How to Create Excel XLSX Using a .NET C# Server-Side API

March 10 2025
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Quick Start Guide
Tutorial Concept	Learn how to programmatically generate an Excel XLSX document using C# in a .NET server-side ASP.NET application. In this blog, we'll cover how to utilize DsExcel in an ASP.NET server-side application to import and export Excel files, and how to programmatically generate and alter Excel files on the server side.
What You Will Need	Visual Studio 2022 .NET 6+ Document Solutions for Excel, .NET - Download a 30-Day Free Trial
Controls Referenced	Document Solutions for Excel, .NET - .NET Document API Library Documentation \| Demo Explorer

Quick Start Guide

Tutorial Concept

Learn how to programmatically generate an Excel XLSX document using C# in a .NET server-side ASP.NET application. In this blog, we'll cover how to utilize DsExcel in an ASP.NET server-side application to import and export Excel files, and how to programmatically generate and alter Excel files on the server side.

What You Will Need

Visual Studio 2022
.NET 6+
Document Solutions for Excel, .NET - Download a 30-Day Free Trial

Controls Referenced

Document Solutions for Excel, .NET - .NET Document API Library

Documentation | Demo Explorer

Document Solutions for Excel (DsExcel, previously GcExcel) is a server-side Excel API that can generate, load, save, convert, calculate, format, parse, and export spreadsheets in any .NET Standard targeted application. With full .NET 8+ support for Windows, Linux, and Mac, DsExcel can deploy to Azure (or any other cloud platform) without any Excel dependencies.

With DsExcel, you can easily create, load, and save Excel documents without having Microsoft Excel on your system. With the VSTO-style API, you can query, generate, and export any spreadsheet, create custom styles, import spreadsheets, and calculate data.

You can also add sorting, filtering, formatting, conditional formatting and data validation, grouping, sparklines, charts, shapes, pictures, slicers, comments, hyperlinks, themes, etc., using the same elements as VS Tools for Office.

Ready to Try It Out? Download Document Solutions for Excel Today!

Features and functionalities covered in this blog working with XLSX in ASP.NET:

Importing an Excel file on the server side
Exporting your server-side Excel files
Programming with DsExcel on the server side
Generating Excel spreadsheets on the server side

Let's take a look at the AspNetCoreDemo samples.

Creating an ASP.NET Core MVC Project

First, we'll create a basic ASP.NET Core MVC application. You can also use DsExcel in any ASP.NET Core application when using Web API, Angular, or React.js.

Creating ASP.NET Core MVC Project

Add References to the DsExcel NuGet Package

Right-click Dependencies and choose Manage NuGet Packages
Choose NuGet Gallery | Home from Package Source on the top right
Under the Browse tab, type DS.Documents.Excel and add the package

Add the DsExcel Namespace to the Controller Class

Note: 'Document Solutions' was previously known as 'GrapeCity Documents.' The previous product name currently remains on our NuGet packages.

In your controller class - HomeController.cs, import the following namespace:

using GrapeCity.Documents.Excel;

Importing an Excel File on the Server Side

You can upload an Excel file on the client side, load and open it on the server side, and then return it in JSON syntax.

Create the IActionResult method in the controller class you just added
Create a DsExcel workbook
Load the Excel file sent from the client side into the workbook
If you want to show this file back on the client side by displaying the file in a spreadsheet editor, you can use our client-side editor, SpreadJS. SpreadJS uses JSON syntax to display the Excel file, so you can convert the file on the server side to JSON using the workbook.ToJson() function. Finally, return this JSON (named 'sjs' in the code) to the client side.

Use the following code for the above steps:

[HttpPost]
public IActionResult ImportExcel()
{
    Workbook workbook = new Workbook();
    workbook.Open(Request.Body);
    var sjs = workbook.ToJson();
    return Ok(sjs);
}

Exporting an Excel File on the Server Side

If you have edited an Excel file in the SpreadJS editor, you can export the file to Excel using DsExcel on the server side. Extract the JSON (of the edited Excel file) on the server side using the workbook.FromJson method. Then, convert the JSON to xlsx and download it on the server side.

[HttpPost]
public FileResult ExportExcel(string fileName = "")
{
            // create a new Workbook and invoke FromJson to restore workbook from sjs
            // the sjs is from spread.sheets by invoking this.spread.toJSON()
            Workbook workbook = new Workbook();
            workbook.FromJson(HttpContext.Request.Body);
 
            MemoryStream stream = new MemoryStream();
            workbook.Save(stream);
            stream.Seek(0, SeekOrigin.Begin);
 
            byte[] bytes = new byte[stream.Length];
            stream.Read(bytes, 0, bytes.Length);
 
            var contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            var downloadFile = string.Format("attachment;filename={0}.xlsx;", string.IsNullOrEmpty(fileName) ? Guid.NewGuid().ToString() : WebUtility.UrlEncode(fileName));
 
            return File(bytes, contentType, downloadFile);
}

Programming and Generating Server-Side Excel Spreadsheets

You can program with DsExcel and generate server-side Excel spreadsheets without needing MS Excel.

