HTTP response header, format for "Expires"

Question

I am setting this in C# with this line:

WebOperationContext.Current.OutgoingResponse.Headers.Add(HttpResponseHeader.Expires, DateTime.Now.AddSeconds(10).ToString());

Now I know the format is off on this as it expects the following: Tue, 06 Dec 2011 20:24:15 GMT

Is there a class in .NET implementing IFormatProvider I could leverage here? Or will I need to create my own?

Answer 1

I use DateTime.UtcNow.AddDays(30).ToString("R")

From MSDN:

The "R" or "r" standard format specifier represents a custom date and time format string that is defined by the DateTimeFormatInfo.RFC1123Pattern property. The pattern reflects a defined standard, and the property is read-only. Therefore, it is always the same, regardless of the culture used or the format provider supplied. The custom format string is "ddd, dd MMM yyyy HH':'mm':'ss 'GMT'". When this standard format specifier is used, the formatting or parsing operation always uses the invariant culture

Answer 2

You can use the Custom Date and Time Format Strings.

Tue, 06 Dec 2011 20:24:15 GMT

generate the above format like so:

DateTime.Now.AddDays(30).ToUniversalTime()
    .ToString("ddd, dd MMM yyyy HH:mm:ss 'GMT'");