headers2.cs

[HttpGet]
[Route("products")]
public IHttpActionResult GetProducts([FromUri]string filter, [FromHeader]StandardGetHeaders headers)
{
    // validate headers (and any other bound fields), returning useful messages
    // upon failure
    if (!ModelState.IsValid) return BadRequest(ModelState);

    // run our query
    var results = RunGetProductsQuery(
        filter,
        headers.XPageNumber,
        headers.XPageSize);

    return Json(results);
}

// …

// this is a supporting “header model” class – to receive header values (if present)
// and define validation rules in a standardized way
public class StandardGetHeaders
{
    [Required("Wenk!")]
    public string XSecretPenguinHandshake { get; set; }

    [Range(1, int.MaxValue, "Page number must be greater than 0")]
    public int XPageNumber { get; set; }

    [Range(1, 100, "Page size must be between 1 and 100")]
    public int XPageSize { get; set; }
}