Excel remains one of the most widely used tools for managing and analyzing data due to its powerful features and user-friendly interface. In C# applications, developers often need to generate reports, export database results, or automate tasks by writing directly to Excel files.

To achieve this efficiently, developers often turn to third-party libraries. Spire.XLS for .NET makes it simple to write to Excel programmatically without relying on Microsoft Excel. With Spire.XLS, you can insert text, numbers, dates, formulas, or even bulk datasets such as arrays, DataTables, and lists into Excel worksheets. This provides a fast, flexible, and reliable way to automate Excel writing in C# applications.

On this page:

• Getting Started with Spire.XLS for .NET
• How to Create a New Excel File in C#
• Write Different Data Types to Excel Cells
• Write Bulk Data to Excel Sheets
• Save and Export Excel Files
• Common Issues and Solutions
• Conclusion
• FAQs

Getting Started with Spire.XLS for .NET

What’s Spire.XLS for .NET

Spire.XLS for .NET is a professional .NET Excel library developed by E-iceblue. It allows developers to write to Excel files in C# and perform a wide range of operations including creating, editing, reading, and exporting Excel documents—without requiring Microsoft Excel to be installed.

Key features include:

• Write and update Excel files programmatically.
• Support for Excel formats (XLS, XLSX, CSV, ODS).
• Advanced features such as formulas, charts, pivot tables, and data validation.
• Export Excel to PDF, HTML, and image formats.
• High performance with large datasets, suitable for desktop, server, and web applications.

How to Install Spire.XLS for .NET

Option 1: Install via NuGet (recommended)

• Open Visual Studio.
• Navigate to Tools > NuGet Package Manager > Manage NuGet Packages for Solution.
• Search for Spire.XLS and install it.

Or, install it directly using the Package Manager Console :

PM> Install-Package Spire.XLS

Option 2: Manual installation

• Download the Spire.XLS package from our official website
• Add a reference to Spire.Xls.dll in your project.

Once installed, you’re ready to start writing to Excel in C#.

How to Create a New Excel File in C#

The first step is to create a new workbook and add a worksheet. Here’s how:

using Spire.Xls;

namespace CreateNewExcel
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create a new workbook
            Workbook workbook = new Workbook();

            // Remove default worksheets
            workbook.Worksheets.Clear();

            // Add a worksheet
            Worksheet sheet = workbook.Worksheets.Add("Report");

            // Save the empty Excel file
            workbook.SaveToFile("NewExcelFile.xlsx", ExcelVersion.Version2016);
            workbook.Dispose();
        }
    }
}

At this point, you have created an empty Excel file with a worksheet named “Report”. Next, let’s write data into it.

Write Different Data Types to Excel Cells in C#

Spire.XLS allows you to write various data types directly to Excel cells. Below are common examples:

Write Text Values

sheet.Range["A1"].Text = "Hello Excel!";

Write Numeric Values

sheet.Range["A2"].NumberValue = 123.45;

Write Date and Time

sheet.Range["A3"].DateTimeValue = DateTime.Now;
sheet.Range["A3"].NumberFormat = "yyyy-mm-dd hh:mm";

Write Boolean Values

sheet.Range["A4"].BooleanValue = true;

Write TimeSpan Values

sheet.Range["A5"].TimeSpanValue = new TimeSpan(2, 30, 0); // 2 hours 30 minutes;
sheet.Range["A5"].NumberFormat = "[h]:mm:ss";

Insert Formulas

sheet.Range["A6"].Formula = "=SUM(A2,100)";

Insert HTML Formatted Strings

string htmlText = "<span style=\"font-family: Times New Roman; color: blue; font-size: 15pt;\">Hello
<strong>Spire.XLS</strong></span>";
sheet.Range["A7"].HtmlString = htmlText;

Write General Values Without Specific Type

sheet.Range["A8"].Value = "General Value";

Output:

You might also be interested in: How to Read Excel Files in C#

Write Bulk Data to Excel Sheets in C#

When dealing with larger datasets, writing values cell by cell isn’t efficient. Spire.XLS provides methods to insert arrays , and DataTables directly. Other data structures can be converted to arrays or DataTables before being written to the Excel sheet.

