c# httpcontent "400 - Bad Request" if string contains newline character - json

Question

I am running into some kind of trouble communicating with a restful service from my .Net WPF application (.Net 4.5), in particular when sending a "PUT" request with some json data.
FYI: The restful service is running under Python Flask.
The method I use the following method to send request to the restful service:
HttpClient http = new HttpClient();
http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", encodedCredentials);
http.Timeout = TimeSpan.FromSeconds(1);
// Add an Accept header for JSON format.
http.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
HttpContent content = new StringContent(jDataString, Encoding.UTF8, "application/json");
When I submit usual string, all works just fine. But I am having trouble as soon as the string contains line breaks.
Using:
mytring.Replace("\r", "").Replace("\n", "")
works, my string is then accepted by the restful service.
Unfortunately, this is not acceptable, because I want to be able to retrieve line breaks.
I hence tried approaches like:
mytring.Replace("\n", "\\n").Replace("\r", "\\r")
or even with a inside-character to make sure I recognize the pattern:
mytring.Replace("\n", "\\+n").Replace("\r", "\\+r")
In both cases, my parsed string looks fine, but isn't accepted by the restful service.
Below two examples - the first version is accepted, not the second and third...
"XML_FIELD": "<IDs><Id Type=\"System.Int32\" Value=\"7\" /></IDs>"
"XML_FIELD": "<IDs>\r\n<Id Type=\"System.Int32\" Value=\"20\" />\r\n</IDs>"
"XML_FIELD": "<IDs>\+r\+n<Id Type=\"System.Int32\" Value=\"20\" />\+r\+n</IDs>"
Thanks in advance for the help!!
Regards!

Answer 1

Ok, got it...
The issue was coming from "\r\n" character which were coming directly from my DB...
Anyway, change to perform is for SERIALIZATION is
mySerializedString.Replace("\r\n", "\n")
.Replace("\n", "\\n")
.Replace("\r", "\\r")
.Replace("\'", "\\'")
.Replace("\"", "\\\"")
.Replace("\t", "\\t")
.Replace("\b", "\\b")
.Replace("\f", "\\f");
And to de-serialize do the inverse:
myDeSerializedString.Replace("\\n", "\n")
.Replace("\\r", "\r")
.Replace("\\'", "\'")
.Replace("\\\"", "\"")
.Replace("\\t", "\t")
.Replace("\\b", "\b")
.Replace("\\f", "\f");
NOTE: in the process, we loose "\r\n" characters (which are replaced by "\n").