How to merge multiple files DOCX, PDF into single document in memory using C# and .NET

  1. Add SautinSoft.Document from Nuget.
  2. Create an empty single document.
  3. Load and Import content from each document.
  4. Save the single document.

Here we'll show you how to merge: DOCX, PDF into single PDF file in memory.

Complete code

using System;
using System.IO;
using System.Collections.Generic;
using SautinSoft.Document;

namespace Sample
{
    class Sample
    {

        static void Main(string[] args)
        {
            // Get your free 30-day key here:   
            // https://sautinsoft.com/start-for-free/

            MergeDocumentsInMem();
        }

        /// <summary>
        /// This sample shows how to merge multiple files DOCX, PDF into single document in memory.
        /// </summary>
        /// <remarks>
        /// Details: https://sautinsoft.com/products/document/help/net/developer-guide/merge-multiple-documents-docx-pdf-in-memory-net-csharp-vb.php
        /// </remarks>
        public static void MergeDocumentsInMem()
        {
            // We'll use these files only to get data and show the result.
            // The whole merging process will be done in memory.
            string[] documents = new string[] { @"..\..\..\one.docx", @"..\..\..\two.pdf" };
            string singleDocumentPath = "Result.pdf";

            // Read the files and retrieve the file data into this Dictionary.
            // Thus we'll have input data completely in memory.
            Dictionary<string, byte[]> documentsData = new Dictionary<string, byte[]>();
            foreach (string file in documents)
            {
                documentsData.Add(file, File.ReadAllBytes(file));
            }

            // Merge documents in memory (using MemoryStream)
            // 1. Create a single document.
            DocumentCore dcSingle = new DocumentCore();

            foreach (KeyValuePair<string, byte[]> document in documentsData)
            {
                // Create new MemoryStream based on document byte array.
                using (MemoryStream msDoc = new MemoryStream(document.Value))
                {
                    LoadOptions lo = null;
                    if (Path.GetExtension(document.Key).ToLower() == ".docx")
                        lo = new DocxLoadOptions();
                    else if (Path.GetExtension(document.Key).ToLower() == ".pdf")
                        lo = new PdfLoadOptions() 
						{
							// 'Disabled' - Never load embedded fonts in PDF. Use the fonts with the same name installed at the system or similar by font metrics.
							// 'Enabled' - Always load embedded fonts in PDF.
							// 'Auto' - Load only embedded fonts missing in the system. In other case, use the system fonts.
							PreserveEmbeddedFonts = PropertyState.Auto 
						};

                    DocumentCore dc = DocumentCore.Load(msDoc, lo);

                    Console.WriteLine("Adding: {0}...", Path.GetFileName(document.Key));

                    // Create import session.
                    ImportSession session = new ImportSession(dc, dcSingle, StyleImportingMode.KeepSourceFormatting);

                    // Loop through all sections in the source document.
                    foreach (Section sourceSection in dc.Sections)
                    {
                        // Because we are copying a section from one document to another,
                        // it is required to import the Section into the destination document.
                        // This adjusts any document-specific references to styles, bookmarks, etc.
                        //
                        // Importing a element creates a copy of the original element, but the copy
                        // is ready to be inserted into the destination document.
                        Section importedSection = dcSingle.Import<Section>(sourceSection, true, session);

                        // First section start from new page.
                        if (dc.Sections.IndexOf(sourceSection) == 0)
                            importedSection.PageSetup.SectionStart = SectionStart.NewPage;

                        // Now the new section can be appended to the destination document.
                        dcSingle.Sections.Add(importedSection);
                    }
                }
            }

            // Save the resulting document as PDF into MemoryStream.
            using (MemoryStream msPdf = new MemoryStream())
            {
                dcSingle.Save(msPdf, new PdfSaveOptions());

                // Let's also save our document to PDF file for showing the result.
                File.WriteAllBytes(singleDocumentPath, msPdf.ToArray());

                // Open the result for demonstration purposes.
                System.Diagnostics.Process.Start(new System.Diagnostics.ProcessStartInfo(singleDocumentPath) { UseShellExecute = true });
            }
        }
    }
}

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Imports System
Imports System.IO
Imports System.Collections.Generic
Imports SautinSoft.Document

Namespace Sample
	Friend Class Sample

		Shared Sub Main(ByVal args() As String)
			MergeDocumentsInMem()
		End Sub
                ''' Get your free 30-day key here:   
                ''' https://sautinsoft.com/start-for-free/
		''' <summary>
		''' This sample shows how to merge multiple files DOCX, PDF into single document in memory.
		''' </summary>
		''' <remarks>
		''' Details: https://sautinsoft.com/products/document/help/net/developer-guide/merge-multiple-documents-docx-pdf-in-memory-net-csharp-vb.php
		''' </remarks>
		Public Shared Sub MergeDocumentsInMem()
			' We'll use these files only to get data and show the result.
			' The whole merging process will be done in memory.
			Dim documents() As String = {"..\..\..\one.docx", "..\..\..\two.pdf"}
			Dim singleDocumentPath As String = "Result.pdf"

			' Read the files and retrieve the file data into this Dictionary.
			' Thus we'll have input data completely in memory.
			Dim documentsData As New Dictionary(Of String, Byte())()
			For Each file As String In documents
				documentsData.Add(file, System.IO.File.ReadAllBytes(file))
			Next file

			' Merge documents in memory (using MemoryStream)
			' 1. Create a single document.
			Dim dcSingle As New DocumentCore()

			For Each document As KeyValuePair(Of String, Byte()) In documentsData
				' Create new MemoryStream based on document byte array.
				Using msDoc As New MemoryStream(document.Value)
					Dim lo As LoadOptions = Nothing
					If Path.GetExtension(document.Key).ToLower() = ".docx" Then
						lo = New DocxLoadOptions()
					ElseIf Path.GetExtension(document.Key).ToLower() = ".pdf" Then
						lo = New PdfLoadOptions()
					End If

					Dim dc As DocumentCore = DocumentCore.Load(msDoc, lo)

					Console.WriteLine("Adding: {0}...", Path.GetFileName(document.Key))

					' Create import session.
					Dim session As New ImportSession(dc, dcSingle, StyleImportingMode.KeepSourceFormatting)

					' Loop through all sections in the source document.
					For Each sourceSection As Section In dc.Sections
						' Because we are copying a section from one document to another,
						' it is required to import the Section into the destination document.
						' This adjusts any document-specific references to styles, bookmarks, etc.
						'
						' Importing a element creates a copy of the original element, but the copy
						' is ready to be inserted into the destination document.
						Dim importedSection As Section = dcSingle.Import(Of Section)(sourceSection, True, session)

						' First section start from new page.
						If dc.Sections.IndexOf(sourceSection) = 0 Then
							importedSection.PageSetup.SectionStart = SectionStart.NewPage
						End If

						' Now the new section can be appended to the destination document.
						dcSingle.Sections.Add(importedSection)
					Next sourceSection
				End Using
			Next document

			' Save the resulting document as PDF into MemoryStream.
			Using msPdf As New MemoryStream()
				dcSingle.Save(msPdf, New PdfSaveOptions())

				' Let's also save our document to PDF file for showing the result.
				File.WriteAllBytes(singleDocumentPath, msPdf.ToArray())

				' Open the result for demonstration purposes.
				System.Diagnostics.Process.Start(New System.Diagnostics.ProcessStartInfo(singleDocumentPath) With {.UseShellExecute = True})
			End Using
		End Sub
	End Class
End Namespace

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