Write Arrays to Excel

Spire.XLS provides the Worksheet.InsertArray(string[] stringArray, int firstRow, int firstColumn, bool isVertical) method, allowing developers to insert one-dimensional or two-dimensional arrays into a specified range of cells in a worksheet.

string[,] data = {
    { "Name", "Age", "Country" },
    { "Alice", "30", "USA" },
    { "Bob", "28", "UK" },
    { "Charlie", "35", "Canada" }
};
sheet.InsertArray(data, 1, 1);

Output:

Write DataTables to Excel

To import data from a DataTable to a worksheet, use the Worksheet.InsertDataTable(DataTable dataTable, bool columnHeaders, int firstRow, int firstColumn, bool transTypes) method.

using System.Data;

DataTable dt = new DataTable();
dt.Columns.Add("ID", typeof(int));
dt.Columns.Add("Product", typeof(string));
dt.Columns.Add("Price", typeof(double));

// Add rows
dt.Rows.Add(1, "Laptop", 1200.5);
dt.Rows.Add(2, "Tablet", 450.99);
dt.Rows.Add(3, "Phone", 799.0);

// Insert DataTable starting at cell A1
sheet.InsertDataTable(dt, true, 1, 1, true);

Output:

On the contrary, you can export data from Excel to DataTable by using the ExportDataTable method of the Worksheet class.

Write Lists to Excel

While Spire.XLS does not provide a direct method for writing lists to Excel, you can convert lists to a DataTable and then use the InsertDataTable method to write the DataTable to Excel.

using Spire.Xls;
using System.Data;

namespace WriteListToExcel
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create a Workbook instance
            Workbook workbook = new Workbook();

            // Remove default worksheets
            workbook.Worksheets.Clear();

            // Add a worksheet and name it
            Worksheet worksheet = workbook.Worksheets.Add("Students");

            // Create a list with student data
            List<Student> students = new List<Student>
            {
                new Student("Michael", "Johnson", 20, "Computer Science", 3.8),
                new Student("Sarah", "Williams", 22, "Mathematics", 3.6),
                new Student("Jessica", "Brown", 19, "Physics", 3.9),
                new Student("David", "Smith", 21, "Chemistry", 3.7),
                new Student("Emily", "Davis", 23, "Biology", 3.5)
            };

            // Convert the list to DataTable
            DataTable dataTable = ConvertListToDataTable(students);

            // Write DataTable to the worksheet
            worksheet.InsertDataTable(dataTable, true, 1, 1, true);

            // Set column width
            worksheet.AllocatedRange.ColumnWidth = 12;

            // Align content to left
            worksheet.AllocatedRange.HorizontalAlignment = HorizontalAlignType.Left;

            // Save to an Excel file
            workbook.SaveToFile("InsertStudents.xlsx", ExcelVersion.Version2016);

            // Dispose resources
            workbook.Dispose();
        }

        static DataTable ConvertListToDataTable(List<Student> students)
        {
            DataTable dataTable = new DataTable();

            // Add columns
            dataTable.Columns.Add("FirstName", typeof(string));
            dataTable.Columns.Add("LastName", typeof(string));
            dataTable.Columns.Add("Age", typeof(int));
            dataTable.Columns.Add("Major", typeof(string));
            dataTable.Columns.Add("GPA", typeof(double));

            // Add rows
            foreach (var student in students)
            {
                DataRow row = dataTable.NewRow();
                row["FirstName"] = student.FirstName;
                row["LastName"] = student.LastName;
                row["Age"] = student.Age;
                row["Major"] = student.Major;
                row["GPA"] = student.GPA;
                dataTable.Rows.Add(row);
            }

            return dataTable;
        }
    }

    class Student
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int Age { get; set; }
        public string Major { get; set; }
        public double GPA { get; set; }

        public Student(string firstName, string lastName, int age, string major, double gpa)
        {
            FirstName = firstName;
            LastName = lastName;
            Age = age;
            Major = major;
            GPA = gpa;
        }
    }
}

Output:

Save and Export Excel Files

After writing data, you’ll want to save or export the Excel file. Spire.XLS supports multiple formats including XLSX, CSV, and PDF .

