What does the X-SourceFiles header do?

Using a FileStreamResult in ASP.NET MVC 3, I get a response header like

X-SourceFiles =?UTF-8?B?RDpcUHJvamVjdFxqYWNvYlx0ZXN0?=

Does anyone know what this head开发者_如何学JAVAer means, and what its purpose is?

The header is understood by certain debugging modules in IIS / IIS Express. It contains the base64-encoded path to the source file on disk and is used to link a page's generated output back to that source file. It's only generated for localhost requests, so you don't need to worry about it being displayed to the world when you deploy the application to an actual server.