SPFile.ETag property

Gets an ETag that identifies a version of the file.

Namespace:  Microsoft.SharePoint
Assembly:  Microsoft.SharePoint (in Microsoft.SharePoint.dll)

public string ETag { get; }

Property value

Type: System.String
A string that contains the current ETag for the file.

ETags are hash stamps used to identify different versions of a file. Changes made to a file result in a new ETag being generated.