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, gdextension for native C++ when C# is not enough, multithreading for C# concurrency.

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>:

xml
<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.

Godot.NET Preview Bindings (Godot 4.7+)

Godot 4.7's Godot.NET.Sdk accepts an opt-in MSBuild property that switches the project from the classic GodotSharp bindings to the preview Godot.NET bindings (the Godot.Bindings assembly instead of GodotSharp):

xml
<PropertyGroup>
  <EnableGodotDotNetPreview>true</EnableGodotDotNetPreview>
</PropertyGroup>

The preview bindings are experimental — leave the property unset for production projects. See GH-118001.

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

csharp
// 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.

csharp
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

csharp
// 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

csharp
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:

csharp
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.

csharp
// 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:

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

gdscript
# 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 |

> ⚠️ Changed in Godot 4.7: The 4.7 C# assemblies ship several compatibility breaks. Binary-incompatible only (source still compiles — a rebuild suffices): OptimizedTranslation.Generate() now returns bool instead of void (GH-119563). Binary- and source-incompatible (code changes required): Animation.Length changed type metadata from float to double (GH-116394) — the C# property is now double, so float len = anim.Length; no longer compiles — and Control.AccessibilityLive changed enum type from DisplayServer.AccessibilityLiveMode to AccessibilityServer.AccessibilityLiveMode (GH-116839) — update declarations to the AccessibilityServer enum. Source-incompatible (existing binaries still load): RichTextLabel.ImageUpdateMask.UpdateWidthInPercent was renamed to UpdateWidthUnit (GH-112617), and the EditorSceneFormatImporter IMPORT_* constants moved into the ImportFlags enum (GH-115788). Removed: AudioEffectSpectrumAnalyzer.TapBackPos (GH-114355). Rebuild against 4.7 and fix the affected symbols. See the 4.7 migration guide.

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