godot-csharp

Godot C# / .NET (4.x)

Write Godot game code in C#: node subclasses, the engine lifecycle, exports, signals as events, and GDScript interop. Targets Godot 4.3+ (.NET / C#); install the .NET SDK that matches your Godot version — .NET 6.0 for 4.3/4.4, .NET 8 for 4.5+.

When to use

• Use when scripting a Godot game in C# (.cs + .csproj), translating GDScript idioms to C#, exposing [Export] fields, or wiring [Signal] delegates and GetNode<T>.

When not to use: GDScript-specific syntax → godot-gdscript; engine concepts that are language-neutral (scenes, physics, animation) → the relevant godot-* skill. You need the Godot .NET build + the .NET SDK installed; the standard build can't run C#.

Core workflow

1. Use the Godot .NET editor build and install the matching .NET SDK (.NET 6.0 for Godot 4.3/4.4, .NET 8 for 4.5+). Creating the first C# script generates a .csproj/.sln. Build with the editor or dotnet build.
2. Every node script is a partial class extending a Godot type (the source generator relies on partial). The file/class name should match the node script.
3. Override lifecycle methods in PascalCase with double delta: _Ready(), _Process(double delta), _PhysicsProcess(double delta).
4. Expose tunables with [Export]; they show in the Inspector like GDScript @export.
5. Declare signals as [Signal] delegates named XxxEventHandler; emit with EmitSignal(SignalName.Xxx, ...) and subscribe with the generated C# event.
6. Get nodes with GetNode<T>("Path") (or %Unique), and call into GDScript with Call/Get/Set when needed.

Patterns

1. A node script: lifecycle, [Export], GetNode<T>

using Godot;

public partial class Player : CharacterBody2D
{
    [Export] public float Speed = 200.0f;          // editable in the Inspector
    [Export] public float JumpVelocity = -400.0f;

    private const float Gravity = 1200.0f;
    private AnimatedSprite2D _sprite;

    public override void _Ready()
    {
        _sprite = GetNode<AnimatedSprite2D>("AnimatedSprite2D");
    }

    public override void _PhysicsProcess(double delta)
    {
        Vector2 v = Velocity;                       // Velocity is a property here
        if (!IsOnFloor())
            v.Y += Gravity * (float)delta;          // delta is double; cast for float math
        if (Input.IsActionJustPressed("jump") && IsOnFloor())
            v.Y = JumpVelocity;

        float dir = Input.GetAxis("move_left", "move_right");
        v.X = dir != 0 ? dir * Speed : Mathf.MoveToward(v.X, 0, Speed);

        Velocity = v;
        MoveAndSlide();                             // no args, like GDScript 4.x
    }
}

2. Signals as C# events

using Godot;

public partial class Health : Node
{
    // Delegate name MUST end with "EventHandler"; generator creates the event + SignalName.
    [Signal] public delegate void HealthChangedEventHandler(int current, int max);

    private int _hp = 100;

    public void TakeDamage(int amount)
    {
        _hp = Mathf.Max(_hp - amount, 0);
        EmitSignal(SignalName.HealthChanged, _hp, 100);   // type-safe signal name
    }

    public override void _Ready()
    {
        HealthChanged += OnHealthChanged;            // subscribe like a normal C# event
    }

    private void OnHealthChanged(int current, int max) => GD.Print($"HP {current}/{max}");
}

3. Instancing a scene in C#

public partial class Spawner : Node2D
{
    // Load once; PackedScene is the C# equivalent of preload's result.
    private readonly PackedScene _bullet = GD.Load<PackedScene>("res://bullet.tscn");

    public void Shoot(Vector2 at)
    {
        var b = _bullet.Instantiate<Node2D>();       // typed instantiate
        b.GlobalPosition = at;
        AddChild(b);
    }
}

4. Interop with GDScript nodes

public override void _Ready()
{
    Node gd = GetNode("GDScriptNode");
    // Call a GDScript method and read/write its properties dynamically.
    gd.Call("take_damage", 10);
    int score = (int)gd.Get("score");
    gd.Set("score", score + 5);
    // Connect to a GDScript signal by name:
    gd.Connect("died", Callable.From(OnDied));
}

private void OnDied() => GD.Print("entity died");

Pitfalls

• Forgetting partial. Without partial, the Godot source generator can't extend the class and [Export]/[Signal] break with confusing build errors.
• Wrong method case/signature. C# overrides are _Ready, _Process(double), _PhysicsProcess(double) — PascalCase and double delta (GDScript uses snake_case and float). A mismatched name just won't be called.
• [Signal] delegate naming. It must end with EventHandler; the engine exposes the signal as the name without that suffix and generates SignalName.X and a C# event.
• GD.Print vs Console.WriteLine. Use GD.Print/GD.PrintErr to reach the Godot output panel; Console output may not appear.
• Value-type structs. Vector2, Color, Transform2D are structs — mutate a local copy (var v = Velocity; v.X = ...; Velocity = v;); editing Velocity.X directly won't compile/persist.
• Needs the .NET build + SDK. The non-.NET editor can't run C#; mismatched/missing .NET SDK causes build failures. Match the SDK to the Godot version (4.3/4.4 → .NET 6.0, 4.5+ → .NET 8; Android export on 4.5 needs .NET 9).
• QueueFree() vs Free() — same rules as GDScript; prefer QueueFree(). Disposed objects throw ObjectDisposedException if used after freeing.
• Export to some platforms differs for .NET (e.g. extra steps for web/mobile); check the .NET export notes for your target.

References

• For export attribute variants ([ExportGroup], ranges, typed arrays), async with await ToSignal(...), Godot.Collections vs System collections, custom Resources in C#, and project/build setup, read references/csharp-setup-and-interop.md.

Related skills

• godot-gdscript — the GDScript equivalents of these patterns.
• godot-signals-groups — signal/event architecture (language-neutral).
• godot-resources — data resources; the C# [Export] + Resource pattern.
• unity-csharp-scripting — C# in Unity, for developers coming from there.