Rust for C# Developers

If you write C# for a living, good news: a lot of Rust will feel familiar. Rust has generics with constraints, async/await, powerful pattern matching, iterator chains that read a lot like LINQ, and one excellent command-line tool (Cargo) that does what dotnet does. You already know how to think in types, interfaces, and lambdas. That knowledge carries over.

The big shift is about memory and errors. Rust has no garbage collector. Instead, every value has one owner, and the compiler checks ownership and borrowing before your program runs. Rust also has no null (you use Option) and no exceptions (you use Result). These three changes are where most of your learning time will go. This page maps what you know from C# and .NET to Rust, so you can spend that time on the parts that are really new.

If you want a general comparison with C++, Go, and Python instead, see Rust vs Other Languages.

Language concepts: C# to Rust

Use this table as a phrase book. The last column links to the lesson on this site that explains the Rust side.

C#	Rust	Learn more
class with fields and methods	struct for the data + an impl block for the methods	Structs
interface	trait	Traits
Abstract class, inheritance	No inheritance. Use composition (a struct inside a struct) + traits with default methods	Traits, Design Patterns
List<IShape> of different classes	Vec<Box<dyn Shape>> (a trait object)	Trait Objects
Extension methods	Your own trait, implemented for a type you didn’t write (like String)	Traits
Generics with where T : IComparable<T>	Generics with trait bounds: T: Ord or where T: Ord	Generics
null, Nullable<int>, nullable reference types	Option<T>: either Some(value) or None	Option
?? and ?.	.unwrap_or(...), .map(...), .and_then(...), and ?	Option
Exceptions, throw, try/catch	Result<T, E> + the ? operator	Result, Custom Errors
An exception for a real bug (like InvalidOperationException)	panic! (stops the thread)	Panic
IDisposable + using	Drop, which runs automatically when the owner goes out of scope (RAII)	Scope, Smart Pointers
Garbage collector	Ownership and borrowing, checked at compile time	Ownership, Borrowing
record	struct with #[derive(Debug, Clone, PartialEq)]	Structs, Common Traits
with expression on a record	Struct update syntax: Order { total: 5, ..old }	Structs
enum (named integers only)	enum where each variant can carry its own data	Enums
switch expressions, is patterns	match (the compiler checks you covered every case)	match, Pattern Matching
Tuples (int, string)	Tuples (i32, String)	Tuples
ref / out parameters	&mut T, or return a tuple or an Option	Borrowing
Lambdas, Func<T>, Action<T>, delegates	Closures, described by the traits Fn, FnMut, FnOnce	Closures, Fn, FnMut & FnOnce
event	A channel, or a list of boxed closures (callbacks)	Channels, Fn, FnMut & FnOnce
LINQ: Where, Select, Sum, OrderBy, ToList	Iterator adapters: filter, map, sum, sort_by (on a Vec), collect	Iterators, Sorting
IEnumerable<T> and yield return	impl Iterator<Item = T>, or your own type that implements Iterator	Custom Iterators
async Task<T> / await	async fn returns a Future; you need a runtime like tokio to run it	Async/Await
Task.Run, Thread, lock	std::thread::spawn or tokio::spawn; Mutex<T> wraps the data it protects	Concurrency, Shared State
Properties (get; set;)	No properties. Use pub fields, or getter and setter methods	Structs
string and StringBuilder	&str (a borrowed view of text) and String (owned, growable)	Strings
String interpolation $"Hi {name}"	format!("Hi {name}") and println!("Hi {name}")	Output
var	let (immutable by default; write let mut to allow changes)	Variables
const, readonly	const, and plain let (already read-only)	Variables
static readonly field	static, or LazyLock for values built at startup	Variables
namespace and using directives	Modules (mod) and use	Modules
Assembly / project	Crate (a library or a binary)	Cargo & Crates
Attributes like [Serializable]	Attributes like #[derive(Serialize)] and derive macros	Macros, Serde & JSON
Reflection	Mostly none at runtime. Macros and derive generate code at compile time instead	Macros
unsafe and pointers	unsafe blocks and raw pointers	Unsafe Rust
Span<T>, ReadOnlySpan<char>	Slices: &[T] and &str	Slices
ToString() override, IFormattable	Implement Display (then .to_string() works for free)	Common Traits
IEquatable<T>, IComparable<T>, GetHashCode	PartialEq/Eq, PartialOrd/Ord, Hash (usually derived)	Common Traits
implicit / explicit conversion operators	From/Into (and TryFrom when it can fail)	Conversions
Operator overloading (operator +)	Implement traits from std::ops, like Add	Advanced Traits
checked / unchecked arithmetic	checked_add, wrapping_add, saturating_add	Integer Overflow
decimal	No built-in decimal type; use the rust_decimal crate, or store cents in an integer	Data Types

Collections

The standard library covers almost everything in System.Collections.Generic. Names change, ideas don’t.

C#	Rust	Learn more
List<T>	Vec<T>	Vectors
T[] (fixed length)	[T; N] when the length is known at compile time, otherwise Vec<T>	Arrays
Dictionary<K, V>	HashMap<K, V>	HashMaps
SortedDictionary<K, V>	BTreeMap<K, V> (keys stay sorted)	HashMaps
HashSet<T>	HashSet<T>	HashSet
SortedSet<T>	BTreeSet<T>	HashSet
Queue<T>	VecDeque<T> (push_back / pop_front)	VecDeque & BinaryHeap
Stack<T>	Vec<T> with push / pop	Vectors
PriorityQueue<TElement, TPriority>	BinaryHeap<T> (largest first; wrap in Reverse for smallest first)	VecDeque & BinaryHeap
LinkedList<T>	LinkedList<T> exists, but you rarely need it; VecDeque is usually faster	VecDeque & BinaryHeap
ConcurrentDictionary<K, V>	Mutex<HashMap<K, V>>, or the dashmap crate	Shared State

One thing to watch: like Dictionary, a Rust HashMap has no fixed order. If you print its contents, sort them first or use a BTreeMap.

Tooling: dotnet to cargo

This is the part most C# developers enjoy right away. Cargo does the jobs of the dotnet CLI, MSBuild, and NuGet in one tool.

.NET	Rust	Notes
dotnet CLI	cargo	Builds, runs, tests, adds packages, publishes. See Cargo & Crates
.csproj	Cargo.toml	Short and hand-editable
packages.lock.json	Cargo.lock	Created for you
.sln with several projects	A Cargo workspace	One Cargo.toml at the top lists the member crates
NuGet / nuget.org	crates.io	Every published crate’s API docs are on docs.rs
dotnet add package Serilog	cargo add tracing
dotnet new console	cargo new my_app (cargo new --lib for a library)
dotnet run / build / test	cargo run / cargo build / cargo test
-c Release	--release	Debug builds are much slower at runtime; benchmark in release
dotnet watch	cargo watch or bacon (installed with cargo install)
dotnet tool install -g	cargo install
global.json (SDK version)	rustup and a rust-toolchain.toml file
Roslyn analyzers	cargo clippy	Hundreds of helpful lints, official
dotnet format	cargo fmt	One standard style for everyone
Visual Studio / Rider	VS Code + rust-analyzer, or JetBrains RustRover	rust-analyzer gives completion, go-to-definition, and inline errors
XML doc comments ///	/// doc comments in Markdown + cargo doc	Code examples in docs are run as tests. See Documentation
xUnit / NUnit / MSTest	Built-in #[test] and cargo test (cargo nextest is a popular faster runner)	See Testing
Moq	mockall, or hand-written fakes that implement your trait
Coverlet (code coverage)	cargo llvm-cov or cargo tarpaulin
BenchmarkDotNet	criterion	See Performance
dotnet-trace, profilers	cargo flamegraph, perf, or any native profiler

Here is a small Cargo.toml, so you can compare it with a .csproj:

[package]
name = "orders-api"
version = "0.1.0"
edition = "2021"

[dependencies]
serde = { version = "1", features = ["derive"] }
serde_json = "1"
tokio = { version = "1", features = ["full"] }

Libraries and frameworks: “What do we use instead of…?”

This is the question every .NET team asks first. “We use Entity Framework. What do we have in Rust?” Here are the closest equivalents. Rust has no single company behind a “default stack” the way .NET has Microsoft, so you often pick between two or three good community crates.

