Runtime: StringContent doesn't have an option to remove charset

[hungquach]

API shape:
```c#
class StringContent {
public StringContent(string content, MediaTypeHeaderValue mediaType);
public StringContent(string content, Encoding encoding, MediaTypeHeaderValue mediaType);

// Existing constructors:
public StringContent(string content);
public StringContent(string content, Encoding encoding);
public StringContent(string content, Encoding encoding, string mediaType);

}

## Original proposal

I'm using `HttpClient `to send the request but it seems `StringContent ` doesn't have an option to remove `charset `and I have to do it manually

REST endpoint only support `{application/json}` not `{application/json; charset=utf-8}`

```c#
apiClient.BaseAddress = new Uri("http://endpoint:8888");
apiClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

var json = JsonConvert.SerializeObject(new Dictionary<string, string>
{
    {"username", username},
    {"password", password}
});
var content = new StringContent(json, Encoding.UTF8, "application/json");
content.Headers.Remove("Content-Type"); // "{application/json; charset=utf-8}"
content.Headers.Add("Content-Type", "application/json");
var loginResponse = await apiClient.PostAsync("api/login", content);

Environment: .NET Core 2.0, .NET Standard 2.0

[EDIT] Add C# syntax highlighting by @karelz

[davidsh]

These are the current public constructors of StringContent.

```c#
public StringContent(string content);
public StringContent(string content, Encoding encoding);
public StringContent(string content, Encoding encoding, string mediaType);

All of them have the behavior of adding a `charset` attribute to the 'Content-Type` header.  We can't change the current behavior of these APIs.

But we could possibly add a new constructor overload that takes a `MediaTypeHeaderValue` parameter.  That would enable someone to pass in a custom value that didn't include any `charset` attribute:

Proposal:

```c#
public StringContent(string content, MediaTypeHeaderValue mediaTypeHeaderValue);

[hungquach]

I've just found another way to remove charset from content-type

c# var content = new StringContent(json, Encoding.UTF8, "application/json"); content.Headers.ContentType.CharSet = string.Empty;

[Priya91]

The second way looks good! If we expose an API, i don't think the mediatypeheadervalue allows Encoding to be set, it there also needs to be

c# public StringContent(string content, MediaTypeHeaderValue mediaType); public StringContent(string content, Encoding encoding, MediaTypeHeaderValue mediaType);

It's not clear and intuitive to figure out how to get the charset to be unset, exposing APIs sounds good.

@davidsh What do you think?

[karelz]

Triage: We need a little bit of validation if it works and is sufficient. Then we can send it to API review.

[willowTank]

I've just found another way to remove charset from content-type

var content = new StringContent(json, Encoding.UTF8, "application/json");
content.Headers.ContentType.CharSet = string.Empty;

Thank you very much.

[scalablecory]

@ckadluba, It would help us push this through API review if you can fulfill @karelz's ask:

Triage: We need a little bit of validation if it works and is sufficient. Then we can send it to API review.

If you can post some examples of how using this API will compare with the workaround that @hungquach identified, that will help demonstrate any benefits. Next review is 1/28, so we have some time.

[ckadluba]

Thanks for clarifying @scalablecory. I'm not sure if the following is what you need for the API review, but i'll give it a try. If there is anything unclear or something else is required, please let me know.

Here is how to create a StringValue object with default encoding UTF-8 but without charset label on Content-type header using new ctor from the suggested API change.

var content = new StringContent(json, 
   new MediaTypeHeaderValue("application/json")
   {
      CharSet = string.Empty
   });

Compared to creating the same with the existing workaround.

var content = new StringContent(json, "application/json");
content.Headers.ContentType.CharSet = string.Empty;

The first variant has the benefit that content could be treated as immutable after beeing created. It would allow changing the StringContent class and all its child properties to be immutable and still be able to create a StringContent object that renders no charset label into the Content-type header.

With the second added ctor, also custom encodings (other than default UTF-8) could be used.

var content = new StringContent(json, Encoding.UTF7 
   new MediaTypeHeaderValue("application/json"));

But this can also be done with the existing ctor with the signature StringContent(string, Encoding, string).

var content = new StringContent(json, Encoding.UTF7, "application/json");

The charset is in both cases deducted from the passed Encoding object.

Actually these scenarios are not a yet a real benefit over the workaround. Making the full object graph immutable would probably mean significant changes in all involved classes. But the added constructors would at least remove one obstacle when going into that direction, while still allowing to customize charset and other properties.

[GrabYourPitchforks]

The related item https://github.com/dotnet/corefx/issues/7864 was discussed and approved in today's API review. Closing this item.