/// <summary>
/// Gets the single related CLR resource referenced by the "to-one" relationship.
/// </summary>
/// <typeparam name="TResource">Type of related CLR resource to get.</typeparam>
/// <param name="relationship">The "to-one" relationship object that defines the
/// single related CLR resource by json:api resource linkage.</param>
/// <returns>Returns the single related CLR resource referenced by the "to-one"
/// relationship if it exists, null otherwise.</returns>
/// <exception cref="DocumentReadException">Is thrown if the relationship object
/// passed is a "to-many" relationship instead of a "to-one" relationship.</exception>
public static TResource GetRelatedResource <TResource>(this IDocumentReader documentReader, Relationship relationship)
where TResource : class, IResource
{
Contract.Requires(documentReader != null);
Contract.Requires(relationship != null);
var clrRelatedResourceType = typeof(TResource);
var clrRelatedResource = (TResource)documentReader.GetRelatedResource(clrRelatedResourceType, relationship);
return(clrRelatedResource);
}