HeaderNames now contains static readonly fields instead of const fields

[Tratcher]

HeaderNames now contains static readonly fields instead of const fields

The static Microsoft.Net.Http.Headers.HeaderNames class contains string fields representing various common header names (e.g. HeaderNames.Origin). Starting in ASP.NET Core 3.0 Preview 5, these will change from const fields to static readonly fields.

See dotnet/aspnetcore#9514 for discussion.

Version introduced

3.0

Old behavior

These fields used to be const

New behavior

These fields are now static readonly.

Reason for change

The change prevents the values from being embedded across assembly boundaries allowing for value corrections as needed. It also enables faster reference equality checks.

Recommended action

Recompile against 3.0. Source code that used these fields as an attribute argument, a case in a switch statement, or when defining another constant will no longer be able to do so. To work around this break, developers can switch to using self-defined header name constants or string literals.

Category

• ASP.NET Core

Affected APIs

All fields on Microsoft.Net.Http.Headers.HeaderNames

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Issue metadata

• Issue type: breaking-change