Validation is automatically done on Save, but can be triggered early:

public static void Validation()
  {
      using (var context = new CompanyContext())
      {
          var manager = new Manager() { Name = string.Empty };
          context.Managers.Add(manager);

        var validationErrors = context.GetValidationErrors()
            .Where(vr => !vr.IsValid)
            .SelectMany(vr => vr.ValidationErrors);
 
        foreach (var error in validationErrors)
        {
            Console.WriteLine(error.ErrorMessage);
        }
 
        Console.ReadKey();
    }
}

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