iText7 pdf 到 blob c#

Question

Using c# and iText7 I need to modify an existing PDF and save it to blob storage. I have a console app that does exactly what I need using the file system:

        PdfReader reader = new PdfReader(source);
        PdfWriter writer = new PdfWriter(destination2);
        PdfDocument pdfDoc = new PdfDocument(reader, writer);
        PdfAcroForm form = PdfAcroForm.GetAcroForm(pdfDoc, true);
        fields = form.GetFormFields();

        fields.TryGetValue("header", out PdfFormField cl);
        var type = cl.GetType();
        cl.SetValue("This is a header");
        pdfDoc.Close();

This works just fine. However I can not figure out how to do the same thing pulling the PDF from blob storage and sending the new one to blob storage

            IDictionary<string, PdfFormField> fields;
            MemoryStream outStream = new MemoryStream();
            var pdfTemplate = _blobStorageService.GetBlob("mycontainer", "TestPDF.pdf");
            PdfReader reader = new PdfReader(pdfTemplate);
            PdfWriter writer = new PdfWriter(outStream);
            PdfDocument pdfDoc = new PdfDocument(reader, writer);
            PdfAcroForm form = PdfAcroForm.GetAcroForm(pdfDoc, true);
            fields = form.GetFormFields();

            fields.TryGetValue("header", out PdfFormField cl);

            cl.SetValue("This is a header");
            pdfDoc.Close();
            outStream.Position = 0;
            _blobStorageService.UploadBlobAsync("mycontainer", **THIS IS THE ISSUE**, "newpdf.pdf");

I think I need to get pdfDoc as a byte array. Outstream is incorrect, it is only has a length of 15

Answer 1

The code below shows how to read a PDF from a file into a byte[] and also how to modify a PDF that's stored as a byte[].

Download and install NuGet package: iText7

• In Solution Explorer, right-click <project name> and select Manage NuGet Packages...
• Click Browse
• In the search box type: iText7
• Select iText7
• Select desired version
• Click Install

Add the following using statements:

using System.IO;
using iText.Kernel.Pdf;
using iText.Forms;
using iText.Forms.Fields;

Get PDF as byte[] (GetPdfBytes):

public static Task<byte[]> GetPdfBytes(string pdfFilename)
{
    byte[] pdfBytes = null;

    using (PdfReader reader = new PdfReader(pdfFilename))
    {
        using (MemoryStream msPdfWriter = new MemoryStream())
        {
            using (PdfWriter writer = new PdfWriter(msPdfWriter))
            {
                using (PdfDocument pdfDoc = new PdfDocument(reader, writer))
                {
                    //don't close underlying streams when PdfDocument is closed
                    pdfDoc.SetCloseReader(false);
                    pdfDoc.SetCloseWriter(false);

                    //close
                    pdfDoc.Close();

                    //set value
                    msPdfWriter.Position = 0;

                    //convert to byte[]
                    pdfBytes = msPdfWriter.ToArray();
                }
            }
        }
    }

    return Task.FromResult(pdfBytes);
}

Usage :

byte[] pdfBytes = null;
string filename = string.Empty;

OpenFileDialog ofd = new OpenFileDialog();
ofd.Filter = "PDF File (*.pdf)|*.pdf";

if (ofd.ShowDialog() == DialogResult.OK)
{
    //get PDF as byte[]
    var tResult = GetPdfBytes(ofd.FileName);
    pdfBytes = tResult.Result;

    //For testing, write back to file so we can ensure that the PDF file opens properly
    //create a new filename
    filename = System.IO.Path.GetFileNameWithoutExtension(ofd.FileName) + " - Test.pdf";
    filename = System.IO.Path.Combine(System.IO.Path.GetDirectoryName(ofd.FileName), filename);

    //save to file
    File.WriteAllBytes(filename, pdfBytes);
    System.Diagnostics.Debug.WriteLine("Saved as '" + filename + "'");

