Merge or combine multiple WinForms Excel files in C#, VB.NET.

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Syncfusion® Excel (XlsIO) library is a .NET Excel library used to create, read, and edit Excel documents. Using this library, you can split one Excel file into multiple files or combine several Excel files into a single file in C# and VB.NET.

Steps to merge or combine multiple Excel files into a single Excel file programmatically:

Step 1: Create a new C# console application project.

Create Console application in Visual Studio

Create a new C# console application

Step 2: Install Syncfusion.XlsIO.WinForms NuGet package as a reference to your .NET Framework applications from the NuGet.org.

Add XlsIO reference to the project

Install NuGet package

Step 3: Include the following namespaces in the Program.cs file:

using Syncfusion.XlsIO;
using System.IO;
using System.Reflection;

VB.NET

Imports Syncfusion.XlsIO
Imports System.IO
Imports System.Reflection

Step 4: Add the following code snippet to merge or combine multiple Excel files into single Excel file.

// Initialize ExcelEngine
using (ExcelEngine excelEngine = new ExcelEngine())
{
    // Initialize Application
    IApplication application = excelEngine.Excel;
 
    // Set default application version
    application.DefaultVersion = ExcelVersion.Excel2013;
 
    // Open existing workbooks with data entered
    Assembly assembly = typeof(Program).GetTypeInfo().Assembly;
 
    Stream fileStream1 = assembly.GetManifestResourceStream("MergeExcelFiles.Owner.xlsx");
    IWorkbook workbook1 = application.Workbooks.Open(fileStream1);
    IWorksheet worksheet = workbook1.Worksheets[0];
 
    Stream fileStream2 = assembly.GetManifestResourceStream("MergeExcelFiles.Sales Manager.xlsx");
    IWorkbook workbook2 = application.Workbooks.Open(fileStream2);
 
    Stream fileStream3 = assembly.GetManifestResourceStream("MergeExcelFiles.Sales Representative.xlsx");
    IWorkbook workbook3 = application.Workbooks.Open(fileStream3);
 
    // The content in the range A1:C8 from workbook2 and workbook3 is copied to workbook1
    int lastRow = worksheet.UsedRange.LastRow;
    workbook2.Worksheets[0].UsedRange.CopyTo(worksheet.Range[lastRow + 1, 1]);
 
    lastRow = worksheet.UsedRange.LastRow;
    workbook3.Worksheets[0].UsedRange.CopyTo(worksheet.Range[lastRow + 1, 1]);
 
    worksheet.UsedRange.AutofitColumns();
 
    // Save the workbook
    workbook1.SaveAs("Output.xlsx");
}

VB.NET

'Initialize ExcelEngine
Using excelEngine As ExcelEngine = New ExcelEngine()
 
  'Initialize Application
  Dim application As IApplication = excelEngine.Excel
 
  'Set default application version
  application.DefaultVersion = ExcelVersion.Excel2013
 
  'Open existing workbooks with data entered
  Dim assembly As Assembly = GetType(Program).GetTypeInfo.Assembly
 
  Dim fileStream1 As Stream = assembly.GetManifestResourceStream("MergeExcelFiles.Owner.xlsx")
  Dim workbook1 As IWorkbook = application.Workbooks.Open(fileStream1)
  Dim worksheet As IWorksheet = workbook1.Worksheets(0)
 
  Dim fileStream2 As Stream = assembly.GetManifestResourceStream("MergeExcelFiles.Sales Manager.xlsx")
  Dim workbook2 As IWorkbook = application.Workbooks.Open(fileStream2)
 
  Dim fileStream3 As Stream = assembly.GetManifestResourceStream("MergeExcelFiles.Sales Representative.xlsx")
  Dim workbook3 As IWorkbook = application.Workbooks.Open(fileStream3)
 
  'The content in the range A1:C8 from workbook2 and workbook3 is copied to workbook1
  Dim lastRow As Integer = worksheet.UsedRange.LastRow
  workbook2.Worksheets(0).UsedRange.CopyTo(worksheet.Range((lastRow + 1), 1))
 
  lastRow = worksheet.UsedRange.LastRow
  workbook3.Worksheets(0).UsedRange.CopyTo(worksheet.Range((lastRow + 1), 1))
 
  worksheet.UsedRange.AutofitColumns()
 
  'Save the workbook
  workbook1.SaveAs("Output.xlsx")
 
End Using

A complete working example to merge or combine multiple Excel files along with the input files used can be downloaded from Merge Excel files.zip.

CopyTo() method copies the range to the specified destination range. CopyTo() method has four overloads to merge or combine multiple Excel files whose API references are as follows:

CopyTo(IRange)
CopyTo(IRange,ExcelCopyRangeOptions)
CopyTo(IRange,Boolean)
CopyTo(IRange,ExcelCopyRangeOptions,Boolean)

The input files used in this sample look like:

Merge or Combine Excel Files

Input file

By executing the program, you will get the output Excel file as shown below.

Merge or Combine Excel Files

Output Excel document

Take a moment to peruse the documentation where you can find basic Excel document processing options along with the features like import and export data, chart, formulas, conditional formatting, data validation, tables, pivot tables and protect the Excel documents, and most importantly, the PDF, CSV and Image conversions with code examples.

Refer here to explore the rich set of Syncfusion® Excel (XlsIO) library features.

Merge or combine multiple WinForms Excel files in C#, VB.NET.

Steps to merge or combine multiple Excel files into a single Excel file programmatically:

See Also:

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