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

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.

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):

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

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

IDE Setup

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 GD0001: Missing partial modifier on declaration of type 'Player'
that derives from 'Godot.GodotObject'

The build fails, so a missing partial cannot slip through.

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

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), SceneTreeTimer.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

7. GDScript Interop

C# calls into GDScript objects with Call, Get, and Set, and GDScript can use a C# class directly when it is registered as a [GlobalClass]. Values cross the boundary as Variant, and the reference lists the marshalling gotchas (null, int[], List<T>).

See references/gdscript-interop.md for the Call/Get/Set examples, the [GlobalClass] pattern, and the Variant marshalling table.

8. Performance

C# vs GDScript

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 and Array<T> in hot paths — Array<T> wraps the same engine array, so every element access still marshals a Variant. Use T[] or List<T> and convert at boundaries.
• StringName lookups are O(1) but StringName construction is not — cache them if created frequently.

9. Common Gotchas

⚠️ 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.WidthInPercent was renamed to WidthUnit (GH-112617; UPDATE_WIDTH_IN_PERCENT → UPDATE_WIDTH_UNIT in GDScript), 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