ETag 的语法？

Question

Redbot 报告我的网页包含无效标头：

ETag 标头的语法无效。

我的标题设置为：

ETag: 4ae413bd

为什么无效？

ETag 的语法是什么？

Answer 1

尝试ETag：“4ae413bd”。
ETag 的值必须遵循 ABNF 形式：

  entity-tag = [ weak ] opaque-tag
  weak       = "W/"
  opaque-tag = quoted-string

  quoted-string  = ( <"> *(qdtext | quoted-pair ) <"> )
  qdtext         = <any TEXT except <">>
  quoted-pair    = "\" CHAR
  CHAR           = <any US-ASCII character (octets 0 - 127)>
  TEXT           = <any OCTET except CTLs, but including LWS>
  OCTET          = <any 8-bit sequence of data>
  LWS            = [CRLF] 1*( SP | HT )
  CTL            = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
  CRLF           = CR LF
  CR             = <US-ASCII CR, carriage return (13)>
  LF             = <US-ASCII LF, linefeed (10)>
  SP             = <US-ASCII SP, space (32)>
  HT             = <US-ASCII HT, horizontal-tab (9)>

，这基本上是([wW]/)?"([^"]|\\")*" 在常规正则表达式中。

请注意，"\" 和 "/" 都是 etag 的有效值。

参考文献：section-14.19，第 3.11 节，部分-2.2。

Answer 2

正如阿诺提到的，请确保您引用了该值。

替换

new EntityTagHeaderValue("0");

为

new EntityTagHeaderValue("\"0\"");

Answer 3

“ETag 是一个不透明标识符，由网络服务器分配给在 URL 上找到的资源的特定版本”。这意味着它几乎可以是任何东西。

问题可能是语法，使用：

ETag: "4ae413bd"

Answer 4

如果您是因为下面的堆栈跟踪而到达这里，请确保在 Visual Studio 中取消选中导致此错误的“启用浏览器链接”选项：

Conversion> [13:31:10 ERR] Connection id "0HLJ153E20LDJ", Request id "0HLJ153E20LDJ:00000003": An unhandled exception was thrown by the application.
Conversion> System.ObjectDisposedException: The response has been aborted due to an unhandled application exception. ---> System.FormatException: Invalid ETag name
Conversion>    at Microsoft.Net.Http.Headers.EntityTagHeaderValue..ctor(StringSegment tag, Boolean isWeak)
Conversion>    at Microsoft.Net.Http.Headers.EntityTagHeaderValue..ctor(StringSegment tag)
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.BrowserLinkMiddleWareUtil.AddToETag(ResponseHeaders responseHeader, Int32 port)
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.BrowserLinkMiddleware.<>c__DisplayClass7_0.<ExecuteWithFilter>b__0()
Conversion>    at Microsoft.AspNetCore.Http.HttpResponse.<>c.<.cctor>b__30_0(Object callback)
Conversion>    at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.FireOnStartingMayAwait(Stack`1 onStarting)
Conversion>    --- End of inner exception stack trace ---
Conversion>    at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ThrowResponseAbortedException()
Conversion>    at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.InitializeResponseAsync(Int32 firstWriteByteCount)
Conversion>    at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.WriteAsync(ReadOnlyMemory`1 data, CancellationToken cancellationToken)
Conversion>    at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpResponseStream.WriteAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
Conversion>    at System.IO.Stream.WriteAsync(Byte[] buffer, Int32 offset, Int32 count)
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.ScriptInjectionFilterStream.<>c__DisplayClass37_0.<<CreateResponseHandler>b__0>d.MoveNext()
Conversion> --- End of stack trace from previous location where exception was thrown ---
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.SocketReader.ReadBytesIntoResponseHandler(Int64 totalBytesToRead, ResponseHandler handler, CancellationToken cancellationToken)
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.HttpSocketAdapter.ResponseReader.ReadBytesIntoResponse(Int64 bytesToRead)
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.HttpSocketAdapter.ResponseReader.ReadChunkedContent()
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.HttpSocketAdapter.ResponseReader.ReadResponse()
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.DelayConnectingHttpSocketAdapter.Microsoft.VisualStudio.Web.BrowserLink.IHttpSocketAdapter.WaitForResponseComplete()
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.ScriptInjectionFilterStream.WaitForFilterComplete()
Conversion>    at Microsoft.VisualStudio.Web.BrowserLink.BrowserLinkMiddleware.ExecuteWithFilter(IHttpSocketAdapter injectScriptSocket, String requestId, HttpContext httpContext)
Conversion>    at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
Conversion>    at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
Conversion>    at Microsoft.AspNetCore.Server.IISIntegration.IISMiddleware.Invoke(HttpContext httpContext)
Conversion>    at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ProcessRequests[TContext](IHttpApplication`1 application)