/// <summary>
/// Initializes a new instance of the <see cref="DataSource"/> class.
/// </summary>
/// <param name="id">The source of data.</param>
/// <exception cref="ArgumentNullException">
/// <paramref name="id"/> is <b>null</b>.
/// </exception>
protected DataSource(DataSourceId id)
{
this.Id = id ?? throw new ArgumentNullException("id");
}