方法上的Webapi参数为空

我试图以JSON格式将数据对象(WorkOrders)列表发送回我的Webapi控制器，这工作得非常好，除了数据对象参数(savemodel)在击中Webapi控制器时为空的轻微缺陷。这是JS的一个片段(slots是模拟数据)

var slots = [];    
            slots.push({ 'WorkOrder': 'XX21', 'OrderDate': '2015-10-11 00:00:00', 'Slot': '1', 'SageRef': 'HS11' });
            slots.push({ 'WorkOrder': 'XX22', 'OrderDate': '2015-10-12 00:00:00', 'Slot': '2', 'SageRef': 'HS12' })
            slots.push({ 'WorkOrder': 'XX23', 'OrderDate': '2015-10-13 00:00:00', 'Slot': '3', 'SageRef': 'HS13' });
            console.log(JSON.stringify({ 'savemodel': slots }))
            $.ajax({
                type: "POST",
                url: 'http://localhost:55821/api/schedule',
                data: JSON.stringify({ 'savemodel': slots }),
                contentType: 'application/json; charset=utf-8'                
            }).success(function (data) {
                $scope.$apply(function () {
                    if (data.SaveMessage.length > 0) {
                      // do something
                    }
                    else {
                      // do something else
                    }
                });
            });

模型:

    public class WorkOrderModel
{
    public string WorkOrder { get; set; }
    public string OrderDate { get; set; }
    public string SlotNumber { get; set; }
    public string SageRef { get; set; }
}

回发方法:

 [HttpPost]
        public IHttpActionResult UpdateWorkOrder([FromBody]List<WorkOrderModel> savemodel)
        {
            StringBuilder saveMessage = new StringBuilder();
            foreach (WorkOrderModel model in savemodel)
            {
                   // save the WO model object  here                
            }
            if (saveMessage.Length > 0)
            {
                return Ok(new { SaveMessage = "There were issues: " + saveMessage.ToString() });
            }
            else
            {
                return Ok(new { SaveMessage = "" });
            }
        }

发布JSONWebApi控制器中的空参数这是驱使我发疯，所以任何帮助将在这个阶段非常感激!

问候,itsdanny