https://learn.microsoft.com/en-us/dotnet/api/system.net.http.headers.httpcontentheaders.lastmodified?view=netframework-4.8.1&redirectedfrom=MSDN
HttpContentHeaders.LastModified Property (System.Net.Http.Headers) | Microsoft Learn
Gets or sets the value of the Last-Modified content header on an HTTP response.
property systemhttp headersmicrosoftlearn
https://learn.microsoft.com/zh-tw/dotnet/api/system.net.http.headers.httpcontentheaders?view=netframework-4.8.1&viewFallbackFrom=net-9.0
HttpContentHeaders Class (System.Net.Http.Headers) | Microsoft Learn
Represents the collection of Content Headers as defined in RFC 2616.
class systemhttp headersmicrosoftlearn