test.cs

[HttpGet]
[Route("List")]
public IEnumerable<DocumentData> List()
{
  // file all file names from App_Data
  var files = Directory.GetFiles("App_Data");
  var data = new List<DocumentData>();
  foreach (var file in files)
  {
    data.Add(new DocumentData
    {
      Name = Path.GetFileName(file),
    });
  }
  return data;
}