Up to date

This page is up to date for Redot 4.3. If you still find outdated information, please create an issue.

C# language features

This page provides an overview of the commonly used features of both C# and Redot and how they are used together.

Type conversion and casting

C# is a statically typed language. Therefore, you can't do the following:

var mySprite = GetNode("MySprite");
mySprite.SetFrame(0);

The method GetNode() returns a Node instance. You must explicitly convert it to the desired derived type, Sprite2D in this case.

For this, you have various options in C#.

Casting and Type Checking

Throws InvalidCastException if the returned node cannot be cast to Sprite2D. You would use it instead of the as operator if you are pretty sure it won't fail.

Sprite2D mySprite = (Sprite2D)GetNode("MySprite");
mySprite.SetFrame(0);

Using the AS operator

The as operator returns null if the node cannot be cast to Sprite2D, and for that reason, it cannot be used with value types.

Sprite2D mySprite = GetNode("MySprite") as Sprite2D;
// Only call SetFrame() if mySprite is not null
mySprite?.SetFrame(0);

Using the generic methods

Generic methods are also provided to make this type conversion transparent.

GetNode<T>() casts the node before returning it. It will throw an InvalidCastException if the node cannot be cast to the desired type.

Sprite2D mySprite = GetNode<Sprite2D>("MySprite");
mySprite.SetFrame(0);

GetNodeOrNull<T>() uses the as operator and will return null if the node cannot be cast to the desired type.

Sprite2D mySprite = GetNodeOrNull<Sprite2D>("MySprite");
// Only call SetFrame() if mySprite is not null
mySprite?.SetFrame(0);

Type checking using the IS operator

To check if the node can be cast to Sprite2D, you can use the is operator. The is operator returns false if the node cannot be cast to Sprite2D, otherwise it returns true. Note that when the is operator is used against null the result is always going to be false.

if (GetNode("MySprite") is Sprite2D)
{
    // Yup, it's a Sprite2D!
}

if (null is Sprite2D)
{
    // This block can never happen.
}

You can also declare a new variable to conditionally store the result of the cast if the is operator returns true.

if (GetNode("MySprite") is Sprite2D mySprite)
{
    // The mySprite variable only exists inside this block, and it's never null.
    mySprite.SetFrame(0);
}

For more advanced type checking, you can look into Pattern Matching.

Preprocessor defines

Redot has a set of defines that allow you to change your C# code depending on the environment you are compiling to.

Examples

For example, you can change code based on the platform:

    public override void _Ready()
    {
#if (GODOT_32 || GODOT_MOBILE || GODOT_WEB)
        // Use simple objects when running on less powerful systems.
        SpawnSimpleObjects();
#else
        SpawnComplexObjects();
#endif
    }

Or you can detect which engine your code is in, useful for making cross-engine libraries:

    public void MyPlatformPrinter()
    {
#if GODOT
        GD.Print("This is Redot.");
#elif UNITY_5_3_OR_NEWER
        print("This is Unity.");
#else
        throw new NotSupportedException("Only Redot and Unity are supported.");
#endif
    }

Or you can write scripts that target multiple Redot versions and take advantage of features that are only available on some of those versions:

    public void UseCoolFeature()
    {
#if GODOT4_3_OR_GREATER || GODOT4_2_2_OR_GREATER
        // Use CoolFeature, that was added to Redot in 4.3 and cherry-picked into 4.2.2, here.
#else
        // Use a workaround for the absence of CoolFeature here.
#endif
    }

Full list of defines

  • GODOT is always defined for Redot projects.

  • TOOLS is defined when building with the Debug configuration (editor and editor player).

  • GODOT_REAL_T_IS_DOUBLE is defined when the GodotFloat64 property is set to true.

  • One of GODOT_64 or GODOT_32 is defined depending on if the architecture is 64-bit or 32-bit.

  • One of GODOT_LINUXBSD, GODOT_WINDOWS, GODOT_OSX, GODOT_ANDROID, GODOT_IOS, GODOT_WEB depending on the OS. These names may change in the future. These are created from the get_name() method of the OS singleton, but not every possible OS the method returns is an OS that Redot with .NET runs on.

  • GODOTX, GODOTX_Y, GODOTX_Y_Z, GODOTx_OR_GREATER, GODOTX_y_OR_GREATER, and GODOTX_Y_z_OR_GREATER, where X, Y, and Z are replaced by the current major, minor and patch version of Redot. x, y, and z are replaced by all values from 0 to the current version number for that component.

    Note

    These defines were first added in Redot 4.0.4 and 4.1. Version defines for prior versions do not exist, regardless of the current Redot version.

    For example: Redot 4.0.5 defines GODOT4, GODOT4_OR_GREATER, GODOT4_0, GODOT4_0_OR_GREATER, GODOT4_0_5, GODOT4_0_4_OR_GREATER, and GODOT4_0_5_OR_GREATER. Redot 4.3.2 defines GODOT4, GODOT4_OR_GREATER, GODOT4_3, GODOT4_0_OR_GREATER, GODOT4_1_OR_GREATER, GODOT4_2_OR_GREATER, GODOT4_3_OR_GREATER, GODOT4_3_2, GODOT4_3_0_OR_GREATER, GODOT4_3_1_OR_GREATER, and GODOT4_3_2_OR_GREATER.

When exporting, the following may also be defined depending on the export features:

  • One of GODOT_PC, GODOT_MOBILE, or GODOT_WEB depending on the platform type.

  • One of GODOT_WINDOWS, GODOT_LINUXBSD, GODOT_MACOS, GODOT_ANDROID, GODOT_IOS, or GODOT_WEB depending on the platform.

To see an example project, see the OS testing demo: https://github.com/redot-engine/redot-demo-projects/tree/master/misc/os_test