}

Modify PDF that's stored in a byte[] (ModifyPdf)

public static Task<byte[]> ModifyPdf(byte[] pdfBytes)
{
    byte[] modifiedPdfBytes = null;

    using (MemoryStream ms = new MemoryStream(pdfBytes))
    {
        using (PdfReader reader = new PdfReader(ms))
        {
            using (MemoryStream msPdfWriter = new MemoryStream())
            {
                using (PdfWriter writer = new PdfWriter(msPdfWriter))
                {
                    using (PdfDocument pdfDoc = new PdfDocument(reader, writer))
                    {
                        //don't close underlying streams when PdfDocument is closed
                        pdfDoc.SetCloseReader(false);
                        pdfDoc.SetCloseWriter(false);

                        //get AcroForm from document
                        PdfAcroForm form = PdfAcroForm.GetAcroForm(pdfDoc, true);

                        //get form fields
                        IDictionary<string, PdfFormField> fields = form.GetFormFields();

                        //for testing, show all fields
                        foreach (KeyValuePair<string, PdfFormField> kvp in fields)
                        {
                            System.Diagnostics.Debug.WriteLine("Key: '" + kvp.Key + "' Value: '" + kvp.Value + "'");
                        }

                        PdfFormField cl = null;

                        //get specified field
                        fields.TryGetValue("1 Employee name", out cl);

                        //set value for specified field
                        cl.SetValue("John Doe");

                        //close PdfDocument
                        pdfDoc.Close();

                        //set value
                        msPdfWriter.Position = 0;

                        //convert to byte[]
                        modifiedPdfBytes = msPdfWriter.ToArray();
                    }
                }
            }
        }
    }

    return Task.FromResult(modifiedPdfBytes);
}

Usage :

byte[] pdfBytes = null;
string filename = string.Empty;

OpenFileDialog ofd = new OpenFileDialog();
ofd.Filter = "PDF File (*.pdf)|*.pdf";

if (ofd.ShowDialog() == DialogResult.OK)
{
    //get PDF as byte[]
    var tResult = GetPdfBytes(ofd.FileName);
    pdfBytes = tResult.Result;

    //modify PDF
    pdfBytes = await ModifyPdf(pdfBytes);

    //create a new filename
    filename = System.IO.Path.GetFileNameWithoutExtension(ofd.FileName) + " - TestModified.pdf";
    filename = System.IO.Path.Combine(System.IO.Path.GetDirectoryName(ofd.FileName), filename);

    //save to file
    File.WriteAllBytes(filename, pdfBytes);
    System.Diagnostics.Debug.WriteLine("Saved as '" + filename + "'");
}

---

The code below is adapted from Sample01b_HelloWorldAsync.cs and is untested.

Download and install NuGet package: Azure.Storage.Blobs

Add the following using statement:

using Azure.Storage.Blobs;

DownloadPdf :

public static async Task<byte[]> DownloadPdf(string connectionString, string blobContainerName, string blobName)
{
    byte[] pdfBytes = null;
 
    using (MemoryStream ms = new MemoryStream())
    {
        // Get a reference to the container and then create it
        BlobContainerClient container = new BlobContainerClient(connectionString, blobContainerName);
        Azure.Response<Azure.Storage.Blobs.Models.BlobContainerInfo> responseCA = await container.CreateAsync();

        // Get a reference to the blob
        BlobClient blob = container.GetBlobClient(blobName);

        // Download the blob's contents and save it to a file
        Azure.Response responseDTA = await blob.DownloadToAsync(ms);

        //set value
        ms.Position = 0;

        //convert to byte[]
        pdfBytes = ms.ToArray();
    }

    return pdfBytes;
}

UploadPdf :

public static async Task<Azure.Response<Azure.Storage.Blobs.Models.BlobContentInfo>> UpdloadPdf(byte[] pdfBytes, string connectionString, string blobContainerName, string blobName)
{
    Azure.Response<Azure.Storage.Blobs.Models.BlobContentInfo> result = null;

    using (MemoryStream ms = new MemoryStream(pdfBytes))
    {
        //this statement may not be necessary
        ms.Position = 0; 

        // Get a reference to the container and then create it
        BlobContainerClient container = new BlobContainerClient(connectionString, blobContainerName);
        await container.CreateAsync();

        // Get a reference to the blob
        BlobClient blob = container.GetBlobClient(blobName);

        //upload
        result = await blob.UploadAsync(ms);
    }

    return result;
}

Here's a PDF file for testing .