Question

我无法正确获取我的linq查询。我一直在抵制使用foreach循环这样做，因为我正在努力更好地理解linq。

我在LinqPad中有以下数据。

void Main()
{
    var events = new[] {
        new {ID = 1, EventLevel = 1, PatientID = "1", CodeID = "2", Occurences = 0 },
        new {ID = 2, EventLevel = 2, PatientID = "1", CodeID = "2", Occurences = 0 },
        new {ID = 3, EventLevel = 1, PatientID = "2", CodeID = "1", Occurences = 0 },
        new {ID = 4, EventLevel = 3, PatientID = "2", CodeID = "2", Occurences = 0 },
        new {ID = 5, EventLevel = 1, PatientID = "3", CodeID = "3", Occurences = 0 },
        new {ID = 6, EventLevel = 3, PatientID = "1", CodeID = "4", Occurences = 0 }
    };

    var filter = new FilterCriterion();
    var searches = new List<FilterCriterion.Occurence>();
    searches.Add(new FilterCriterion.Occurence() { CodeID = "1", MinOccurences = 2, MaxOccurences = 3 });
    searches.Add(new FilterCriterion.Occurence() { CodeID = "2", MinOccurences = 2, MaxOccurences = 3 });

    filter.Searches = searches;

    var summary = from e in events
        let de = new
        {
            PatientID = e.PatientID,
            CodeID = e.CodeID
        }
        group e by de into t
        select new
        {
            PatientID = t.Key.PatientID,
                CodeID = t.Key.CodeID,
            Occurences = t.Count(d => t.Key.CodeID == d.CodeID)
        };

    var allCodes = filter.Searches.Select(i => i.CodeID);

    summary = summary.Where(e => allCodes.Contains(e.CodeID));

    // How do I find the original ID property from the "events" collection and how do I 
    // eliminate the instances where the Occurences is not between MinOccurences and MaxOccurences.

    foreach (var item in summary)
        Console.WriteLine(item);
}

public class FilterCriterion
{

   public IEnumerable<Occurence> Searches { get; set; }

   public class Occurence
   {
       public string CodeID { get; set; }
       public int? MinOccurences { get; set; }
       public int? MaxOccurences { get; set; }
   }

}

我遇到的问题是需要通过MinOccurences和MaxOccurences过滤器属性过滤结果，最后我想要ID为1,2,3和4的“事件”对象。

如果您能提供帮助，请提前致谢。

Answer 1

要在处理结束时访问event.ID，您需要使用第一个查询传递它。改变select：

// ...
group e by de into t
select new
{
    PatientID = t.Key.PatientID,
    CodeID = t.Key.CodeID,
    Occurences = t.Count(d => t.Key.CodeID == d.CodeID),
    // taking original items with us
    Items = t
};

完成此操作后，您的最终查询（包括事件过滤器）可能如下所示：

var result = summary
    // get all necessary data, including filter that matched given item
    .Select(Item => new
        {
            Item,
            Filter = searches.FirstOrDefault(f => f.CodeID == Item.CodeID)
        })
    // get rid of those without matching filter
    .Where(i => i.Filter != null)
    // this is your occurrences filtering
    .Where(i => i.Item.Occurences >= i.Filter.MinOccurences
        && i.Item.Occurences <= i.Filter.MaxOccurences)
    // and finally extract original events IDs
    .SelectMany(i => i.Item.Items)
    .Select(i => i.ID);

这会产生1，2。 <{1}}和3被排除在外，因为它们没有过去发生过滤。

Answer 2

我在linqpad中运行你的程序。

我的理解是你要使用filter.MinOccurences和filter.MaxOccurences过滤结果数据集的Occurences数。

您可以使用Where子句添加其他过滤器。

if (filter.MinOccurences.HasValue)
 summary = summary.Where (x=> x.Occurences >= filter.MinOccurences);

if (filter.MaxOccurences.HasValue)
 summary = summary.Where (x=> x.Occurences <= filter.MaxOccurences);

Linq查询按字段1分组，计算字段2并按联接集合的值之间的计数进行筛选

2 个答案: