5 Essential .NET Libraries Every Developer Should Master

As .NET developers, we often find ourselves building applications that require PDF generation, mock data, Excel integration, performance tuning, or resilient networking. Instead of reinventing the wheel, we can rely on powerful, battle-tested libraries that make our jobs easier and our applications more robust.

In this blog post, we’ll explore five exceptional .NET libraries that help us achieve these goals:

QuestPDF
Bogus
ClosedXML
BenchmarkDotNet
Polly

Each section provides:

A description of the library
Key use cases
Pseudocode to get you started
A link to the full working code on GitHub

1. QuestPDF – Professional PDF Generation for .NET

QuestPDF is a modern .NET library for creating PDF files using a fluent, code-first approach. Unlike traditional PDF libraries that require absolute positioning and tedious layout logic, QuestPDF provides a high-level, declarative API to structure documents with ease.

Use Cases:

Generating invoices, quotations, certificates
Creating printable reports with tables and charts
Exporting dynamic content to PDF

Key Features

Headers, footers, tables, grids, text styling
Image embedding and pagination
PDF preview during development

Pseudocode Example

Create class : IDocument
  Implement Compose()
    Define page size, margins
    Add header with title, date, logo
    Add customer and invoice details
    Add table of items with totals

Call: new QuotationDocument().GeneratePdf("Quote.pdf");

Working code on GitHub and Documentation

2. Bogus – Realistic Fake Data Generator

Bogus is a powerful .NET library to generate fake but realistic data for testing and development. It supports everything from names and emails to complex object graphs.

Use Cases

Seeding test databases
Generating demo data for UI/UX
Populating mock APIs

Key Features

Localized data (e.g., Indian names, addresses)
Faker rules for nested data
Supports rules, formatters, ranges

Pseudocode Example

Create Faker<Customer> with name, email, address
Generate 10 customers
Create Faker<Invoice> and assign to each customer
Create Faker<Payment> and link to each invoice

Working code on GitHub and Documentation

3. ClosedXML – Read/Write Excel Files Easily

ClosedXML allows you to read and write Excel .xlsx files in .NET without requiring Microsoft Office. It’s built on top of OpenXML SDK with a simpler API.

Use Cases

Exporting reports or summaries to Excel
Importing structured data from Excel sheets
Replacing manual data entry with automation

Key Features

Create, read, update .xlsx files
Tables, styling, formatting, validation
Multiple worksheets
Works in Windows, Linux, macOS

Pseudocode Example

Export:
  Create XLWorkbook
  Add Worksheets: Customers, Invoices, Payments
  InsertTable() for each list
  workbook.SaveAs("Data.xlsx")

Import:
  Load workbook
  Read rows, map to model objects

Working code on GitHub and Documentation

4. BenchmarkDotNet – Performance & Memory Profiler

BenchmarkDotNet is a gold-standard benchmarking library that helps you measure execution time and memory usage of code segments precisely.

Use Cases

Comparing algorithm efficiency
Measuring memory allocations
Analyzing hot paths in performance-critical apps

Key Features

Mean, StdDev, Allocations, GC impact
RankColumn, memory diagnoser
Export to CSV, HTML, JSON

Pseudocode Example

[Benchmark] ForLoop()
[Benchmark] LinqSum()
[Benchmark] ParallelSum()

Use [GlobalSetup] for test data
Run: BenchmarkRunner.Run<YourClass>()

Working code on GitHub and Documentation

5. Polly – Resilience and Fault Tolerance for .NET

Polly is a resilience and transient-fault-handling library that allows developers to define sophisticated policies such as Retry, Circuit Breaker, Fallback, and Timeout.

Use Cases

Retrying failed network/API calls
Implementing fallback logic for service downtime
Protecting APIs with circuit breakers
Managing bulkhead isolation

Key Features

Retry, Timeout, Fallback, CircuitBreaker
Fluent, composable policies
Async and sync support
Integration with HttpClientFactory

Pseudocode Example

retry = Policy.Handle<Exception>().Retry(3)
fallback = Policy.Fallback(() => return default)
timeout = Policy.Timeout(2 sec)

wrap = fallback.Wrap(retry).Wrap(timeout)
wrap.Execute(() => RiskyMethod())

Vinir Shah