public static string GetValue(this HttpRequestHeaders headers, string name) { var values = headers.FindValues(name).ToArray(); if (values.Length == 0) { throw new RequestHeaderException($"Cannot find request header '{name}'."); } if (values.Length > 1) { throw new RequestHeaderException($"Found request header '{name}' with values '{string.Join(",", values)}' but only one '{name}' value is allowed."); } return(values[0]); }