature de " + User;
                field.SetWidget(new Rectangle(Convert.ToSingle(x1X), Convert.ToSingle(x1Y), Convert.ToSingle(x2X), Convert.ToSingle(x2Y)), PdfAnnotation.HIGHLIGHT_PUSH);
                field.Flags = PdfAnnotation.FLAGS_PRINT;
                s.AddAnnotation(field, page);
            }
        }
        catch (Exception e)
        {
            logger.Fatal(e.ToString());
            throw e;
        }
    }

我在这一行

using (PdfStamper s = new PdfStamper(reader, new FileStream(src, FileMode.Open)))

编辑：

我只是在这一步中添加siging字段。签署文档将是下一个任务，在控制台应用程序中，我用自己的证书来签署文档。上传文档，添加签名字段并对其进行签名将更进一步：(
抱歉造成混淆。

非常感谢。：(