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]);
}