Sorry, for the late response, but i was working on other topics the last weeks.
Today finally I found some time to spend again with this problem and it paid off. I finally found the solution for my problem. I looked at some examples on the net and instead of using:
//HttpWebRequestMgt.AddBodyAsText(JsonTextWriter.GetJSonAsText());
HttpWebRequestMgt.AddBodyAsAsciiText(JsonTextWriter.GetJSonAsText());
The difference between these two functions is that in the first row the body is send UTF-8 encoded and in the second it’s ASCII encoded.
Here the code from CU 1297 “Http Web Request Mgt.”:
AddBodyAsText(BodyText : Text)
// Assume UTF8
AddBodyAsTextWithEncoding(BodyText,Encoding.UTF8);
AddBodyAsAsciiText(BodyText : Text)
AddBodyAsTextWithEncoding(BodyText,Encoding.ASCII);
Thank you anyway @JayM for you’re suggestion, i will keep it in mind for the next time.