If you’ve been following my recent blog posts, you’re aware that I recently kicked off my personal journey learning Flutter and, consequently, Dart. This is not a professional endeavor - rather, it’s a way to augment my skills in cross-platform development while learning a new framework and language at the same time.

In this post I’ll delve into a comparison between Dart and C# as programming languages. This is a foundational post, so it’s just the beginning of the comparison and I won’t go deep into every detail. However, I’ll try to show why some aspects of Dart are important for Flutter development. Making a direct comparison to C# is my way of easing into Dart - using my 15+ years professional experience with C# and the .NET ecosystem to facilitate comprehension and learning.

Despite many years in that ecosystem, I’ve been away from daily C# programming for the last 3 years, and while I try to keep myself up-to-date, please excuse me if there are any aspects of more recent features that I might be unaware of.

Historical Context

Let’s begin with a myth breaker: Dart is NOT a dynamically typed language. That reputation comes from Dart’s early versions, where the type system existed but type annotations were optional and not enforced. Code could compile and run even with type mismatches, giving it a “dynamic” feel in practice.

Since version 2.0 (released in 2018), this changed completely. Today, like C#, Dart is statically and strongly typed with compile-time type checking that catches type errors before your code runs.

Paradigms and Structure

C# has always been known as an Object-Oriented Programming (OOP) language, and that’s absolutely true. However, that doesn’t mean it lacks features from other paradigms. Modern C# embraces functional programming concepts extensively. LINQ and lambdas arrived in .NET 3.5, with LINQ being the standout feature of that release.More recent versions continued this trend: pattern matching (C# 7+) and records with immutable data structures (C# 9) fundamentally changed how we write C# code today.

Dart follows a similar path. It’s primarily an OOP language but also incorporates functional programming features. A key structural difference: unlike C#, where code traditionally lives inside classes, Dart treats functions as first-class citizens. You can write standalone functions at the top level, pass them as parameters, and store them in variables-no static class wrappers needed.

Traditional C# approach:

public static class StringUtils
{
    public static string Capitalize(string input) 
        => char.ToUpper(input[0]) + input.Substring(1);
}

var result = StringUtils.Capitalize("hello");

Dart approach:

// Top-level function - no class needed
String capitalize(String input) 
    => input[0].toUpperCase() + input.substring(1);

// Functions as first-class citizens
final transformer = capitalize;
final names = ['alice', 'bob'].map(capitalize).toList();

This structural flexibility becomes particularly useful in Flutter development, where you often need utility functions, helper methods, or pure transformations that don’t conceptually belong to any class.

Type System & Null Safety

As I’ve already stated above, both C# and Dart are statically and strongly typed, compile-time checked languages. But there are some fundamental similarities and differences in how type inference and null safety work in each language.

Starting with type inference, this is where the similarities reside. Both languages have aggressive type inference, so while you can optionally declare the type of a variable, the compiler is able to infer it from the assigned value. However, explicitly declaring types is more common in C# codebases, particularly when the type isn’t immediately obvious from the assignment.

C# variable declaration:

// Type inference when assignment is explicit
var name = "John Doe";

// Explicit type when return value isn't obvious
double result = Calculator.Add(x, y);

Dart variable declaration:

// Compiler infers String type
var name = "John Doe";

// Valid but less idiomatic Dart
String name = "John Doe";

As you can see, there are no syntax differences between both languages regarding type inference. Things become more interesting when it comes to null safety. Let’s look at two snippets and think about what happens before reading further.

C# null approach:

string firstName = null;
string? lastName = null;

Dart null approach:

String firstName = null;
String? lastName = null;

First thing you likely noticed: the snippets look nearly identical. I could have written String with a capital ‘S’ for C# as well, since it’s just syntactic sugar for the System.String reference type. However, I didn’t because lowercase string is the idiomatic C# style, and I wanted to highlight this small naming convention difference between the languages.

But let’s focus on what matters: what happens on each line?

In C#, it depends. While the code is syntactically valid, the first line will cause a compiler error if nullable reference types are enabled (available since C# 8.0, 2019). This feature makes it impossible to assign null to a variable unless you explicitly mark it nullable with the ? modifier. However, this is an opt-in feature that must be enabled in your project. It’s very common to still see codebases with this feature disabled, especially in legacy systems where the migration effort to add nullable annotations and address all warnings would be tremendous and often not worthwhile.

In Dart, the first line is always an error. Not because a feature might be enabled, but because you don’t have that option at all. Sound null safety has been mandatory since Dart 2.12 (2021)—you cannot opt out. This makes Dart code inherently more reliable and reduces the need for defensive null checks that often litter pre-nullable-reference-types C# codebases.

Modifiers: var/final/const

Let’s end this foundational post with a comparison of variable modifiers. Dart has essentially three modifiers you can use when declaring a variable: var, final, and const. C# has, respectively, var, readonly, and const. I intentionally use the word “respectively” because these are indeed equivalent in functionality.

Dart C# Description
var var Declares mutable variables
final readonly Declares immutable variables (evaluated at runtime)
const const Compile-time constants (evaluated at compile-time)

Like in C#, the Dart compiler performs replacement of const variables everywhere they’re used in the code. Consider this snippet:

const something = "some value";
var foo = something;
var bar = something;

During compilation, this effectively becomes:

// The const declaration is evaluated and inlined throughout the code
var foo = "some value";
var bar = "some value";

However, here’s where Dart diverges significantly from C#: const works with complex objects, not just primitives.

// This raises a compile-time error - only primitives like strings or integers are allowed
const int[] numbers = { 1, 2, 3 };

// Perfectly valid Dart code
const itWorks = [1, 2, 3];

This becomes crucial in Flutter development. Consider these two approaches:

// Without const - new instance created every rebuild
Container(
  width: 100,
  height: 100,
  color: Colors.blue,
)

// With const - single instance shared across all rebuilds
const Container(
  width: 100,
  height: 100,
  color: Colors.blue,
)

The difference is substantial. Without const, Flutter creates a new Container instance in memory every time the widget tree rebuilds (which can happen frequently during animations, state changes, or user interactions). With const, the compiler creates a single instance at compile-time that’s reused across all widget builds, significantly reducing memory allocations and improving performance.

This is one area where Dart’s const is more powerful than C#’s equivalent—you can mark entire widget trees as const, something impossible with C#’s restrictions on constant expressions.

Conclusion

While apparently similar in both features and syntax, Dart and C# do have some key differences that are essential to understand for effective Flutter development. As an experienced C# developer, overlooking these fundamental distinctions can impact not only application runtime performance but also the overall developer experience—making it harder to write idiomatic code, maintain clarity, and troubleshoot issues in Flutter codebases.

That said, the similarities make the transition smoother than you might expect. And to be honest, learning this stuff is always fun!

In the next post, I’ll likely dive deeper into object-oriented programming in Dart—exploring how visibility modifiers work (spoiler: no public or private keywords!), interesting commonalities with C#, and some Dart-specific features that might surprise you.

See you in the next post.