In a function, create a workbook using DsExcel
Convert the workbook to JSON and return it to the client side

Note: We are only creating a BidTracker.xlsx spreadsheet in this example. This sample demonstrates additional features that can be programmed with DsExcel on the server side.

[HttpGet("{caseName}")]
      public IActionResult GetSSJsonFromUseCase(string caseName)
      {
          Workbook workbook = CreateWorkbookByCaseName(caseName);
          var sjs = workbook.ToJson();
          return Ok(sjs);
      }
 
      private Workbook CreateWorkbookByCaseName(string caseName)
      {
          switch (caseName)
          {
              case "BidTracker":
                  return GetBidTracker();
              default:
                  break;
          }
 
          return new Workbook();
      }

Create a function to generate an Excel spreadsheet. This example demonstrates how to use different DsExcel features:

Creating a workbook and worksheet
Adding data
Adding a table
Named styles and conditional formatting

private Workbook GetBidTracker()
{
            Workbook workbook = new Workbook();
            IWorksheet worksheet = workbook.Worksheets[0];

            //***********************Set RowHeight & ColumnWidth***************
            worksheet.StandardHeight = 30;
            worksheet.Range["1:1"].RowHeight = 57.75;
            worksheet.Range["2:9"].RowHeight = 30;
            worksheet.Range["A:A"].ColumnWidth = 2.71;
            worksheet.Range["B:B"].ColumnWidth = 11.71;
            worksheet.Range["C:C"].ColumnWidth = 28;
            worksheet.Range["D:D"].ColumnWidth = 22.425;
            worksheet.Range["E:E"].ColumnWidth = 16.71;
            worksheet.Range["F:F"].ColumnWidth = 28;
            worksheet.Range["G:H"].ColumnWidth = 16.71;
            worksheet.Range["I:I"].ColumnWidth = 2.71;

            //**************************Set Table Value & Formulas*********************
            ITable table = worksheet.Tables.Add(worksheet.Range["B2:H9"], true);
            worksheet.Range["B2:H9"].Value = new object[,]
            {
            { "BID #", "DESCRIPTION", "DATE RECEIVED", "AMOUNT", "PERCENT COMPLETE", "DEADLINE", "DAYS LEFT" },
            { 1, "New Emergency care facility", null, 2000, 0.5, null, null },
            { 2, "Service Contract Extension", null, 3500, 0.75, null, null },
            { 3, "Preventive Maintenance Agreement", null, 5000, 0.8, null, null },
            { 4, "Full restoration contract", null, 4000, 0.2, null, null },
            { 5, "Hampton Inn, Burlington", null, 4000, 1.00, null , null },
            { 6, "New invitation to bid", null, 1500, 0.0, null , null },
            { 7, "Children's hospital - new admin building", null, 5000, 0.65, null, null },
            };
            worksheet.Range["B1"].Value = "Bid Details";
            worksheet.Range["D3"].Formula = "=TODAY()-10";
            worksheet.Range["D4:D5"].Formula = "=TODAY()-20";
            worksheet.Range["D6"].Formula = "=TODAY()-10";
            worksheet.Range["D7"].Formula = "=TODAY()-28";
            worksheet.Range["D8"].Formula = "=TODAY()-17";
            worksheet.Range["D9"].Formula = "=TODAY()-15";
            worksheet.Range["G3:G9"].Formula = "=[@[DATE RECEIVED]]+30";
            worksheet.Range["H3:H9"].Formula = "=[@DEADLINE]-TODAY()";
            
            //****************************Set Table Style********************************
            
            //****************************Set Table Style********************************
            ITableStyle tableStyle = workbook.TableStyles.Add("Bid Tracker");
            workbook.DefaultTableStyle = "Bid Tracker";
            
            var wholeTableStyle = tableStyle.TableStyleElements[TableStyleElementType.WholeTable];
            
