Question

我试图通过查询字符串过滤结果，但不确定最佳方法，到目前为止我所拥有的是：

var topic = Request.QueryString["topic"];
var date = Request.QueryString["date"];
var keyword = Request.QueryString["keyword"];

if (!string.IsNullOrEmpty(topic) || !string.IsNullOrEmpty(date) || !string.IsNullOrEmpty(keyword))
{
    items = root.Children().Where(x => x.IsDocumentType("Event-Item") &&
        x.GetPropertyValue("eventTitle").ToString().Contains(topic) || 
        x.GetPropertyValue("eventDates").ToString().Contains(date) || 
        x.GetPropertyValue("eventSummary").ToString().Contains(keyword)).OrderByDescending(x => x.CreateDate).ToList();
}
else
{
    items = root.Children().Where(x => x.IsDocumentType("Event-Item")).OrderByDescending(x => x.CreateDate).ToList();
}

这看起来是否正确？这样做有更好（更正确）的方法吗？非常感谢任何帮助。

Answer 1

我会把它分解如下。你总是过滤“Event-Item”，所以从if / else中取出然后先做。然后检查空值并根据需要进行过滤。最后，因为你总是在排序，所以在一切之后都这样做。

    var topic = Request.QueryString["topic"];
    var date = Request.QueryString["date"];
    var keyword = Request.QueryString["keyword"];

    items = root
              .Children()
              .Where(x => x.IsDocumentType("Event-Item"));

    if (!string.IsNullOrEmpty(topic) || !string.IsNullOrEmpty(date) || !string.IsNullOrEmpty(keyword))
    {
        items = items.Where(x =>                    
            x.GetPropertyValue("eventTitle").ToString().Contains(topic) || 
            x.GetPropertyValue("eventDates").ToString().Contains(date) || 
            x.GetPropertyValue("eventSummary").ToString().Contains(keyword));
    }

    items = items.OrderByDescending(x => x.CreateDate);

Answer 2

每个学期的条件where怎么样？

string topic = Request.QueryString["topic"];
string date = Request.QueryString["date"];
string keyword = Request.QueryString["keyword"];

var filteredItems = root.Children()
                        .Where(x => x.IsDocumentType("Event-Item"));
if (!string.IsNullOrEmpty(topic))
    filteredItems = filteredItems.Where(x => x.GetPropertyValue("eventTitle")
                                              .ToString()
                                              .Contains(topic));
if (!string.IsNullOrEmpty(date))
    filteredItems = filteredItems.Where(x => x.GetPropertyValue("eventDates")
                                              .ToString()
                                              .Contains(date));
if (!string.IsNullOrEmpty(keyword))
    filteredItems = filteredItems.Where(x => x.GetPropertyValue("eventSummary")
                                              .ToString()
                                              .Contains(keyword));
items = filteredItems.OrderByDescending(x => x.CreateDate).ToList();

如何从C＃中可能的Querystrings过滤Lambda表达式

2 个答案: