Complete C# Version History and Release Dates

C# version numbers follow a specific sequence without a “3.5” release, as the correct progression goes from C# 3.0 directly to C# 4.0. The confusion often arises from the .NET Framework 3.5, which contains C# 3.0 but was released separately from the language specification. Here’s the complete C# version timeline with proper release dates to help you find accurate information about the language’s evolution.

Contents

• C# Version History and Release Timeline
• Why C# 3.5 Doesn’t Exist
• .NET Framework vs C# Language Versions
• C# 5.0 Through Modern Releases
• How to Find Accurate C# Documentation

C# Version History and Release Timeline

C# has evolved through several major versions since its initial release, each introducing significant features and improvements. Here’s the complete chronological list of official C# language versions:

Early C# Versions (2000-2005)

• C# 1.0 - January 2002

  • Released alongside .NET Framework 1.0
  • Basic object-oriented features and syntax
  • Foundation for modern C# development

• C# 1.2 - April 2003

  • Released with .NET Framework 1.1
  • Minor improvements and bug fixes
  • Enhanced debugging capabilities

Major Evolution (2005-2010)

• C# 2.0 - November 2005

  • Released with .NET Framework 2.0
  • Generics support
  • Anonymous methods
  • Nullable value types
  • Iterators (yield keyword)

• C# 3.0 - November 2007

  • Released with .NET Framework 3.5
  • LINQ (Language Integrated Query)
  • Lambda expressions
  • Extension methods
  • Anonymous types
  • Implicitly typed local variables (var)

• C# 4.0 - April 2010

  • Released with .NET Framework 4.0
  • Dynamic programming
  • Named and optional parameters
  • Generic covariant and contravariant
  • COM interoperability improvements

Modern C# Era (2012-Present)

• C# 5.0 - August 2012

  • Released with .NET Framework 4.5
  • Async/await pattern
  • Caller information attributes

• C# 6.0 - July 2015

  • Released with .NET Framework 4.6
  • String interpolation
  • Null-conditional operator (?.)
  • Auto-property initializers
  • Expression-bodied members

• C# 7.0 - March 2017

  • Released with .NET Core 2.0
  • Pattern matching
  • Tuples
  • Out variables
  • Local functions
  • Binary literals

• C# 7.1 - August 2017

  • Async Main method
  • Default literal expressions
  • Inferred tuple element names

• C# 7.2 - November 2017

  • Reference semantics with value types
  • Non-trailing named arguments
  • Leading digit separator

• C# 7.3 - May 2018

  • Stackalloc arrays in nested contexts
  • Fixed statement enhancements
  • Generic constraints improvements

• C# 8.0 - September 2019

  • Nullable reference types
  • Async streams
  • Using declarations
  • Null-coalescing assignment
  • Switch expressions
  • Default interface methods

• C# 9.0 - November 2020

  • Records
  • Init-only accessors
  • Pattern matching enhancements
  • Top-level programs
  • Target-typed new expressions

• C# 10.0 - November 2021

  • Record structs
  • Extended property patterns
  • File-scoped namespaces
  • Required members
  • Global using directives

• C# 11.0 - November 2022

  • Generic math
  • Raw string literals
  • Required members on interfaces
  • List patterns
  • UTF-8 string literals

• C# 12.0 - November 2023

  • Primary constructors
  • Collection expressions
  • Alias any type
  • Experimental attributes
  • Ref and scoped parameters

Why C# 3.5 Doesn’t Exist

The confusion about “C# 3.5” stems from a misunderstanding between the .NET Framework versioning and the C# language versioning. Here’s why you won’t find any information about C# 3.5:

The Framework vs Language Distinction

The .NET Framework 3.5 was released in November 2007 and contained the C# 3.0 compiler and language features. Microsoft used this naming convention where the framework version number didn’t correspond directly to the C# language version inside it.

Key Point: .NET Framework 3.5 included C# 3.0, not C# 3.5. The framework version was simply a packaging version, while the language version was separate.

Version Numbering Logic

C# language versions follow a sequential numbering system that corresponds to major language specification releases, while .NET Framework versions used a different numbering scheme that included incremental releases and service packs.

• C# 3.0 was the language specification
• .NET Framework 3.5 was the runtime environment that delivered C# 3.0

This explains why developers searching for “C# 3.5” documentation find nothing - because there was never a C# language version 3.5, only a .NET Framework version 3.5 that contained C# 3.0.

