Handling of "invalid" HTTP header values results in values being incorrectly reordered #63833
Description
When we parse known multi-valued headers like Accept, we store any "invalid" values (i.e. values we couldn't parse) separately so that they will still be written to the wire and can still be enumerated via NonValidated. However, these invalid values are reordered relative to the rest of the values so that they always appear after valid values.
Repro code:
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, "http://microsoft.com");
request.Headers.TryAddWithoutValidation("Accept", "text/bar");
request.Headers.TryAddWithoutValidation("Accept", "invalid");
request.Headers.TryAddWithoutValidation("Accept", "text/baz");
Console.WriteLine("NonValidated before parsing (correct):");
PrintHeadersNonValidated(request);
// Force parsing
_ = request.Headers.Accept.Count;
Console.WriteLine("NonValidated after parsing (incorrect):");
PrintHeadersNonValidated(request);
static void PrintHeadersNonValidated(HttpRequestMessage request)
{
foreach (var header in request.Headers.NonValidated)
{
Console.WriteLine($" {header.Key}:");
foreach (var value in header.Value)
{
Console.WriteLine($" {value}");
}
}
Console.WriteLine();
} Output:
NonValidated before parsing (correct):
Accept:
text/bar
invalid
text/baz
NonValidated after parsing (incorrect):
Accept:
text/bar
text/baz
invalid
Note that this behavior is not limited to NonValidated -- it affects how the request headers are written to the wire when the request is sent.