Data access

.NET	Rust	Notes
Entity Framework Core	Diesel: ORM and query builder; your queries are type-checked at compile time. Migrations with diesel_cli	Mature (2.x), synchronous by default (diesel-async exists)
Entity Framework Core (async, entity-style)	SeaORM: async ORM with entities, relations, and migrations (sea-orm-cli)	Feels closest to EF; built on top of sqlx
Dapper	sqlx: you write plain SQL, and the query! macro checks it against your real database at compile time. Migrations with sqlx-cli	Async, very popular, not an ORM
ADO.NET	sqlx, tokio-postgres, rusqlite (SQLite)	Lower-level drivers
StackExchange.Redis	redis

If you liked EF, try SeaORM first. If you liked Dapper and writing your own SQL, try sqlx. If you want the strongest compile-time guarantees, try Diesel. Rust Databases shows all three with working code.

Web and networking

.NET	Rust	Notes
ASP.NET Core Web API	axum (we build one in Project: Web API), actix-web, Rocket	axum and actix-web are widely used in production
Minimal APIs	axum: routes are plain async fn handlers	The style is very close
Middleware pipeline	tower layers and the tower-http crate (CORS, compression, tracing, timeouts)	axum uses tower directly
Built-in dependency injection	State in axum, plain constructors, and traits	See the DI row below
Swashbuckle / OpenAPI	utoipa
SignalR	WebSockets in axum (the ws feature), or tokio-tungstenite	No SignalR-style protocol layer built in
gRPC (Grpc.AspNetCore)	tonic (with prost for protobuf)
HttpClient	reqwest	Async by default, with an optional blocking client
JWT bearer auth	jsonwebtoken

Everyday building blocks

.NET	Rust	Notes
System.Text.Json / Newtonsoft.Json	serde + serde_json	The standard; also does TOML, YAML, and more. See Serde & JSON
ILogger / Serilog	tracing (+ tracing-subscriber), or log + env_logger	Structured logging with spans. See Logging
IConfiguration / appsettings.json	config or figment	Layer files and environment variables, then deserialize with serde
DI container (IServiceCollection)	Usually nothing: pass dependencies into constructors, use traits for things you want to swap in tests	shaku exists, but few projects use a container
AutoMapper	Write From / Into implementations	Explicit and checked by the compiler. See Conversions
FluentValidation / DataAnnotations	validator or garde (derive-based validation)
Polly (retries)	backon, or tower’s retry middleware
MediatR	No direct equivalent	Plain traits, or channels between tasks
Hangfire / background jobs	tokio::spawn for in-process tasks; apalis for persistent job queues
CancellationToken	Drop the future, or use CancellationToken from tokio-util

Desktop, games, and more

.NET	Rust	Notes
Blazor WebAssembly	Leptos, Yew, Dioxus	All before version 1.0; APIs still change. See WebAssembly
WPF / WinForms / MAUI	Tauri (web UI + Rust backend), Slint, egui, Iced	Tauri 2 and Slint 1.x are the most stable. No first-party GUI toolkit
Unity	Bevy, or Rust inside Godot with the godot crate	Bevy is pre-1.0 and breaks its API between releases
ML.NET	candle, burn, linfa	Much younger than Python’s ML tools
Azure SDK for .NET	The official Azure SDK for Rust: azure_core, azure_identity, azure_storage_blob, …	Covers fewer services than the .NET SDK

An honest word on maturity

For web APIs, database access, JSON, logging, CLI tools, and gRPC, Rust’s libraries are solid and used in production by many companies. GUI, game engines, machine learning, and enterprise “glue” (DI containers, mediators, job schedulers) are younger. They work, but expect fewer tutorials, more API changes between versions, and less “one obvious choice” than in .NET. Check Are We Web Yet? and Are We GUI Yet? for the current state.

Side by side: a class becomes a struct + impl

Let’s look at real code. Here is a small bank account in C#:

var account = new BankAccount("Ada", 100);
account.Deposit(50);
Console.WriteLine($"{account.Owner} has {account.Balance}");

public class BankAccount
{
    public string Owner { get; }
    private decimal balance;

    public BankAccount(string owner, decimal balance)
    {
        Owner = owner;
        this.balance = balance;
    }

    public void Deposit(decimal amount) => balance += amount;
    public decimal Balance => balance;
}

And in Rust:

struct BankAccount {
    owner: String,
    balance: i64,
}

impl BankAccount {
    // `new` is just a convention, not a keyword.
    fn new(owner: &str, balance: i64) -> Self {
        BankAccount { owner: owner.to_string(), balance }
    }

    // `&mut self`: this method changes the account.
    fn deposit(&mut self, amount: i64) {
        self.balance += amount;
    }

    // `&self`: this method only reads.
    fn balance(&self) -> i64 {
        self.balance
    }
}

fn main() {
    let mut account = BankAccount::new("Ada", 100);
    account.deposit(50);
    println!("{} has {}", account.owner, account.balance());
}

Output:

Ada has 150

▶ Try it Yourself

Data and behavior live in two separate blocks. There are no constructors, only functions that return Self. Every method says up front whether it reads (&self) or changes (&mut self) the value. And because deposit changes the account, the variable must be let mut. In C#, any method can change any field; in Rust, changes are visible in the signature.

Side by side: an interface becomes a trait

In C#, you might have an IShape interface with two classes and a List<IShape>:

var shapes = new List<IShape> { new Circle { Radius = 1 }, new Rectangle { Width = 2, Height = 3 } };
foreach (var s in shapes) Console.WriteLine($"{s.Area():F2}");

public interface IShape { double Area(); }

public class Circle : IShape
{
    public double Radius { get; init; }
    public double Area() => Math.PI * Radius * Radius;
}

public class Rectangle : IShape
{
    public double Width { get; init; }
    public double Height { get; init; }
    public double Area() => Width * Height;
}

In Rust, the interface is a trait, and each struct implements it in its own impl block:

trait Shape {
    fn area(&self) -> f64;
}

struct Circle {
    radius: f64,
}

struct Rectangle {
    width: f64,
    height: f64,
}

impl Shape for Circle {
    fn area(&self) -> f64 {
        std::f64::consts::PI * self.radius * self.radius
    }
}

impl Shape for Rectangle {
    fn area(&self) -> f64 {
        self.width * self.height
    }
}

fn main() {
    // Box<dyn Shape> plays the role of "a reference to some IShape".
    let shapes: Vec<Box<dyn Shape>> = vec![
        Box::new(Circle { radius: 1.0 }),
        Box::new(Rectangle { width: 2.0, height: 3.0 }),
    ];

    for shape in &shapes {
        println!("{:.2}", shape.area());
    }
}

Output:

3.14
6.00

▶ Try it Yourself

In C#, every interface call goes through a virtual call. In Rust you choose: Box<dyn Shape> uses a virtual call (see Trait Objects), while a generic function like fn print_area<T: Shape>(s: &T) is compiled separately for each type, with no virtual call at all. A nice extra: you can implement your own trait for types you didn’t write, even String or i32. That’s how Rust does what extension methods do in C#.

Side by side: null becomes Option

C# with nullable reference types warns you about null, but null still exists at runtime:

string? FindEmail(int userId) => userId == 1 ? "[email protected]" : null;

var email = FindEmail(2);
if (email is not null) Console.WriteLine(email.ToUpper());
else Console.WriteLine("no email on file");

Console.WriteLine(FindEmail(2) ?? "unknown");

In Rust, a value that might be missing has the type Option<T>. You can’t use it as a plain value until you’ve handled the None case:

fn find_email(user_id: u32) -> Option<String> {
    if user_id == 1 {
        Some("[email protected]".to_string())
    } else {
        None
    }
}

fn main() {
    match find_email(1) {
        Some(email) => println!("{}", email.to_uppercase()),
        None => println!("no email on file"),
    }

    // `if let` is the short form when you only care about one case.
    if let Some(email) = find_email(2) {
        println!("found {email}");
    } else {
        println!("no email on file");
    }

    // unwrap_or works like C#'s ?? operator.
    let email = find_email(2).unwrap_or("unknown".to_string());
    println!("{email}");
}

Output:

[email protected]
no email on file
unknown

▶ Try it Yourself

There is no NullReferenceException in Rust, because there is no null to dereference. The compiler simply won’t let you call .to_uppercase() on an Option<String>. Learn the helper methods on the Option page, and the short forms on if let.

Side by side: try/catch becomes Result and ?

In C#, parsing can throw, and you catch the exception somewhere up the call stack:

static int TotalSeats(string a, string b) => int.Parse(a) + int.Parse(b);

try
{
    Console.WriteLine(TotalSeats("12", "30"));
    Console.WriteLine(TotalSeats("12", "thirty"));
}
catch (FormatException e)
{
    Console.WriteLine($"Error: {e.Message}");
}

In Rust, a function that can fail says so in its return type. The ? operator means “if this failed, return the error to my caller right now”. It does the job of letting an exception bubble up, but you can see it in the code:

use std::num::ParseIntError;

fn total_seats(a: &str, b: &str) -> Result<i32, ParseIntError> {
    let first: i32 = a.parse()?;
    let second: i32 = b.parse()?;
    Ok(first + second)
}

fn main() {
    for (a, b) in [("12", "30"), ("12", "thirty")] {
        match total_seats(a, b) {
            Ok(total) => println!("Total: {total}"),
            Err(e) => println!("Error: {e}"),
        }
    }
}

Output:

Total: 42
Error: invalid digit found in string

▶ Try it Yourself

The big difference: in C#, any method might throw, and the signature doesn’t tell you. In Rust, Result is part of the signature, so callers can’t forget to handle it. For your own error types, see Custom Errors. In applications, the anyhow crate gives you something close to “catch any exception” (see anyhow & thiserror).

Side by side: LINQ becomes an iterator chain

A typical LINQ query:

var orders = new List<Order> { new("Ada", 120), new("Grace", 80), new("Linus", 200), new("Ken", 150) };

var bigSpenders = orders
    .Where(o => o.Total > 100)
    .OrderByDescending(o => o.Total)
    .Select(o => o.Customer)
    .ToList();

Console.WriteLine(string.Join(", ", bigSpenders));
Console.WriteLine($"Revenue: {orders.Sum(o => o.Total)}");

record Order(string Customer, int Total);

The Rust version uses iterator adapters and closures:

struct Order {
    customer: String,
    total: u32,
}

fn main() {
    let orders = vec![
        Order { customer: "Ada".to_string(), total: 120 },
        Order { customer: "Grace".to_string(), total: 80 },
        Order { customer: "Linus".to_string(), total: 200 },
        Order { customer: "Ken".to_string(), total: 150 },
    ];

    // Where(...).ToList()
    let mut big: Vec<&Order> = orders.iter().filter(|o| o.total > 100).collect();
    // OrderByDescending(...): sorting happens on a Vec, not on the iterator.
    big.sort_by(|a, b| b.total.cmp(&a.total));
    // Select(...)
    let names: Vec<&str> = big.iter().map(|o| o.customer.as_str()).collect();

    println!("{}", names.join(", "));

    // Sum(...)
    let revenue: u32 = orders.iter().map(|o| o.total).sum();
    println!("Revenue: {revenue}");
}

Output:

Linus, Ken, Ada
Revenue: 550

▶ Try it Yourself

Rust iterators are lazy, just like LINQ’s deferred execution: nothing runs until you call something like collect(), sum(), or a for loop. collect() is your ToList(). Unlike LINQ, iterator chains are usually compiled down to the same machine code as a hand-written loop, so you don’t pay for the nice style. Sorting is covered on the Sorting page.

Side by side: using/IDisposable becomes Drop

In C#, you must remember using to release a resource on time:

using (var conn = new Connection("orders-db"))
{
    Console.WriteLine($"querying {conn.Name}");
}
Console.WriteLine("after the block");

class Connection : IDisposable
{
    public string Name { get; }
    public Connection(string name) => Name = name;
    public void Dispose() => Console.WriteLine($"closing connection to {Name}");
}

In Rust, cleanup is automatic. When the owner of a value goes out of scope, Rust calls its Drop implementation. There is nothing to forget:

struct Connection {
    name: String,
}

impl Drop for Connection {
    fn drop(&mut self) {
        println!("closing connection to {}", self.name);
    }
}

fn main() {
    {
        let conn = Connection { name: "orders-db".to_string() };
        println!("querying {}", conn.name);
    } // `conn` goes out of scope here, so drop() runs.

    println!("after the block");
}

Output:

querying orders-db
closing connection to orders-db
after the block

▶ Try it Yourself

This is called RAII, and it’s how Rust handles everything: files, sockets, locks, and memory itself. A file closes when its File value is dropped. A Mutex unlocks when its guard is dropped. There is no finalizer and no GC pause; cleanup happens at a predictable moment.

