contentLength property
int contentLengthThe content length of the request body.
If the size of the request body is not known in advance, this value is -1.
Source
int get contentLength;
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/1.24.3/dart-io/HttpRequest/contentLength.html