// Save as XLSX
workbook.SaveToFile("Output.xlsx", ExcelVersion.Version2016);

// Save as CSV
workbook.SaveToFile("Output.csv", ",", Encoding.UTF8);

// Export as PDF
workbook.SaveToFile("Output.pdf", FileFormat.PDF);

For web applications, you can also save to a MemoryStream :

using (MemoryStream ms = new MemoryStream())
{
    workbook.SaveToStream(ms, FileFormat.Version2016);
    // Write to Response in ASP.NET if needed
}

Common Issues and Solutions

1. Incorrect Date or Time Format

Issue: Dates/times appear as serial numbers.

Solution :

• Apply a proper number format to the cell:

sheet.Range["A1"].DateTimeValue = DateTime.Now;
sheet.Range["A1"].NumberFormat = "yyyy-mm-dd hh:mm";

2. Data Overwriting or Misaligned

Issue : Writing arrays or DataTables overwrites existing data unintentionally.

Solution :

• Check firstRow and firstColumn parameters in InsertArray() or InsertDataTable().
• Use separate worksheets or offset ranges if necessary.

3. Large Dataset Performance Issues

Issue : Writing thousands of rows is slow.

Solution :

• Use bulk writing methods instead of looping cell by cell.
• Apply styles after inserting data to avoid repeated formatting overhead.

4. Formula Not Calculating Correctly

Issue : Excel formulas inserted via sheet.Range["A1"].Formula do not return expected results.

Solution :

• Ensure the formula syntax is correct for Excel (e.g., =SUM(A2:A10)).
• Call workbook.CalculateAllValue() to update all formulas before saving if needed.

Conclusion

Writing to Excel in C# doesn’t have to be complex. With Spire.XLS for .NET , you can seamlessly write different data types—whether individual values or large datasets—into Excel worksheets. The library also provides support for styling, formulas, and advanced formatting, ensuring your Excel files are not only accurate but also presentation-ready.

By using efficient bulk-writing techniques like arrays and DataTables, you can handle both small and large data operations with ease. If your goal is to write to Excel files quickly and reliably , Spire.XLS gives you the tools you need—without the overhead of Microsoft Excel.

FAQs

Q1. Can I write to an existing Excel file with Spire.XLS?

Yes. Use workbook.LoadFromFile("file.xlsx") to open an existing file, then modify and save it.

Q2. Does Spire.XLS require Microsoft Excel to be installed?

No. It’s a standalone library that works without Excel.

Q3. Can Spire.XLS handle large Excel files with thousands of rows?

Yes. It’s optimized for high performance with large datasets.

Q4. How do I format cells while writing data?

You can style cells using properties like font, color, borders, and alignment:

sheet.Range["A1"].Style.Font.IsBold = true;
sheet.Range["A1"].Style.Color = Color.Yellow;
sheet.Range["A1"].Style.HorizontalAlignment  = HorizontalAlignType.Left;

Get a Free License

To fully experience the capabilities of Spire.XLS for .NET without any evaluation limitations, you can request a free 30-day trial license.

Creating PDFs in ASP.NET applications is a common requirement, whether you're generating invoices, reports, forms, or exporting dynamic content. To streamline this process, you can utilize Spire.PDF for .NET, a professional and lightweight library that enables developers to easily create and manipulate PDF documents programmatically, without the need for complex APIs or third-party printer drivers.

In this tutorial, we’ll show you how to create PDF documents in an ASP.NET Core Web application using Spire.PDF for .NET, with examples of creating a PDF from scratch and converting HTML to PDF.

On this page:

• Why Use Spire.PDF for .NET?
• Step-by-Step: Generate PDF in ASP.NET Core Web App
• Create PDF from HTML in ASP.NET Core
• Best Practices for ASP.NET PDF Generation
• Conclusion
• FAQs

Why Use Spire.PDF for .NET?

