public RackRequest AddHeader(string headerName, string headerValue)
{
string prefix = RackEnvironmentVariables.GenericHeaderPrefix;
if (String.Equals(headerName, "Content-Length", StringComparison.CurrentCultureIgnoreCase) ||
String.Equals(headerName, "Content-Type", StringComparison.CurrentCultureIgnoreCase))
prefix = String.Empty;
headerName = headerName.ToUpper().Replace("-", "_");
return Add(prefix + headerName, headerValue);
}