Things that will trip you up as a C# developer

Everyone coming from C# hits the same bumps. Knowing them in advance helps.

• Assignment moves, it doesn’t copy a reference. In C#, var b = a; for a class gives you two references to one object. In Rust, let b = a; moves ownership of a String or Vec into b, and a can’t be used anymore:

  fn main() {
      let owner = String::from("Ada");
      let copy = owner;
      println!("{owner} and {copy}");
  }

  error[E0382]: borrow of moved value: `owner`
   --> src/main.rs:4:16
    |
  2 |     let owner = String::from("Ada");
    |         ----- move occurs because `owner` has type `String`, which does not implement the `Copy` trait
  3 |     let copy = owner;
    |                ----- value moved here
  4 |     println!("{owner} and {copy}");
    |                ^^^^^ value borrowed here after move

  The fix is to borrow (let copy = &owner;) or to clone on purpose (owner.clone()). Read Ownership first; it explains this rule.

• The borrow checker. You can have many readers (&T) or one writer (&mut T) at a time, never both. Patterns that are normal in C#, like objects that point back to their parent, or many objects changing one shared object, need smart pointers or a different design. Expect a few frustrating weeks. It gets much easier.

• String vs &str. C# has one string type. Rust has two: String owns its text, &str borrows it. Functions usually take &str and structs usually store String. See Strings.

• No inheritance. You can’t write a base class with shared fields and override methods. Use traits (with default methods) for shared behavior, and put shared data in a struct that other structs contain.

• No exceptions. Errors are values. You’ll write ? a lot, and your main can return Result too. Calling .unwrap() is fine while learning, but it’s the Rust version of “ignore the exception and crash”.

• No null. At first, Option everywhere feels like extra work. After a while you’ll notice that you’ve stopped getting null-reference bugs.

• Explicit clones. Rust never copies a heap value behind your back. If you see .clone(), a real copy is made. That’s a feature: the cost is visible.

• Compile times. A clean build of a project with many crates takes longer than a .NET build. Incremental builds and cargo check (which skips code generation) are much faster; use cargo check while you edit.

• Async needs a runtime. In .NET, the runtime and thread pool are always there. In Rust, an async fn does nothing until an executor runs it, so you add tokio and put #[tokio::main] on main. See Async/Await.

A learning path for C# developers

You don’t need to read this site in order. As a C# developer, this route skips what you already know and spends time where Rust is different:

1. Get Started: install Rust and run cargo new.
2. Variables and Data Types: skim these, mostly to learn let mut and the number types.
3. Ownership, then Borrowing, then Slices: the most important pages for you. Take your time.
4. Strings: String vs &str.
5. Structs and Enums, then match and Pattern Matching.
6. Option and Result, then Custom Errors.
7. Traits, Generics, Common Traits, and Trait Objects.
8. Closures and Iterators: your LINQ.
9. Vectors, HashMaps, and VecDeque & BinaryHeap.
10. Modules, Cargo & Crates, and Testing.
11. Lifetimes and Smart Pointers.
12. Concurrency, Shared State, and Async/Await.
13. Serde & JSON and Logging, then build the Web API project.

Practice

Both exercises give you a C# snippet. Port it to Rust.

1. Port a record and a LINQ query

Port this C# code. It should print the names of products that are in stock and cost less than 20. Hint: make a struct with #[derive(Debug, Clone, PartialEq)], then use filter, map, and collect into a Vec<&str>. Vec<&str> has a .join(", ") method.

var products = new List<Product>
{
    new("Notebook", 5, true),
    new("Headphones", 45, true),
    new("Pen", 2, false),
    new("Mug", 12, true),
};

var cheap = products.Where(p => p.InStock && p.Price < 20).Select(p => p.Name);
Console.WriteLine(string.Join(", ", cheap));

record Product(string Name, int Price, bool InStock);

Show solution

#[derive(Debug, Clone, PartialEq)]
struct Product {
    name: String,
    price: u32,
    in_stock: bool,
}

fn product(name: &str, price: u32, in_stock: bool) -> Product {
    Product { name: name.to_string(), price, in_stock }
}

fn main() {
    let products = vec![
        product("Notebook", 5, true),
        product("Headphones", 45, true),
        product("Pen", 2, false),
        product("Mug", 12, true),
    ];

    let cheap: Vec<&str> = products
        .iter()
        .filter(|p| p.in_stock && p.price < 20)
        .map(|p| p.name.as_str())
        .collect();

    println!("{}", cheap.join(", "));
}

Output:

Notebook, Mug

▶ Try it Yourself

A small helper function plays the role of the record’s positional constructor. The derives give you what a C# record gives you for free: printing with {:?}, copying with .clone(), and comparing with ==.

