R# plugin class creation sample

gistfile1.cs

    private static class ReadOnlyIntefaceBuilderWorkflow
    {
      public static WorkflowResult Start([CanBeNull] CSharpGeneratorContext context, CSharpElementFactory factory)
      {
        if (context.ClassDeclaration == null) return WorkflowResult.Inapplicable;
        return CreateNewInterfaceDeclaration(context, factory);
      }

      private static WorkflowResult CreateNewInterfaceDeclaration(CSharpGeneratorContext context, CSharpElementFactory factory)
      {
        string interfaceName = "IReadOnly" + context.ClassDeclaration.DeclaredName;
        var itfDecl = (IInterfaceDeclaration)factory.CreateTypeMemberDeclaration("interface " + interfaceName + " {}");
        return AddInterfaceToContainingNamespace(context, itfDecl, factory);
      }

      private static WorkflowResult AddInterfaceToContainingNamespace(CSharpGeneratorContext context, IInterfaceDeclaration itfDecl, CSharpElementFactory factory)
      {
        var ns = context.ClassDeclaration.GetContainingNamespaceDeclaration();
        if (ns == null) return WorkflowResult.Inapplicable;
        else
        {
          var typeDecl = ns.AddTypeDeclarationBefore(itfDecl, context.ClassDeclaration);
          return PopulateInterfaceDeclaration(context, factory, (IInterfaceDeclaration)typeDecl);
        }
      }

      private static WorkflowResult PopulateInterfaceDeclaration(CSharpGeneratorContext context, CSharpElementFactory factory, IInterfaceDeclaration itfDecl)
      {
        var props = context.InputElements.OfType<GeneratorDeclaredElement<ITypeOwner>>().ToList();
        foreach (var prop in props)
        {
          var propDecl = (IClassMemberDeclaration)factory.CreateTypeMemberDeclaration("public $0 $1 { get; }", prop.DeclaredElement.Type, prop.DeclaredElement.ShortName);
          itfDecl.AddClassMemberDeclaration(propDecl);
        }
        return EnsureClassImplementsInterface(context, itfDecl);
      }

      private static WorkflowResult EnsureClassImplementsInterface(CSharpGeneratorContext context, IInterfaceDeclaration itfDecl)
      {
        var interfaceType = TypeFactory.CreateType(itfDecl.DeclaredElement);
        context.ClassDeclaration.AddSuperInterface(interfaceType, false);
        return WorkflowResult.Success;
      }
    }