csharp-godot

C# in Godot 4.3+

This skill covers C#-specific conventions, API differences from GDScript, project setup, and interop patterns. All examples are C# only. Target Godot 4.3+ with the GodotSharp NuGet package.

Related skills: csharp-signals for C# signal patterns, godot-project-setup for C# project scaffolding, godot-testing for C# testing with gdUnit4.

---

1. C# vs GDScript Syntax Comparison

GDScript	C# Equivalent	Notes
var x = 5	var x = 5; or typed int x = 5;	C# var infers type at compile time
func MyMethod() -> void:	public void MyMethod() { }	Methods are PascalCase in C#
signal health_changed(amount: int)	[Signal] delegate void HealthChangedEventHandler(int amount);	Must use EventHandler suffix
@export var speed: float = 100.0	[Export] public float Speed { get; set; } = 100f;	PascalCase, property syntax
@onready var label = $Label	private Label _label; + _label = GetNode<Label>("Label"); in _Ready()	No @onready equivalent; use _Ready()
match value:	switch (value) { case X: break; }	C# switch also supports pattern matching
class_name MyClass	[GlobalClass] public partial class MyClass : GodotObject { }	Requires [GlobalClass] attribute
extends Node	public partial class MyScript : Node { }	Inheritance via :
preload("res://scene.tscn")	GD.Load<PackedScene>("res://scene.tscn")	Loaded at runtime, not compile time
push_error("msg")	GD.PushError("msg");	Prints to Godot error log
print("msg")	GD.Print("msg");	Also: GD.PrintS(), GD.PrintT()
node is CharacterBody2D	node is CharacterBody2D	Same keyword, same semantics
node as CharacterBody2D	node as CharacterBody2D	Returns null on failure in both
await signal_name	await ToSignal(source, SignalName.X);	Must use ToSignal() wrapper
Array	Godot.Collections.Array	Not System.Collections.Generic.List<T>
Dictionary	Godot.Collections.Dictionary	Not System.Collections.Generic.Dictionary<K,V>

---

2. Project Setup

.csproj and Solution

Godot auto-generates the .csproj when you create the first C# script via Script > New Script > C#. Do not edit the generated file structure manually — let the editor manage it.

MyProject/
├── MyProject.csproj          # Auto-generated, edit only for NuGet packages
├── MyProject.sln             # Auto-generated solution file
├── project.godot
└── scripts/
    └── Player.cs

NuGet Packages

Add packages in MyProject.csproj inside <ItemGroup>:

<Project Sdk="Godot.NET.Sdk/4.3.0">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <Nullable>enable</Nullable>
    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
  </PropertyGroup>
  <ItemGroup>
    <!-- Example: add a third-party NuGet package -->
    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
  </ItemGroup>
</Project>

Run dotnet restore or let the IDE restore automatically after editing.

IDE Setup

IDE	Setup Required	Notes
JetBrains Rider	Install Godot plugin (bundled in Rider 2023.3+)	Best Godot C# support; debugger works out of the box
VS Code	Install C# Dev Kit + Godot Tools extensions	Requires launch.json for debugger attachment
Visual Studio	Install Godot Visual Studio extension	Windows only; debugger via Tools > Attach to Process

For all IDEs, open the .sln file (not just a folder) to get full solution resolution.

---

3. The partial class Requirement

Every class that extends a Godot type must be declared partial. This is not optional.

Why

Godot uses C# source generators to emit the signal registration, property binding, and RPC code alongside your class. Source generators require partial to inject into the same class declaration.

Error When Forgotten

Error CS0260: Missing partial modifier on declaration of type 'Player';
another partial declaration of this type exists.

Or the class compiles but signals and [Export] properties silently fail to register.

Rule

// CORRECT
public partial class Player : CharacterBody2D { }

// WRONG — will cause source generator errors
public class Player : CharacterBody2D { }

This applies to every class in the inheritance chain that extends a Godot type, including intermediate base classes.

