Thomas Levesque • 7/23/2020

ASP.NET Core 3, IIS and empty HTTP headers

The article details a specific issue encountered when upgrading an ASP.NET Core 2.1 WOPI host to version 3.1, where empty HTTP headers (like X-WOPI-Lock) are silently removed by IIS in-process hosting, causing protocol test failures. It explains the HTTP specification validity of empty headers, traces the problem to a specific code change, and offers a practical workaround involving setting headers to a whitespace string.

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#Web Development #http headers #Azure