Step-by-Step: Generate PDF in ASP.NET Core Web App

Step 1. Create a New ASP.NET Core Web App

• Open Visual Studio .
• Select Create a new project .
• Choose ASP.NET Core Web App (Model-View-Controller) → Click Next .
• Enter a project name, e.g., PdfDemoApp.
• Select your target framework (e.g., . NET 6 , 7 , or 8 ).
• Click Create .

Step 2. Install Spire.PDF via NuGet

• Right-click on your project → Manage NuGet Packages .
• Search for Spire.PDF .
• Install the package Spire.PDF (latest stable version).

Or install using the Package Manager Console :

Install-Package Spire.PDF

Step 3. Add a Controller for PDF Generation

• Right-click on the Controllers folder → Add → Controller → MVC Controller – Empty .
• Name it: PdfController.cs.
• Replace the default code with this:

using Microsoft.AspNetCore.Mvc;
using Spire.Pdf;
using Spire.Pdf.Graphics;
using System.Drawing;

namespace PdfDemoApp.Controllers
{
    public class PdfController : Controller
    {
        public IActionResult CreatePdf()
        {
            // Create a new PDF document
            PdfDocument doc = new PdfDocument();
            PdfPageBase page = doc.Pages.Add(PdfPageSize.A4, new PdfMargins(40));

            // Draw text on the page
            PdfFont font = new PdfFont(PdfFontFamily.Helvetica, 25f);
            PdfSolidBrush brush = new PdfSolidBrush(Color.Black);
            page.Canvas.DrawString("Hello from ASP.NET Core!", font, brush, 10, 50);

            // Save to memory stream
            using (MemoryStream ms = new MemoryStream())
            {
                doc.SaveToStream(ms);
                doc.Close();
                ms.Position = 0;

                // Return PDF file
                return File(ms.ToArray(), "application/pdf", "Generated.pdf");
            }
        }
    }
}

Step 4: (Optional) Add a Button or Link in Your View

Open Views/Home/Index.cshtml (or whichever view is your homepage).

Add a button or link like this:

<div>
    <a asp-controller="Pdf" asp-action="CreatePdf" class="btn btn-primary">
        Create PDF from Scratch
    </a>
</div>

This uses ASP.NET Core tag helpers to generate the correct route (/Pdf/CreatePdf).

Step 5. Run and Test

• Press F5 to run your app.
• On the home page, click the "Create PDF from Scratch" button. This will call the CreatePdf method in PdfController and trigger a download of the generated PDF.
• If you didn’t add the button, you can still run the CreatePdf method directly by visiting this URL in your browser:

https://localhost:xxxx/Pdf/CreatePdf

(where xxxx is your local port number).

Output:

In addition to text, Spire.PDF supports adding a wide range of elements to PDF, such as images, shapes, tables, lists, hyperlinks, annotations, and watermarks. For more details and advanced usage, check the .NET PDF Tutorials.

Create PDF from HTML in ASP.NET Core

Spire.PDF allows you to convert HTML content directly into PDF files. This feature is particularly useful for generating invoices, reports, receipts, or exporting styled web pages with consistent formatting.

To render HTML as PDF, Spire.PDF relies on an external rendering engine. You can choose between Qt WebEngine or Google Chrome . In this guide, we’ll use Qt WebEngine .

Setup the Qt plugin:

1. Download the Qt WebEngine plugin for your operating system:

   • Windows x86
   • Windows x64
   • Linux x64
   • Mac x64

2. Extract the package to obtain the plugins directory, e.g.: C:\plugins-windows-x64\plugins

3. Register the plugin path inyour code:

HtmlConverter.PluginPath = @"C:\plugins-windows-x64\plugins";

Once the plugin is ready, you can follow the steps from the previous section and add the code snippet below to your controller to generate PDF output from HTML content.

using Microsoft.AspNetCore.Mvc;
using Spire.Additions.Qt;
using Spire.Pdf.Graphics;
using System.Drawing;

namespace PdfDemoApp.Controllers
{
    public class PdfController : Controller
    {
        [HttpGet]
        public IActionResult HtmlToPdf()
        {
            // Example HTML string
            string html = @"
                <html>
                  <head>
                    <style>
                      body { font-family: Arial, sans-serif; }
                      h1 { color: #2563eb; }
                    </style>
                  </head>
                  <body>
                    <h1>ASP.NET Core: Create PDF from HTML</h1>
                    <p>This PDF was generated using the Qt-based converter.</p>
                  </body>
                </html>";