            //Set WholeTable element style.
            wholeTableStyle.Font.Color =  Color.FromArgb(89, 89, 89);
            wholeTableStyle.Borders.Color = Color.FromArgb(89, 89, 89);
            wholeTableStyle.Borders[BordersIndex.EdgeLeft].LineStyle = BorderLineStyle.Thin;
            wholeTableStyle.Borders[BordersIndex.EdgeRight].LineStyle = BorderLineStyle.Thin;
            wholeTableStyle.Borders[BordersIndex.EdgeTop].LineStyle = BorderLineStyle.Thin;
            wholeTableStyle.Borders[BordersIndex.EdgeBottom].LineStyle = BorderLineStyle.Thin;
            wholeTableStyle.Borders[BordersIndex.InsideVertical].LineStyle = BorderLineStyle.Thin;
            wholeTableStyle.Borders[BordersIndex.InsideHorizontal].LineStyle = BorderLineStyle.Thin;
            
            var headerRowStyle = tableStyle.TableStyleElements[TableStyleElementType.HeaderRow];
            
            //Set HeaderRow element style.
            headerRowStyle.Borders.Color = Color.FromArgb(89, 89, 89);
            headerRowStyle.Borders[BordersIndex.EdgeLeft].LineStyle = BorderLineStyle.Thin;
            headerRowStyle.Borders[BordersIndex.EdgeRight].LineStyle = BorderLineStyle.Thin;
            headerRowStyle.Borders[BordersIndex.EdgeTop].LineStyle = BorderLineStyle.Thin;
            headerRowStyle.Borders[BordersIndex.EdgeBottom].LineStyle = BorderLineStyle.Thin;
            headerRowStyle.Borders[BordersIndex.InsideVertical].LineStyle = BorderLineStyle.Thin;
            headerRowStyle.Borders[BordersIndex.InsideHorizontal].LineStyle = BorderLineStyle.Thin;
            headerRowStyle.Interior.Color = Color.FromArgb(131, 95, 1);
            headerRowStyle.Interior.PatternColor = Color.FromArgb(254, 184, 10);
            
            
            var totalRowStyle = tableStyle.TableStyleElements[TableStyleElementType.TotalRow];
            
            //Set TotalRow element style.
            totalRowStyle.Borders.Color = Color.White;
            totalRowStyle.Borders[BordersIndex.EdgeLeft].LineStyle = BorderLineStyle.Thin;
            totalRowStyle.Borders[BordersIndex.EdgeRight].LineStyle = BorderLineStyle.Thin;
            totalRowStyle.Borders[BordersIndex.EdgeTop].LineStyle = BorderLineStyle.Thin;
            totalRowStyle.Borders[BordersIndex.EdgeBottom].LineStyle = BorderLineStyle.Thin;
            totalRowStyle.Borders[BordersIndex.InsideVertical].LineStyle = BorderLineStyle.Thin;
            totalRowStyle.Borders[BordersIndex.InsideHorizontal].LineStyle = BorderLineStyle.Thin;
            totalRowStyle.Interior.Color = Color.FromArgb(131, 95, 1);
            
            
            //***********************************Set Named Styles*****************************
            IStyle titleStyle = workbook.Styles["Title"];
            titleStyle.Font.Name = "Calibri";
            titleStyle.Font.Size = 36;
            titleStyle.Font.Color = Color.FromArgb(0,0,0);
            titleStyle.IncludeAlignment = true;
            titleStyle.VerticalAlignment = VerticalAlignment.Center;
            
            IStyle heading1Style = workbook.Styles["Heading 1"];
            heading1Style.IncludeAlignment = true;
            heading1Style.HorizontalAlignment = HorizontalAlignment.Right;
            heading1Style.VerticalAlignment = VerticalAlignment.Bottom;
            heading1Style.Borders[BordersIndex.EdgeBottom].LineStyle = BorderLineStyle.None;
            heading1Style.Font.Size = 14;
            heading1Style.Font.Color = Color.Black;
            heading1Style.Font.Bold = false;
            heading1Style.IncludePatterns = true;
            heading1Style.Interior.Color = Color.FromArgb(255, 255, 255);
            
            IStyle dateStyle = workbook.Styles.Add("Date");
            dateStyle.IncludeNumber = true;
            dateStyle.NumberFormat = "m/d/yyyy";
            dateStyle.IncludeAlignment = true;
            dateStyle.HorizontalAlignment = HorizontalAlignment.Right;
            dateStyle.VerticalAlignment = VerticalAlignment.Center;
            dateStyle.IncludeFont = false;
            dateStyle.IncludeBorder = false;
            dateStyle.IncludePatterns = false;
            
            IStyle commaStyle = workbook.Styles["Comma"];
            commaStyle.IncludeNumber = true;
            commaStyle.NumberFormat = "#,##0_);(#,##0)";
            commaStyle.IncludeAlignment = true;
            commaStyle.HorizontalAlignment = HorizontalAlignment.Right;
            commaStyle.VerticalAlignment = VerticalAlignment.Center;
            
