I\'ve just declared a constant for the \"application/json\" content type in one of my classes.
public const string JsonContentType = \"application/json\";
In order to add an up-to-date answer: since dotnet core 2.1 MediaTypeNames.Application.Json
has been defined.
See https://github.com/dotnet/corefx/pull/26701 for the changeset.
While there are some MIME constants defined in MediaTypeNames (see here), there no constant for "application/json".
Putting additional content types in a shared const is probably best practice, better than defining them in string literals a million times throughout your code at least.
Plus it gives you the flexibility of using new/custom MIME types, which a specific .NET version might not have.