            // Path to the Qt plugin folder
            // ⚠️ Ensure this folder exists on your server/deployment environment
            string pluginPath = @"C:\plugins-windows-x64\plugins";
            HtmlConverter.PluginPath = pluginPath;

            // Create a temp file path (on server side)
            string tempFile = Path.GetTempFileName();

            // Convert HTML string → PDF using Qt
            HtmlConverter.Convert(
                html,
                tempFile,
                enableJavaScript: true,
                timeout: 100000,                        // milliseconds
                pageSize: new SizeF(595, 842),          // A4 page size in points
                margins: new PdfMargins(40),            // 40pt margins
                LoadHtmlType.SourceCode                 // Load from HTML string
            );

            // Read the generated PDF into memory
            byte[] fileBytes = System.IO.File.ReadAllBytes(tempFile);

            // Clean up temp file
            System.IO.File.Delete(tempFile);

            // Return PDF to browser as download
            return File(fileBytes, "application/pdf", "HtmlToPdf.pdf");
        }
    }
}

Output:

This example converts inline HTML into a properly formatted PDF. You can also load external HTML files or URLs - see our detailed guide on Convert HTML to PDF in C# for more information.

Best Practices for ASP.NET PDF Generation

• Use memory streams instead of disk storage for performance and scalability.
• Cache static PDFs (like terms & conditions or forms) to reduce server load.
• Use HTML-to-PDF for dynamic reports with CSS styling.
• Consider templates (like Word-to-PDF with Spire.Doc) when documents have complex layouts.
• Secure sensitive PDFs with password protection or access permissions.

Conclusion

With Spire.PDF for .NET, you can easily generate PDF in ASP.NET Core applications. Whether you’re creating PDFs from scratch or performing HTML-to-PDF conversion in C# , Spire.PDF provides a reliable, developer-friendly solution—no external dependencies required.

If you also need to generate PDFs from Word documents, that feature is available via Spire.Doc for .NET, another product in the Spire family. Together, they cover the full range of PDF document generation scenarios.

By integrating these tools, developers can streamline workflows, reduce reliance on Adobe or other third-party components, and ensure consistent, professional-quality output. This makes your ASP.NET PDF solutions more scalable, maintainable, and ready for enterprise use.

FAQs

Q1. Do I need Adobe Acrobat installed on the server?

No. Spire.PDF is a standalone library and works independently of Adobe Acrobat.

Q2. Can I generate PDFs from both raw content and HTML?

Yes. You can build documents programmatically (drawing text, shapes, tables) or convert HTML pages to PDF.

Q3. Can I convert Word documents to PDF with Spire.PDF?

No. Word-to-PDF is supported by Spire.Doc for .NET, not Spire.PDF. You can use them together if your project requires it.

Q4. How can I protect generated PDFs?

Spire.PDF supports setting passwords, permissions, and digital signatures for document security.

Q5. Does Spire.PDF support ASP.NET Framework?

Yes. It works with both ASP.NET Core and ASP.NET Framework.

Get a Free License

To fully experience the capabilities of Spire.PDF for .NET without any evaluation limitations, you can request a free 30-day trial license.

HTML (HyperText Markup Language) is a markup language used to create web pages, allowing developers to build rich and visually appealing layouts. However, HTML files often contain a large number of tags, which makes them difficult to read if you only need the main content. By using Python to convert HTML to text, this problem can be easily solved. Unlike raw HTML, the converted text file strips away all unnecessary markup, leaving only clean and readable content that is easier to store, analyze, or process further.

• Install HTML to Text Converter in Python
• Python Convert HTML File to Text
• Python Convert HTML String to Text
• The Conclusion
• FAQs

Install HTML to Text Converter in Python

To simplify the task, we recommend using Spire.Doc for Python. This Python Word library allows you to quickly remove HTML markup and extract clean plain text with ease. It not only works as an HTML-to-text converter, but also offers a wide range of features—covering almost everything you can do in Microsoft Word.

