Angular Schematics - Could not find (undefined) at Object.getWorkspace

Question

i am trying to create a simple Schematics that read all template-files in my "./files/xxx" and copy the parsed ones into my angular app.

I am struggling with the following error:

Error: Could not find (undefined) at Object.getWorkspace (C:\MyProg\Client.Core\node_modules@schematics\angular\utility\config.js:22:15)

export function page(_options: PageSchema): Rule {
  return (tree: Tree, _context: SchematicContext) => {
    setupOptions(tree, _options);
    [...]
    return rule(tree, _context);
  };
}

export function setupOptions(host: Tree, options: any): Tree {
  const workspace = getWorkspace(host);
  if (!options.project) {
    options.project = Object.keys(workspace.projects)[0];
  }
  const project = workspace.projects[options.project];

  options.path = join(normalize(project.root), 'src');
  return host;
}

getWorkspace() is my problem.

Do you have any idea?

Ty in advance.