godot-csharp Checked

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. Godot 4.7 targets .NET 8; check current platform
  export notes because Android and other AOT targets can require newer SDK tooling.
- **`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.