.NET Framework vs C# Language Versions

Understanding the relationship between these versioning systems is crucial for finding accurate information:

Framework Versioning

The .NET Framework versioning was designed to package multiple technologies:

• Version 3.0: Added Windows Presentation Foundation (WPF), Windows Communication Foundation (WCF), and Windows Workflow Foundation (WF)
• Version 3.5: Added LINQ, ADO.NET Entity Framework, and other features while still containing C# 3.0

Language Versioning

C# language versions are tied to the language specification and compiler, not the framework:

• Each major C# version introduces new language features and syntax
• Language versions can be used with different framework versions
• Starting with .NET Core, language and framework versioning became more aligned

Modern Versioning (Post-.NET Core)

Since the introduction of .NET Core in 2016, the versioning has become more straightforward:

• .NET Core 2.0: C# 7.0
• .NET Core 3.0: C# 8.0
• .NET 5: C# 9.0 (skipped version 4 to avoid confusion with .NET Framework 4.x)
• .NET 6: C# 10.0
• .NET 7: C# 11.0
• .NET 8: C# 12.0
• .NET 9: C# 13.0 (preview)

C# 5.0 Through Modern Releases

For those looking for information about more recent C# versions, here’s what each major release introduced:

C# 5.0 (2012) - The Async Revolution

C# 5.0 brought revolutionary async programming capabilities:

// Before C# 5.0
Task<string> GetDataAsync()
{
    var task = new Task<string>(() => {
        Thread.Sleep(1000);
        return "Data";
    });
    task.Start();
    return task;
}

// C# 5.0 and later
async Task<string> GetDataAsync()
{
    await Task.Delay(1000);
    return "Data";
}

C# 6.0 (2015) - Productivity Focus

C# 6.0 focused on developer productivity and code simplification:

// String interpolation instead of string.Format
var name = "World";
var greeting = $"Hello, {name}!";

// Null-conditional operator
var length = name?.Length ?? 0;

// Auto-property initializers
public class Person { public string Name { get; set; } = "Unknown"; }

C# 7.0+ (2017-Present) - Modern C#

Each subsequent version has brought significant new features:

• C# 7.0: Pattern matching, tuples, local functions
• C# 8.0: Nullable reference types, async streams, switch expressions
• C# 9.0: Records, init-only accessors, top-level programs
• C# 10.0: Record structs, file-scoped namespaces
• C# 11.0: Generic math, raw string literals
• C# 12.0: Primary constructors, collection expressions

How to Find Accurate C# Documentation

When searching for C# information, follow these guidelines to find the right documentation:

Use Correct Version Numbers

Always search for the specific C# language version, not .NET Framework versions:

• ✅ Correct: “C# 8.0 features”
• ❌ Incorrect: “C# 3.5 features”
• ✅ Correct: “C# 12.0 pattern matching”
• ❌ Incorrect: “C# 3.5 LINQ” (LINQ was in C# 3.0)

Official Documentation Sources

Consult authoritative sources for accurate information:

1. Microsoft Learn - Official Microsoft documentation
2. C# Language Specification - The definitive source for language features
3. What’s New in C# - Microsoft’s guides for each version
4. GitHub .NET Repository - Source code and implementation details

Version-Specific Search Terms

When researching, include both the version number and feature name:

• “C# 8.0 nullable reference types”
• “C# 9.0 records example”
• “C# 10.0 file-scoped namespaces”

This approach will help you find accurate, version-specific information rather than getting confused by framework vs. language versioning.

Sources

1. Microsoft Learn - C# Version History
2. .NET Documentation - C# Language Versioning
3. C# Language Specification Overview
4. .NET Framework Version History
5. C# Feature Timeline by JetBrains

Conclusion

Understanding the correct C# version numbering is essential for finding accurate documentation and avoiding confusion. The key takeaways are:

1. No C# 3.5 exists - The correct version was C# 3.0, released with .NET Framework 3.5 in November 2007
2. Framework vs Language versions are different - .NET Framework 3.5 contained C# 3.0, not a separate language version
3. Use correct version numbers when searching: C# 1.0 through C# 12.0 are the official language versions
4. Modern releases follow .NET versioning: .NET 5+ aligns C# and .NET version numbers
5. Search strategically using version-specific terms like “C# 8.0 features” instead of framework-based terms

If you’re searching for information about a specific C# feature and can’t find it, try using the correct C# language version number in your search terms. This will lead you to the accurate documentation you need while avoiding the confusion caused by the .NET Framework 3.5 vs. C# 3.0 misunderstanding.