---

4. Naming Conventions

Element	Convention	Example
Methods	PascalCase	public void TakeDamage(int amount)
Properties	PascalCase	public float MaxHealth { get; set; }
Signals (delegate)	PascalCase + EventHandler suffix	HealthChangedEventHandler
[Export] properties	PascalCase	[Export] public float Speed { get; set; }
Private fields	_camelCase with underscore prefix	private float _currentSpeed;
Local variables	camelCase	var newPosition = ...
Parameters	camelCase	void SetHealth(int newHealth)
Godot API names	Match Godot's PascalCase exactly	GlobalPosition not global_position
Enums	PascalCase type, PascalCase members	enum State { Idle, Running, Dead }
Constants	PascalCase or SCREAMING_SNAKE per team style	const float MaxSpeed = 200f;

Always match GodotSharp property and method names exactly — they are PascalCase translations of the GDScript snake_case names (e.g. is_on_floor() → IsOnFloor()).

---

5. Signals in C#

Signals require a delegate declaration with the [Signal] attribute. The delegate name must end with EventHandler.

using Godot;

public partial class Player : CharacterBody2D
{
    // Declaration
    [Signal] public delegate void HealthChangedEventHandler(int newHealth);
    [Signal] public delegate void DiedEventHandler();

    private int _health = 100;

    public void TakeDamage(int amount)
    {
        _health -= amount;
        EmitSignal(SignalName.HealthChanged, _health);  // Use SignalName.X, not a string
        if (_health <= 0)
            EmitSignal(SignalName.Died);
    }
}

Connecting and Disconnecting

// Connect with +=
player.HealthChanged += OnHealthChanged;
player.Died += OnPlayerDied;

// Disconnect with -=
player.HealthChanged -= OnHealthChanged;
player.Died -= OnPlayerDied;

// Handler signatures must match the delegate
private void OnHealthChanged(int newHealth) { ... }
private void OnPlayerDied() { ... }

For full signal patterns including one-shot connections, static typed signals, and cross-language signal wiring, see the csharp-signals skill.

---

6. Async / Await

GDScript's await maps to C#'s await ToSignal(...). Godot signals return a SignalAwaiter that is compatible with C# await.

Awaiting a Godot Signal

public async void StartCutscene()
{
    // Wait for a timer to finish
    await ToSignal(GetTree().CreateTimer(2.0), Timer.SignalName.Timeout);

    // Wait for an animation to finish
    var anim = GetNode<AnimationPlayer>("AnimationPlayer");
    anim.Play("intro");
    await ToSignal(anim, AnimationPlayer.SignalName.AnimationFinished);

    GD.Print("Cutscene complete");
}

Task-Based Patterns

For CPU-bound work, use Task.Run — but never touch Godot objects from a non-main thread:

public async void LoadHeavyData()
{
    // Off main thread: pure C# computation only
    var result = await Task.Run(() => ComputeSomethingExpensive());

    // Back on main thread: safe to use Godot API
    ApplyResult(result);
}

private int ComputeSomethingExpensive()
{
    // No Godot API calls here
    return Enumerable.Range(0, 1_000_000).Sum();
}

GDScript await Equivalents

GDScript	C#
await get_tree().create_timer(1.0).timeout	await ToSignal(GetTree().CreateTimer(1.0), Timer.SignalName.Timeout)
await animation_player.animation_finished	await ToSignal(animPlayer, AnimationPlayer.SignalName.AnimationFinished)
await signal_name	await ToSignal(this, SignalName.YourSignal)

---

7. GDScript Interop

Calling GDScript from C#

Use Call, Get, and Set on any GodotObject. Values are marshalled through Variant.

// Assume "enemy" is a GodotObject backed by a GDScript with func take_damage(amount)
GodotObject enemy = GetNode("Enemy");

// Call a GDScript method
enemy.Call("take_damage", 25);

// Get a GDScript property
float health = enemy.Get("health").AsSingle();

// Set a GDScript property
enemy.Set("is_stunned", true);

Calling C# from GDScript

If a C# class is registered as a [GlobalClass], GDScript can instantiate and use it directly without any extra wiring:

[GlobalClass]
public partial class WeaponData : Resource
{
    [Export] public float Damage { get; set; } = 10f;
    [Export] public float Cooldown { get; set; } = 0.5f;
}

# GDScript — works because WeaponData is a [GlobalClass]
var data := WeaponData.new()
data.damage = 50.0

Non-[GlobalClass] C# types are not visible to GDScript by name but can still be passed as Variant/Object references.