To install it, you can run the following pip command:

pip install spire.doc

Alternatively, you can download the Spire.Doc package and install it manually.

Python Convert HTML Files to Text in 3 Steps

After preparing the necessary tools, let's dive into today's main topic: how to convert HTML to plain text using Python. With the help of Spire.Doc, this task can be accomplished in just three simple steps: create a new document object, load the HTML file, and save it as a text file. It’s straightforward and efficient, even for beginners. Let’s take a closer look at how this process can be implemented in code!

Code Example – Converting an HTML File to a Text File:

from spire.doc import *
from spire.doc.common import *

# Open an html file
document = Document()
document.LoadFromFile("/input/htmlsample.html", FileFormat.Html, XHTMLValidationType.none)
# Save it as a Text document.
document.SaveToFile("/output/HtmlFileTotext.txt", FileFormat.Txt)

document.Close()

The following is a preview comparison between the source document (.html) and the output document (.txt):

Note that if the HTML file contains tables, the output text file will only retain the values within the tables and cannot preserve the original table formatting. If you want to keep certain styles while removing markup, it is recommended to convert HTML to a Word document . This way, you can retain headings, tables, and other formatting, making the content easier to edit and use.

How to Convert an HTML String to Text in Python

Sometimes, we don’t need the entire content of a web page and only want to extract specific parts. In such cases, you can convert an HTML string directly to text. This approach allows you to precisely control the information you need without further editing. Using Python to convert an HTML string to a text file is also straightforward. Here’s a detailed step-by-step guide:

Steps to convert an HTML string to a text document using Spire.Doc:

• Input the HTML string directly or read it from a local file.
• Create a Document object and add sections and paragraphs.
• Use Paragraph.AppendHTML() method to insert the HTML string into a paragraph.
• Save the document as a .txt file using Document.SaveToFile() method.

The following code demonstrates how to convert an HTML string to a text file using Python:

from spire.doc import *
from spire.doc.common import *

#Get html string.
#with open(inputFile) as fp:
    #HTML = fp.read()

# Load HTML from string
html = """<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>HTML to Text Example</title>
  <style>
    body { font-family: Arial, sans-serif; margin: 20px; }
    header { background: #f4f4f4; padding: 10px; }
    nav a { margin: 0 10px; text-decoration: none; color: #333; }
    main { margin-top: 20px; }
  </style>
</head>
<body>
  <header>
    <h1>My Demo Page</h1>
    <nav>
      <a href="#">Home</a>
      <a href="#">About</a>
      <a href="#">Contact</a>
    </nav>
  </header>
  
  <main>
    <h2>Convert HTML to Text</h2>
    <p>This is a simple demo showing how HTML content can be displayed before converting it to plain text.</p>
  </main>
</body>
</html>
"""

# Create a new document
document = Document()
section = document.AddSection()
section.AddParagraph().AppendHTML(html)

# Save directly as TXT
document.SaveToFile("/output/HtmlStringTotext.txt", FileFormat.Txt)
document.Close()

Here's the preview of the converted .txt file:

The Conclusion

In today’s tutorial, we focused on how to use Python to convert HTML to a text file. With the help of Spire.Doc, you can handle both HTML files and HTML strings in just a few lines of code, easily generating clean plain text files. If you’re interested in the other powerful features of the Python Word library, you can request a 30-day free trial license and explore its full capabilities for yourself.

FAQs about Converting HTML to Text in Python

Q1: How can I convert HTML to plain text using Python?

A: Use Spire.Doc to load an HTML file or string, insert it into a Document object with AppendHTML(), and save it as a .txt file.

Q2: Can I keep some formatting when converting HTML to text?

A: To retain styles like headings or tables, convert HTML to a Word document first, then export to text if needed.

Q3: Is it possible to convert only part of an HTML page to text?

A: Yes, extract the specific HTML segment as a string and convert it to text using Python for precise control.