            IStyle normalStyle = workbook.Styles["Normal"];
            normalStyle.HorizontalAlignment = HorizontalAlignment.Right;
            normalStyle.VerticalAlignment = VerticalAlignment.Center;
            normalStyle.WrapText = true;
            normalStyle.Font.Color = Color.FromArgb(89, 89, 89);
            
            IStyle currencyStyle = workbook.Styles["Currency"];
            currencyStyle.NumberFormat = "$#,##0.00";
            currencyStyle.IncludeAlignment = true;
            currencyStyle.HorizontalAlignment = HorizontalAlignment.Right;
            currencyStyle.VerticalAlignment = VerticalAlignment.Center;
            
            IStyle percentStyle = workbook.Styles["Percent"];
            percentStyle.IncludeAlignment = true;
            percentStyle.HorizontalAlignment = HorizontalAlignment.Right;
            percentStyle.VerticalAlignment = VerticalAlignment.Center;
            percentStyle.IncludeFont = true;
            percentStyle.Font.Name = "Calibri";
            percentStyle.Font.Size = 14;
            percentStyle.Font.Bold = true;
            percentStyle.Font.Color = Color.FromArgb(89, 89, 89);
            
            IStyle comma0Style = workbook.Styles["Comma [0]"];
            comma0Style.NumberFormat = "#,##0_);(#,##0)";
            comma0Style.IncludeAlignment = true;
            
            comma0Style.VerticalAlignment = VerticalAlignment.Center;
            
            //************************************Add Conditional Formatting****************
            IDataBar dataBar = worksheet.Range["F3:F9"].FormatConditions.AddDatabar();
            dataBar.MinPoint.Type = ConditionValueTypes.Number;
            dataBar.MinPoint.Value = 1;
            dataBar.MaxPoint.Type = ConditionValueTypes.Number;
            dataBar.MaxPoint.Value = 0;
            
            dataBar.BarFillType = DataBarFillType.Gradient;
            dataBar.BarColor.Color = Color.FromArgb(126, 194, 211);
            dataBar.Direction = DataBarDirection.Context;
            
            dataBar.AxisColor.Color = Color.Black;
            dataBar.AxisPosition = DataBarAxisPosition.Automatic;
            
            dataBar.NegativeBarFormat.ColorType = DataBarNegativeColorType.Color;
            dataBar.NegativeBarFormat.Color.Color = Color.Red;
            dataBar.ShowValue = true;
            
            //****************************************Use NamedStyle**************************
            worksheet.SheetView.DisplayGridlines = false;
            table.TableStyle = tableStyle;
            worksheet.Range["B1"].Style = titleStyle;
            worksheet.Range["B1"].WrapText = false;
            worksheet.Range["B2:H2"].Style = heading1Style;
            worksheet.Range["B3:B9"].Style = commaStyle;
            worksheet.Range["C3:C9"].Style = normalStyle;
            worksheet.Range["D3:D9"].Style = dateStyle;
            worksheet.Range["E3:E9"].Style = currencyStyle;
            worksheet.Range["F3:F9"].Style = percentStyle;
            worksheet.Range["G3:G9"].Style = dateStyle;
            worksheet.Range["H3:H9"].Style = comma0Style;
             
            return workbook;
}

This is what the Excel file should look like:

Server Side XLSX File

Check out this sample to understand the complete MVC workflow (how to display the Excel file back on the client and import the client-side edited Excel file).

Conclusion

In this article, we explored how to leverage Document Solutions for Excel (DsExcel) to create, manage, and export Excel files on the server side using C# and ASP.NET Core. We covered everything from importing and exporting Excel files in various formats to using powerful features like formatting, data validation, formulas, and conditional formatting—all without installing Microsoft Excel on your system.

DsExcel provides a robust API for working with Excel files in .NET applications, enabling developers to handle Excel file generation, manipulation, and conversion seamlessly in server-side environments. With its extensive support for styling, table creation, and even chart generation, DsExcel simplifies the process of automating Excel document workflows within web applications.

By utilizing the AspNetCoreDemo sample, we demonstrated how to integrate these features into an ASP.NET Core MVC project, making it easier than ever to work with Excel files in your server-side applications. From creating customized workbooks to integrating dynamic data, DsExcel empowers developers to build sophisticated, Excel-driven applications without relying on Excel itself.

There are many more features that can be programmed with DsExcel on the server side. For a complete list, check out Document Solutions for Excel. If you're ready to take your server-side Excel processing to the next level, download DsExcel today by clicking the link below and exploring all the features it has to offer. Happy coding!

Ready to Try It Out? Download Document Solutions for Excel, .NET Edition, Today!