Variant Marshalling Gotchas

Scenario	Issue	Fix
Passing null across boundary	GDScript null becomes default(Variant), not C# null	Check variant.VariantType == Variant.Type.Nil
Returning int[] from C#	GDScript receives a PackedInt32Array, not an Array	Return Godot.Collections.Array<int> for consistent typing
Passing System.Collections.Generic.List<T>	Not marshallable — Godot doesn't know this type	Convert to Godot.Collections.Array<T> first
Godot Color struct	Passed by value through Variant correctly	No issue

---

8. Performance

C# vs GDScript

Workload	Winner	Reason
Math-heavy loops (pathfinding, simulation)	C# (significantly faster)	Compiled JIT vs interpreted GDScript
Large array/collection processing	C#	Value type arrays avoid boxing
Godot API calls (move_and_slide, etc.)	Roughly equal	Both route through the same C++ engine
Scene tree operations	Roughly equal	Bottleneck is C++ overhead, not language
Rapid prototyping	GDScript	Less boilerplate, hot-reload without recompile
Editor tooling (plugins, @tool)	GDScript	C# tool scripts require a full build cycle

Guidance

• Use C# for systems with tight loops: physics solvers, procedural generation, AI decision trees, data processing.
• Use GDScript for editor plugins, @tool scripts, and rapid iteration on gameplay logic.
• Mixing languages in the same project is supported — interop cost is minimal for occasional cross-language calls.
• Avoid Godot.Collections.Array for hot paths; prefer typed arrays (Array<T>) or native C# arrays (T[]) converted at boundaries.
• StringName lookups are O(1) but StringName construction is not — cache them if created frequently.

---

9. Common Gotchas

Gotcha	Problem	Fix
Variant to C# type conversion	(float)someVariant throws if the underlying type is int	Use .AsSingle(), .AsInt32(), etc. instead of casts
null vs default(Variant)	Godot signals passing no value give default(Variant), not C# null	Check .VariantType == Variant.Type.Nil
Godot.Collections vs System.Collections	Godot API methods return Godot.Collections.Array; passing List<T> causes runtime error	Always use Godot.Collections.Array/Dictionary at Godot API boundaries
Disposing native objects	Calling methods on a freed Godot object throws ObjectDisposedException	Check IsInstanceValid(obj) before use
StringName construction in hot loops	new StringName("my_signal") allocates each call	Cache as private static readonly StringName _signalName = "my_signal";
Export array types	[Export] public Array Items; exports untyped array	Use [Export] public Godot.Collections.Array<MyResource> Items { get; set; }
Node path strings	GetNode("../UI/Label") fails silently if the path changes	Use GetNode<Label>("%Label") with unique names or typed [Export] node references
partial class forgotten	Source generators silently fail; [Export] and [Signal] don't register	Every class extending a Godot type must be partial
async void vs async Task	async void swallows exceptions	Use async Task except for top-level event handlers that Godot calls

---

10. Checklist

• Every class extending a Godot type is declared partial
• Method names match GodotSharp PascalCase (e.g. _Ready, _PhysicsProcess, IsOnFloor())
• [Export] properties are PascalCase and use property syntax ({ get; set; })
• Signal delegates end with EventHandler and use EmitSignal(SignalName.X)
• Signals connected with += and disconnected with -= when no longer needed
• await ToSignal(...) used for Godot signals — not raw Task.Delay for game timing
• Godot.Collections.Array/Dictionary used at Godot API boundaries, not System.Collections types
• IsInstanceValid(obj) checked before using any potentially freed Godot object
• StringName instances cached if constructed in loops or frequently called methods
• No Godot API calls inside Task.Run(...) callbacks — all engine calls happen on the main thread
• .csproj opened via the .sln file in the IDE for full solution resolution
• C# used for computation-heavy systems; GDScript retained for editor tooling and @tool scripts