Writing code

Write C# code

ToCsharpString() writes any code object with the default settings. CSharpCodeGenerator writes it to a string, a TextWriter or an IndentedTextWriter, so you can write a file without building the whole text in memory:

var unit = new CompilationUnit();
unit.AddNamespace("MyNamespace").AddType(new ClassDeclaration("MyClass"));

var generator = new CSharpCodeGenerator();
string code = generator.Write(unit);

Assert.Equal("""
    namespace MyNamespace
    {
        class MyClass
        {
        }
    }

    """, code);

The generator writes \n line endings and indents with four spaces. To use other settings, create an IndentedTextWriter with the indentation and line ending you want, and pass it to Write.

Walk the tree

Every code object has a Parent, set when the object is added to a collection or assigned to a property. An object has only one parent: assigning an object that already belongs to another parent throws an ArgumentException, so create a new object for each place.

var unit = new CompilationUnit();
var ns = unit.AddNamespace("MyNamespace");
var cls = ns.AddType(new ClassDeclaration("MyClass"));

// Code objects form a tree
Assert.Same(ns, cls.Parent);
Assert.Same(unit, ns.Parent);

SelfOrAnscestorOfType<T>() and AnscestorOfType<T>() find the closest parent of a type, such as the type that declares a method.

Visitors

Visitor visits every object of a tree. Derive from it and override the Visit* method of the objects you are interested in, and call the base method to keep visiting their children:

private sealed class MethodNameCollector : Visitor
{
    public List<string?> Names { get; } = [];

    public override void VisitMethodDeclaration(MethodDeclaration methodDeclaration)
    {
        Names.Add(methodDeclaration.Name);
        base.VisitMethodDeclaration(methodDeclaration);
    }
}

var type = new ClassDeclaration("Sample");
type.AddMember(new MethodDeclaration("Write"));
type.AddMember(new PropertyDeclaration("Name", typeof(string)));
type.AddMember(new MethodDeclaration("Read"));

var collector = new MethodNameCollector();
collector.Visit(type);
Assert.Equal(["Write", "Read"], collector.Names);

// Sort the members: fields, properties, methods... then by name
DefaultFormatterVisitor.Instance.Visit(type);
Assert.Equal(["Name", "Read", "Write"], type.Members.Select(member => member.Name));

DefaultFormatterVisitor.Instance is a visitor that sorts the members of classes, structs and interfaces by kind, then by name. Run it before writing the code to get a stable order, whatever the order in which the members were added.

Attach data

Data is a dictionary on every code object, that the generator ignores. Use it to keep information from your model on the objects you create, for instance to find them again in a visitor.