2. Port a Dictionary with exceptions

This C# code takes one item out of a stock dictionary and throws when something is wrong. Port it so that take returns a Result<u32, String> instead of throwing. Hint: stock.get_mut(item) returns an Option<&mut u32>. Turn it into a Result with .ok_or(...), then use ?.

var stock = new Dictionary<string, int> { ["apples"] = 3, ["pears"] = 0 };

int Take(string item)
{
    if (!stock.TryGetValue(item, out var count))
        throw new KeyNotFoundException($"no item called {item}");
    if (count == 0)
        throw new InvalidOperationException($"{item} is out of stock");
    stock[item] = count - 1;
    return count - 1;
}

foreach (var item in new[] { "apples", "pears", "kiwis" })
{
    try { Console.WriteLine($"took one {item}, {Take(item)} left"); }
    catch (Exception e) { Console.WriteLine($"error: {e.Message}"); }
}

Show solution

use std::collections::HashMap;

fn take(stock: &mut HashMap<String, u32>, item: &str) -> Result<u32, String> {
    let count = stock
        .get_mut(item)
        .ok_or(format!("no item called {item}"))?;

    if *count == 0 {
        return Err(format!("{item} is out of stock"));
    }

    *count -= 1;
    Ok(*count)
}

fn main() {
    let mut stock = HashMap::new();
    stock.insert("apples".to_string(), 3);
    stock.insert("pears".to_string(), 0);

    for item in ["apples", "pears", "kiwis"] {
        match take(&mut stock, item) {
            Ok(left) => println!("took one {item}, {left} left"),
            Err(e) => println!("error: {e}"),
        }
    }
}

Output:

took one apples, 2 left
error: pears is out of stock
error: no item called kiwis

▶ Try it Yourself

TryGetValue with an out parameter becomes get_mut, which returns an Option. The two throws become Err values, and the try/catch becomes a match. The &mut stock in the call makes it clear that take changes the dictionary.

Recap

• Much of C# carries over: generics, async/await, lambdas, pattern matching, and LINQ-style iterators all have close Rust equivalents.
• The big shifts are ownership instead of a garbage collector, Option instead of null, and Result + ? instead of exceptions.
• Classes become a struct + impl, interfaces become traits, and inheritance becomes composition plus traits. using/IDisposable becomes automatic Drop.
• Cargo replaces the dotnet CLI, MSBuild, and NuGet; clippy and rustfmt replace analyzers and dotnet format; testing is built in.
• For EF Core look at SeaORM or Diesel, for Dapper look at sqlx, and for ASP.NET Core look at axum or actix-web. GUI, games, and ML options are younger.

Quick check

Quick check

1. What does Rust use instead of null?

A special nil keyword Option<T>, with Some(value) or None Nullable reference types, like C# An empty string

2. Your team uses Dapper and likes writing SQL by hand. Which Rust crate is the closest match?

serde Bevy tonic sqlx

3. What is the closest Rust equivalent of C#'s using block with IDisposable?

Drop, which runs automatically when the owner goes out of scope A finally block Calling free() by hand Rust has no way to clean up resources

4. In C#, var b = a; with a class copies a reference. What does let b = a; do with a String in Rust?

It copies the reference, like C# It makes a deep copy automatically It moves ownership to b, so a can no longer be used It is a compile error

Score: 0 / 4

Read more

• Rust for C#/.NET Developers — Microsoft: Microsoft’s own guide, with many more side-by-side C# and Rust examples.
• The Rust Programming Language: the official book. Chapters 4 (ownership), 9 (errors), and 10 (generics and traits) matter most for C# developers.
• Getting Started with Diesel and SeaORM documentation: the two main ORMs, if you’re looking for Entity Framework.
• sqlx on docs.rs: the Dapper-style choice, with compile-time checked SQL.
• Are We Web Yet? and Are We GUI Yet?: community overviews of Rust’s web and desktop GUI libraries.