How to write to existing Excel in C#, VB.NET?

Syncfusion® Excel (XlsIO) library is a .NET Excel library used to create, read, and edit Excel documents. Using this library, you can write data into an existing Excel worksheet in C# and VB.NET.

Steps to write data into an Excel file programmatically:

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

Create a new C# console application

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

Install NuGet package

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

C#

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 write data into an existing Excel file.

C#

// Create an instance of ExcelEngine
using (ExcelEngine excelEngine = new ExcelEngine())
{
  // Set the default application version as Excel 2016
  excelEngine.Excel.DefaultVersion = ExcelVersion.Excel2016;
 
  // Open existing workbook with data entered
  Assembly assembly = typeof(Program).GetTypeInfo().Assembly;
  Stream fileStream = assembly.GetManifestResourceStream("WriteData.Sample.xlsx");
  IWorkbook workbook = application.Workbooks.Open(fileStream);
 
  // Access the first worksheet from the workbook instance
  IWorksheet worksheet = workbook.Worksheets[0];
 
  // Insert sample text into cell “A1”
  worksheet.Range["A1"].Text = "Syncfusion Essential XlsIO";
 
  // Save the workbook to disk in xlsx format
  workbook.SaveAs("Output.xlsx");
}

VB.NET

'Create an instance of ExcelEngine
Using excelEngine As ExcelEngine = New ExcelEngine
 
  'Set the default application version as Excel 2016
  excelEngine.Excel.DefaultVersion = ExcelVersion.Excel2016
 
  'Open an existing workbook with data entered
  Dim assembly As Assembly = GetType(Program).GetTypeInfo.Assembly
  Dim fileStream As Stream = assembly.GetManifestResourceStream("WriteData.Sample.xlsx")
  Dim workbook As IWorkbook = application.Workbooks.Open(fileStream)
 
  'Access the first worksheet from the workbook instance
  Dim worksheet As IWorksheet = workbook.Worksheets(0)
 
  'Insert sample text into cell “A1”
  worksheet.Range("A1").Text = "Syncfusion Essential XlsIO"
 
  'Save the workbook to disk in xlsx format
  workbook.SaveAs("Output.xlsx")
 
End Using

A complete working example to write data to an existing Excel file along with input file used can be downloaded from Write Data to Existing Excel file.zip

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

Output Excel document

Take a moment to peruse the documentation, where you can find basic worksheet data manipulation options along with features like Conditional Formatting, worksheet calculations through Formulas, adding Charts in worksheet or workbook, organizing and analyzing data through Tables and Pivot Tables, appending multiple records to worksheet using Template Markers, and most importantly PDF and Image conversions with code examples.

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

An online sample link to generate Excel file.

See Also:

Read Excel from Code in C#, VB.NET

Conclusion

I hope you enjoyed learning about how to write to existing Excel in C#, VB.NET.

You can refer to our XIsIO’s feature tour page to learn about its other groundbreaking features. Explore our UG documentation and online demos to understand how to manipulate data in Excel documents.

If you are an existing user, you can access our latest components from the License and Downloads page. For new users, you can try our 30-day free trial to check out XlsIO and other Syncfusion® components.

If you have any queries or require clarification, please let us know in the comments below or contact us through our support forums, Support Tickets, or feedback portal. We are always happy to assist you!