Http post works in Postman but not in C# with HttpClient

Question

If I made a Http (Https) post through Postman everything works fine. But if I tried the same post with the HttpClient in .NET core it won't work it seems like the Authorization failed or something like that because the response.StatusCode is OK but if I read the content string I get a HTML page with 404 and its asking me if I like to login.

Of course I already checked the obvious things like the address and I tried different tokens (they always worked in postman). I also tried different versions of adding the Bearer token:

client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);

This is the code at the moment:

client.BaseAddress = new Uri("www.baseaddress.de");
client.DefaultRequestHeaders.Add("Authorization", "Bearer " + token);
var content = new StringContent(JsonConvert.SerializeObject(new { id = object.Id }), Encoding.UTF8, "application/json");
HttpResponseMessage response = await client.PostAsync($"/address", content);

Postman Headers:

The body:

I also tried it with insomnia and it works perfectly there too. Maybe postman do something in its header which I don't know? What are the common differences between postman an HttpClient? Does anyone have any other suggestion about what I could do or try to find the mistake?

Edit:

Fixed it by adding the / behind the base address and deleting it in front of the call:

client.BaseAddress = new Uri("www.baseaddress.de/");
HttpResponseMessage response = await client.PostAsync($"address", content);

Maybe anyone knows why the / is needed at the end of the base address, why can't I put it before the API call?

Answer 1

Instead of new { id = object.Id }.ToString() you need to do

JsonConvert.SerializeObject(new { id = object.Id })

Code like new { id = 77 }.ToString() produces "{ id = 77 }", not "{ id: "77" }"