HttpCachePolicy::SetETag Method
Sets the ETag HTTP header to the specified string.
Assembly: System.Web (in System.Web.dll)
Parameters
- etag
- Type: System::String
The text to use for the ETag header.
| Exception | Condition |
|---|---|
| ArgumentNullException | etag is nullptr. |
| InvalidOperationException | The ETag header has already been set. - or - The SetETagFromFileDependencies has already been called. |
The ETag header is a unique identifier for a specific version of a document. It is used by clients to validate client-cached content to avoid requesting it again. Once an ETag header is set, subsequent attempts to set it fail and an exception is thrown.
SetETag is introduced in the .NET Framework version 3.5. For more information, see .NET Framework Versions and Dependencies.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.