httpClient ReadAsStringAsync encoding problem

I've created a Net Core 3.1 API that returns DOCX, DOC, RTF, PDF files, generated from a string. My problem is encoding. Using CURL from the command line is no problem, but using my api, although the code of files opened in notepad is seemingly similar, there are differences:

1. Valid file with CURL Notepad opens with ANSI encoding and mine with UTF-8

2. Normal letters are the same in both cases, only those with dashes and dots differ
   enter image description here

I tried different coding changes but nothing helped, please help.
To retrieve the content of the file, I use:

string response = response.Content.ReadAsStringAsync().Result;

I've tried a few encoding changes but so far it hasn't worked.

> My problem is encoding.

I think it's more than that. I think it's that you're trying to treat opaque binary data as a string to start with.

While RTF files are indeed text, all the other formats you mentioned (DOCX, DOC, PDF) are binary. Trying to treat arbitrary binary data as text will almost always lose information. You shouldn't be trying to store the data as a string - you should be reading it as a stream or a byte array. It's not clear what you're doing with the result afterwards, but if you're saving it to a file, I'd suggest opening a file stream, opening the response as a stream, and just using Stream.CopyTo to copy from the response to a file.

(As an aside, you should almost certainly be using await rather than the Task.Result property too.)

You may use something like this:

var client = new HttpClient();
var response = await client.GetByteArrayAsync(uri);
var responseString = Encoding.Unicode.GetString(response, 0, response.Length - 1);
return responseString;