在c#中迭代列表时出现索引超出范围异常

我的控制器代码:

    public ActionResult Index(string priceMin, string priceMax)
    {
        lstEventType = HttpRuntime.Cache["EventType"] as List<string>;
        if (lstEventType == null || !lstEventType.Any())
        {
            lstEventType = new List<string>();
            lst = artistModel.fillDropDown();
            lstEventType = lst.Where(p => p.lookupType == "EventType").Select(q => q.lookupValue).ToList();
            HttpRuntime.Cache["EventType"] = lstEventType;
        }
        ViewData["EventType"] = lstEventType;
        artistList = artistModel.displayArtist();    
        if (!String.IsNullOrEmpty(priceMin))
        {
            aSession.priceMin = priceMin;
            ViewData["priceMin"] = priceMin;
            artistList = artistList.Where(p => (string.IsNullOrEmpty(p.strHiddenCost) ? 0 : Convert.ToInt32(p.strHiddenCost)) >= Convert.ToInt32(priceMin)).ToList();
        }
        if (!String.IsNullOrEmpty(priceMax))
        {
            aSession.priceMax = priceMax;
            ViewData["priceMax"] = priceMax;
            artistList = artistList.Where(p => (string.IsNullOrEmpty(p.strHiddenCost) ? 0 : Convert.ToInt32(p.strHiddenCost)) <= Convert.ToInt32(priceMax)).ToList();
        }         
        return View(artistList);
    }

如果这个artistList返回非值，那么我没有得到任何错误。但是如果artistList返回null，视图中下面的代码部分就会抛出异常。我无法弄清楚这个artistList是如何影响viewdata["EventType"]的。

下面是我的代码在视图

@{
   List<string> EventTypes = ViewData["EventType"] as List<string>;
        foreach (string eventType in EventTypes)
          {    
            <li><a> <span class="pull-right"></span>@eventType</a></li>
          }
   }

当通过这个循环迭代时，我得到了索引超出范围的异常。如果我的控制器返回一个非空列表到这个视图，那么它的工作很好。但是，如果控制器返回空列表来查看，则迭代失败。

@{
    List<string> EventTypeList= ViewData["EventType"] as List<string>;
    if (EventTypeList != null && EventTypeList.Count > 0){
        foreach (string eventType in EventTypeList)
        {
            <li><a> <span class="pull-right">@eventType</span></a></li>
        }
    }
}