Question

我在LINQ中有以下声明：

var eventsWithTag = (from occurence in occurrences1
                     join eventTag in serviceContext.CreateQuery("adx_eventtag_event")
                         on occurence.Event.GetAttributeValue<Guid>("adx_eventid") equals eventTag.GetAttributeValue<Guid>("adx_eventid")
                     join tag in serviceContext.CreateQuery("adx_eventtag")
                         on eventTag.GetAttributeValue<Guid>("adx_eventtagid") equals tag.GetAttributeValue<Guid>("adx_eventtagid")
                     where tag.GetAttributeValue<string>("adx_name") == "scotland"
                     select occurence).OrderBy(x => x.Start);

这适用于此实例中“苏格兰”的固定字符串搜索。但是我需要替换它以反映当前页面主题。所以基本上我需要替换

== "scotland"

与

== getBranch()

其中getBranch将相关的分支名称作为字符串返回。

这会让我尝试

eventsWithTag = (from occurence in occurrences1
join eventTag in serviceContext.CreateQuery("adx_eventtag_event") on occurence.Event.GetAttributeValue<Guid>("adx_eventid") equals eventTag.GetAttributeValue<Guid>("adx_eventid")
join tag in serviceContext.CreateQuery("adx_eventtag") on eventTag.GetAttributeValue<Guid>("adx_eventtagid") equals tag.GetAttributeValue<Guid>("adx_eventtagid")
where tag.GetAttributeValue<string>("adx_name") == getBranch()
select occurence).OrderBy(x => x.Start);

但这不起作用，从我对LINQ的了解很少，因为你不能以这种方式使用变量。

所以我的问题是：如何使用上面的LINQ查询和分支的动态值。

请注意：我已经看过其他有关此事的帖子，但显然我没有LINQ知识可以将它们转移到我的特定需求。好吧！

Answer 1

您可以事先打电话：

var branch = getBranch();
eventsWithTag = 
    (from occurence in occurrences1
     join eventTag in serviceContext.CreateQuery("adx_eventtag_event") on occurence.Event.GetAttributeValue<Guid>("adx_eventid") equals eventTag.GetAttributeValue<Guid>("adx_eventid")
     join tag in serviceContext.CreateQuery("adx_eventtag") on eventTag.GetAttributeValue<Guid>("adx_eventtagid") equals tag.GetAttributeValue<Guid>("adx_eventtagid")
     where tag.GetAttributeValue<string>("adx_name") == branch 
     select occurence)
    .OrderBy(x => x.Start);

Answer 2

一切看起来都是正确的，所以我会仔细检查你的getBranch（）......

如果有效：

var branch = "scotland";
eventsWithTag = 
    (from occurence in occurrences1
     join eventTag in serviceContext.CreateQuery("adx_eventtag_event") on occurence.Event.GetAttributeValue<Guid>("adx_eventid") equals eventTag.GetAttributeValue<Guid>("adx_eventid")
     join tag in serviceContext.CreateQuery("adx_eventtag") on eventTag.GetAttributeValue<Guid>("adx_eventtagid") equals tag.GetAttributeValue<Guid>("adx_eventtagid")
     where tag.GetAttributeValue<string>("adx_name") == branch 
     select occurence)
    .OrderBy(x => x.Start);

然后p.s.w.g的答案应该有效，而你的问题在于getBranch返回的值与任何记录都不匹配......

在一个稍微不同的问题上，我有点困惑为什么你需要在你的equals语句中获得实际的属性，因为根据this，它应该像这样工作：

var branch = "scotland";
eventsWithTag = 
    (from occurence in occurrences1
     join eventTag in serviceContext.CreateQuery("adx_eventtag_event") on occurence.Event["adx_eventid"] equals eventTag["adx_eventid"]
     join tag in serviceContext.CreateQuery("adx_eventtag") on eventTag["adx_eventtagid"] equals tag["adx_eventtagid"]
     where tag["adx_name"] == branch 
     select occurence)
    .OrderBy(x => x.Start);

LINQ中的动态变量

2 个答案: