public static void Add(this IHeadersCollection headersCollection, string name, string value)
{
if (headersCollection == null)
{
throw new ArgumentNullException(nameof(headersCollection));
}
if (headersCollection.Contains(name))
{
throw new InvalidOperationException($"The name of {name} already exists in the header collection");
}
headersCollection.Add(new KeyValuePair <string, IEnumerable <string> >(name, new List <string> {
value
}));
}