Adding nullable type functionality for HttpRequest Context Type

[KellenCarl]

…icAPI.Unshipped.txt to reflect change to nullable type.

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PR Title
Adding nullability annotation on HttpRequest.ContentType

PR Description
Added "?" to make type string nullable for ContentType. Updated PublicAPI.Unshipped.txt to reflect change. I know there is at least one implementation error, but wanted to let code owners make decisions, provide feedback.

Addresses #32097

[dnfadmin]

All CLA requirements met.

[Tratcher]

The build shows two usages of this property that also need updating, DefaultHttpRequest and HttpLoggingMiddleware.

[BrennanConroy]

Looks like a couple places need to react to the nullability addition:
src/Middleware/HttpLogging/src/HttpLoggingMiddleware.cs#L118
src/Hosting/Hosting/src/Internal/HostingRequestStartingLog.cs#L50

[Tratcher]

Good, this fix found a bug in the logging middleware (@jkotalik). MediaTypeHelpers.TryGetEncodingForMediaType should allow string? and this should be changed to TryParse:

aspnetcore/src/Middleware/HttpLogging/src/MediaTypeHelpers.cs

Line 31 in 1453c5b

var mediaType = new MediaTypeHeaderValue(contentType);

[KellenCarl]

I am currently unable to figure out how to apply the TryParse. I see the MediaTypeHeaderValue has a method for it, but can't quite get it to work. I'll go ahead with the other fixes.

[KellenCarl]

I think this is what you were referring to:
31. MediaTypeHeaderValue.TryParse(contentType, out var mediaType);

When I added that, I received a build error that line 33 would be exposed to the possibility of a null value. And I didn't want to interfere with that logic or implementation.

33.        if (mediaType.Charset.HasValue)
    

[KellenCarl]

This implementation might work, but I am not sure this is what you are going for, or what you want to do with the null value:

if (!MediaTypeHeaderValue.TryParse(contentType, out var mediaType))
{
return false;
}

[Tratcher]

This implementation might work, but I am not sure this is what you are going for, or what you want to do with the null value:

if (!MediaTypeHeaderValue.TryParse(contentType, out var mediaType))
{
return false;
}

That's what I had in mind. It avoids throwing for null, empty, or bad contentTypes.

[ghost]

Hello @Tratcher!

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[Tratcher]

Thanks @KellenCarl!

Announcement: aspnet/Announcements#444 (comment)

[KellenCarl]

Thank you @Tratcher! I appreciate all the help and feedback!

[ghost]

Hi @KellenCarl. It looks like you just commented on a closed PR. The team will most probably miss it. If you'd like to bring something important up to their attention, consider filing a new issue and add enough details to build context.