IronXL How-Tos Load Spreadsheets How to Load Existing Spreadsheets Chaknith Bin Updated:July 28, 2025 CSV (Comma-Separated Values) file format is for tabular data where values are separated by commas, commonly used for data exchange. On the other hand, TSV (Tab-Separated Values) uses tabs to separate values, preferred when data contains commas. The DataSet class in Microsoft's .NET is a part of the ADO.NET (ActiveX Data Objects for .NET) technology. It's often used in database-related applications and allows you to work with data from various sources like databases, XML, and more. Data contained in Excel file formats such as XLSX, XLS, XLSM, XLTX, CSV, and TSV as well as a DataSet object can be loaded into an Excel spreadsheet using IronXL. How to Load Existing Spreadsheets Download the C# library to load spreadsheet Prepare the file or data object to be loaded into the spreadsheet Use the Load method to load the data into a workbook object Use the LoadWorkSheetsFromDataSet method to load data from a DataSet object Export the workbook as an Excel file Get started with IronXL Start using IronXL in your project today with a free trial. First Step: Start for Free Load Spreadsheet Example Use the static method Load to load an existing Excel workbook. The method supports XLSX, XLS, XLSM, XLTX, CSV, and TSV file formats. In cases where the workbook is protected with a password, you can pass the password as the second parameter to the method. The method also accepts workbook data in the form of a byte array or a stream, where the dedicated FromByteArray and FromStream methods can be used, respectively. :path=/static-assets/excel/content-code-examples/how-to/load-spreadsheet-load-spreadsheet.cs using IronXL; // Supported for XLSX, XLS, XLSM, XLTX, CSV and TSV WorkBook workBook = WorkBook.Load("sample.xlsx"); Imports IronXL ' Supported for XLSX, XLS, XLSM, XLTX, CSV and TSV Private workBook As WorkBook = WorkBook.Load("sample.xlsx") $vbLabelText $csharpLabel Load CSV file While the Load method can read all available file formats, it is recommended to use the LoadCSV method specifically for CSV file formats for optimal handling. :path=/static-assets/excel/content-code-examples/how-to/load-spreadsheet-load-csv.cs using IronXL; // Load CSV file WorkBook workBook = WorkBook.LoadCSV("sample.csv"); Imports IronXL ' Load CSV file Private workBook As WorkBook = WorkBook.LoadCSV("sample.csv") $vbLabelText $csharpLabel Load DataSet The DataSet class in Microsoft .NET is used for managing and working with data in a disconnected, in-memory representation. This DataSet can also be loaded into the workbook using the LoadWorkSheetsFromDataSet method. In the code example below, an empty DataSet is created; however, it's more common to instantiate the DataSet from a database query. :path=/static-assets/excel/content-code-examples/how-to/load-spreadsheet-load-dataset.cs using IronXL; using System.Data; // Create dataset DataSet dataSet = new DataSet(); // Create workbook WorkBook workBook = WorkBook.Create(); // Load DataSet WorkBook.LoadWorkSheetsFromDataSet(dataSet, workBook); Imports IronXL Imports System.Data ' Create dataset Private dataSet As New DataSet() ' Create workbook Private workBook As WorkBook = WorkBook.Create() ' Load DataSet WorkBook.LoadWorkSheetsFromDataSet(dataSet, workBook) $vbLabelText $csharpLabel Frequently Asked Questions What file formats can be loaded using this library? IronXL supports loading XLSX, XLS, XLSM, XLTX, CSV, and TSV file formats. How can I load a password-protected Excel workbook? To load a password-protected Excel workbook using IronXL, use the Load method and pass the password as the second parameter. Can this library load data directly from a byte array or stream? Yes, IronXL can load workbook data from a byte array using the LoadFromByteArray method and from a stream using the LoadFromStream method. What is the recommended method for loading CSV files? While the Load method can read CSV files, it is recommended to use the LoadCSV method for optimal handling of CSV file formats with IronXL. How does this library handle loading data from a DataSet object? IronXL can load data from a DataSet object using the LoadWorkSheetsFromDataSet method, creating one worksheet per DataTable in the DataSet. What is the purpose of the DataSet class in .NET? The DataSet class in .NET is used for managing and working with data in a disconnected, in-memory representation, typically filled from database queries. How can I get started with using this library to load spreadsheets? To get started with IronXL, download the C# library from NuGet, prepare your file or data object, and use the Load method to load the data into a workbook object. Chaknith Bin Chat with engineering team now Software Engineer Chaknith is the Sherlock Holmes of developers. It first occurred to him he might have a future in software engineering, when he was doing code challenges for fun. His focus is on IronXL and IronBarcode, but he takes pride in helping customers with every product. Chaknith leverages his knowledge from talking directly with customers, to help further improve the products themselves. His anecdotal feedback goes beyond Jira tickets and supports product development, documentation and marketing, to improve customer’s overall experience.When he isn’t in the office, he can be found learning about machine learning, coding and hiking. Ready to Get Started? Free NuGet Download Total downloads: 1,531,849 View Licenses