Custom headers in WebRequest NET Core 3.1

Question

I'm trying to perform a web request from the client (NET Core 3.1) to a server. But I'm getting an error when passing custom information in headers. Please, I would like to know how to pass the information in the header. Thanks.

My code:

var request = (HttpWebRequest)WebRequest.Create("https://localhost:44351/mycontroller");
var postData = "n=42&s=25";
var data = Encoding.ASCII.GetBytes(postData);
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = data.Length;
request.Headers["X‐test"] = "884436999";

The exception:

Answer 1

Let's take a little tour at the related source code. In System.txt there is a row:

net_WebHeaderInvalidHeaderChars=Specified value has invalid HTTP Header characters.

That means we should look for this net_WebHeaderInvalidHeaderChars key in the source code of WebHeaderCollection:

//
// CheckBadChars - throws on invalid chars to be not found in header name/value
//
internal static string CheckBadChars(string name, bool isHeaderValue) {

    ...

    if (isHeaderValue) {
        ...
    }
    else {
        // NAME check
        //First, check for absence of separators and spaces
        if (name.IndexOfAny(ValidationHelper.InvalidParamChars) != -1) {
            throw new ArgumentException(SR.GetString(SR.net_WebHeaderInvalidHeaderChars), "name");
        }
        
        ...
    }
    return name;
}

This means that the error is thrown if the provided name contains some invalid characters.

The InvalidParamChars are defined inside the Internal class like this:

internal static readonly char[]  InvalidParamChars =
    new char[]{
    '(',
    ')',
    '<',
    '>',
    '@',
    ',',
    ';',
    ':',
    '\\',
    '"',
    '\'',
    '/',
    '[',
    ']',
    '?',
    '=',
    '{',
    '}',
    ' ',
    '\t',
    '\r',
    '\n'};

So, all you have to do is to make sure that the request header name does not contain any of the not allowed characters.