如何在.Net/C#中将日期转换为HTTP格式的日期#

DateTime dateTime = DateTime.Now;
string httpDate = dateTime.ToString("R");

DateTime dateTime = DateTime.Now;
DateTime utcDateTime = dateTime.ToUniversalTime();
string httpDate = utcDateTime.ToString("R");

HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Date = DateTimeOffset.UtcNow;