anchor.diff:                      Ok { Start = startOfRange; End = endOfRange }
   
       /// Helper method to parse and validate the If-Range HTTP header
  -    let matchesIfRange (request      : HttpRequest)
  +    let isIfRangeValid (request      : HttpRequest)
                          (eTag         : EntityTagHeaderValue option)
                          (lastModified : DateTimeOffset option) =
           let ifRange = request.GetTypedHeaders().IfRange
  
positive.code:                                  (lastModified          : DateTimeOffset option) =
          task {
              match this.ValidatePreConditions eTag lastModified with
              | ConditionFailed        -> return this.NotModifiedResponse()
              | NotModified            -> return this.PreConditionFailedResponse()
  
              // If all pre-conditions have been met (or didn't exist) then proceed with web request execution
              | IsMatch | NotSpecified ->
  
negative.code:                     | None         -> return! this.WriteStreamToBodyAsync stream None
                      | Some ranges  ->
                          // Check and validate If-Range HTTP header
                          match RangeHelper.isIfRangeValid this.Request eTag lastModified with
                          | false -> return! this.WriteStreamToBodyAsync stream None
                          | true  ->
                              match RangeHelper.validateRanges ranges stream.Length with
  