public void NullPaths()
 {
     ApplianceCheck checker = new ApplianceExistsCheck(null, null,
                                                       ApplianceCheck.FileExtension.ovaovf);
     checker.Validate();
 }
        private bool CheckApplianceExists(out string error)
        {
            ApplianceCheck.FileExtension extension = m_comboBoxFormat.SelectedItem.ToString().Contains("xva")
                                                         ? ApplianceCheck.FileExtension.xva
                                                         : ApplianceCheck.FileExtension.ovaovf;

            ApplianceCheck check = new ApplianceExistsCheck(ApplianceDirectory, ApplianceFileName, extension);
            check.Validate();
            error = check.ErrorReason;
            return check.IsValid;
        }