Custom UrlEncodedSerializer that utilizes DataContract and DataMember attributes

DataContractUrlEncodedSerializer.cs

public class DataContractUrlEncodedSerializer : ISerializer
{
    /// <summary>
    /// Serializes the specified object utilizing DataContract and DataMembers if present.
    /// </summary>
    /// <param name="obj">The object.</param>
    public string Serialize(object obj)
    {
        if (obj == null)
            return null;

        bool useDataMembers = TryGetDataMembers(obj, out IDictionary<string, string> dataMembers);

        var qp = new QueryParamCollection();
        foreach (var kv in obj.ToKeyValuePairs())
        {
            string key = useDataMembers && dataMembers.TryGetValue(kv.Key, out string dataKey) ? dataKey : kv.Key;
            qp.Merge(key, kv.Value, false, NullValueHandling.Ignore);
        }

        return qp.ToString(true);
    }

    private bool TryGetDataMembers(object obj, out IDictionary<string, string> dataMembers)
    {
        dataMembers = null;
        if (HasDataContract(obj))
        {
            dataMembers = obj.GetType().GetProperties()
                .Where(HasDataMember)
                .Select(ToDataMember)
                .ToDictionary(p => p.PropertyName, p => p.DataMemberName);

            return true;
        }

        return false;
    }

    private bool HasDataMember(PropertyInfo pi) =>
        Attribute.IsDefined(pi, typeof(DataMemberAttribute));

    private bool HasDataContract(object obj) =>
        obj.GetType().GetCustomAttributes(typeof(DataContractAttribute), true).Any();

    private static (string PropertyName, string DataMemberName) ToDataMember(PropertyInfo pi) =>
        (pi.Name, ((DataMemberAttribute)Attribute.GetCustomAttribute(pi, typeof(DataMemberAttribute))).Name);

    /// <summary>
    /// Deserializes the specified s.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="s">The s.</param>
    /// <exception cref="NotImplementedException">Deserializing to UrlEncoded not supported.</exception>
    public T Deserialize<T>(string s)
    {
        throw new NotImplementedException("Deserializing to UrlEncoded is not supported.");
    }

    /// <summary>
    /// Deserializes the specified stream.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="stream">The stream.</param>
    /// <exception cref="NotImplementedException">Deserializing to UrlEncoded not supported.</exception>
    public T Deserialize<T>(Stream stream)
    {
        throw new NotImplementedException("Deserializing to UrlEncoded is not supported.");
    }
}