Can Not Add Header To HttpClient

[hamiddd1980]

Library/API/IoT binding

nanoFramework.System.Net.Http

Visual Studio version

Microsoft Visual Studio Enterprise 2022 (64-bit) - Preview Version 17.14.0 Preview 2.0

.NET nanoFramework extension version

2022.12.136

Target name(s)

ESP32-S3

Firmware version

No response

Device capabilities

Target capabilities:
Has nanoBooter: NO
IFU capable: NO
Has proprietary bootloader: YES

Description

It is not possible to add Http headers (like User-Agent, Accept) to HttpClient by DefaultRequestHeaders or HttpRequestMessage . Trying to add standard Headers, produces the following exception:
Cannot update restricted header User-Agent.
Cannot update restricted header Accept.
Inspecting the online source code reveals that the problem arises from WebHeaderCollection class in ThrowOnRestrictedHeader method:
the class has a property named HInfo with type of HeaderInfoTable . HeaderInfoTable has a table with predefined Http Headers (Like User-Agent) .
User can not add a Http Header if that header exists in the HeaderInfoTable.
So, how can I add (or change) standard Http Header to httpClient (Like User-Agent,Accept)?

How to reproduce

1.Create a Static HttpClient
httpClient = new HttpClient();
2.Try to Add Headers To DefaultRequestHeaders

httpClient.DefaultRequestHeaders.Add("Accept", "application/json");
httpClient.DefaultRequestHeaders.Add("Accept-Language", "en-US,en;q=0.5");
 httpClient.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:136.0) Gecko/20100101 Firefox/136.0");

Expected behaviour

It should be possible to Add or Change Standard Http Headers to HttpClient

Screenshots

No response

Sample project or code

No response

Aditional information

No response

[Ellerbach]

As far as I remember, it's the same behavior on real .NET .Just try to add a header normally, it should just override the default one.

[hamiddd1980]

I'm sure it is possible to add Headers(standard or user defined) to HttpClient in .net Core.Indeed, many servers doesn't accept Http request in case the headers are empty.

[hamiddd1980]

Hi, is there any one here to help me?
Thanks in advance for your helps with this issue.

[hamiddd1980]

I think the following line from HttpHeaders class should be corrected (change boolean value from true to false):

public abstract class HttpHeaders
    {
       internal WebHeaderCollection _headerStore = new WebHeaderCollection(true); //we should change true param to false
       //the first parameter is m_IsHttpWebHeaderObject and according to comments for this property in WebHeaderCollection class, it should be TRUE if the object is created for internal use
       

        /// <summary>
        /// true if this object is created for internal use, in this case
        /// we turn on checking when adding special headers.
        /// </summary>
        private bool m_IsHttpWebHeaderObject = false;

[josesimoes]

@hamiddd1980 if you do that change can you add/modify the HTTP headers collection as you intend?

[hamiddd1980]

@josesimoes , I tested the above method and regarding the results below it seems this modification can solve the problem .

1-before modification :
1-1)if you try to add headers to Httpclient, you'll face the Exception :

1-2)and if you don't add headers , you don't have headers on server side:

2-after code modification :
2-1)you can include headers in Httpclient without problem:

2-2)on the server side,you receive these headers :

I'm not familiar with Github, so it would be grateful if you could apply this Modification .
Thank you.

[josesimoes]

Hi @hamiddd1980!
Thank you for the detailed investigation. Adding this to the work queue.

It's quite easy to do this: you can edit the file right on github and it will offer to open a pull request for you. No need to install anything, not clone locally.