Telerik MVC图表无法渲染数据

Question

我正在创建一个由几个Telerik UI for ASP.NET MVC Charts组成的仪表板。第一张图应该是针对给定代理逐月绘制销售量。我的控制器类如下：

        static List<SalesAgentViewModel> SalesAgentData = new List<SalesAgentViewModel>(){
        new SalesAgentViewModel
        {
             SalesAgentID = 1,
             ChartData = new List<SalesAgentChartItem>()
             {
                 new SalesAgentChartItem
                 {
                     MonthName="January",
                     MerchantMCVolume=25000,
                     MerchantVisaVolume=500000
                 },

                 new SalesAgentChartItem
                 {
                     MonthName="February",
                     MerchantMCVolume = 225000,
                     MerchantVisaVolume = 725000
                 },

                 new SalesAgentChartItem
                 {
                     MonthName="March",
                     MerchantMCVolume = 75000,
                     MerchantVisaVolume = 150250
                 }
             }
        },

        new SalesAgentViewModel
        {
            SalesAgentID = 2,
            ChartData = new List<SalesAgentChartItem>()
            {
                new SalesAgentChartItem
                {
                    MonthName="January",
                    MerchantMCVolume = 98000,
                    MerchantVisaVolume = 75250
                },
                new SalesAgentChartItem
                {
                    MonthName = "February",
                    MerchantMCVolume = 87500,
                    MerchantVisaVolume = 68250
                },
                new SalesAgentChartItem
                {
                    MonthName = "March",
                    MerchantMCVolume = 68500,
                    MerchantVisaVolume = 78125
                }
            }
        }
    };

    [Authorize(Roles ="Admin,SalesAgent")]
    public ActionResult ReadSalesAgentData([DataSourceRequest]DataSourceRequest request)
    {
        return Json(SalesAgentData.ToDataSourceResult(request));
    }

    [Authorize(Roles ="Admin,SalesAgent")]
    public ActionResult ReadGraphData(int id)
    {
        return Json(SalesAgentData.First(v => v.SalesAgentID == id).ChartData);
    }

然后，我在视图中新建了一个图表，如下所示：

<div class="container" id="dashboard">
 @(Html.Kendo().Chart<SalesAgentChartItem>()
  .Name("SalesAgentVolume")
  .Title("Sales Agent Volume")
  .DataSource(dataSource => dataSource
    .Read(read => read.Action("ReadGraphData","SalesAgents"))
    )
 .Series(series=>
  {
     series.Line(s => s.MerchantMCVolume).CategoryField("Mastercard Volume");
     series.Line(s => s.MerchantVisaVolume).CategoryField("Visa Volume");
  })
 .CategoryAxis(axis=>axis
    .Categories(model=>model.MonthName))
  )

 </div>

当我运行应用程序时，会呈现图形，但会抛出一个HTTP 500：

System.ArgumentException: The parameters dictionary contains a null entry    
for parameter 'id' of non-nullable type 'System.Int32' for method 
'System.Web.Mvc.ActionResult ReadGraphData(Int32)' in 
'Web.Controllers.SalesAgentsController'. An optional parameter must be a 
reference type, a nullable type, or be declared as an optional parameter.
Parameter name: parameters

我的目的是显示SalesAgentID标识的给定代理的卷。我该如何做到这一点？