private ICollection <UserConfiguration> InternalFindUserConfigurations(Folder folder, string searchString, UserConfigurationSearchFlags searchFlags) { EnumValidator.ThrowIfInvalid <UserConfigurationSearchFlags>(searchFlags, "searchFlags"); if (searchString == null) { ExTraceGlobals.StorageTracer.TraceError <string>((long)this.GetHashCode(), "Folder::FindUserConfigurations. Argument {0} is Null.", "searchString"); throw new ArgumentNullException(ServerStrings.ExNullParameter("searchString", 1)); } return(UserConfiguration.Find(folder, searchString, searchFlags)); }