声明期间可以使用匿名类型成员吗？

Question

Ok, so I'm trying to turn this:

sSelect = "SELECT CONVERT(VARCHAR, CommitDate, 101) AS XLabel, " +
    "SUM(CASE WHEN NOT CompletionDate IS NULL  THEN 1 ELSE 0 END) AS ClosedEvents, " +
    "COUNT(CommitDate) AS Total, " +
    "COUNT(CommitDate) - SUM(CASE WHEN NOT CompletionDate IS NULL THEN 1 ELSE 0 END) AS OpenEvents, " +
    "SUM(CASE WHEN CompletionDate IS NULL AND commitdate < Convert(varchar(12),getdate(),101) THEN 1    ELSE 0 END) AS BehindSchedule";

into a Linq query. So far I've got:

var vEventsEntriesEnum = dtEventsEntries.AsEnumerable();

var vOpenEntriesData = from r in vEventsEntriesEnum
select new
{
    XLabel = r["CommitDate"],
    ClosedEvents = vEventsEntriesEnum.Sum(closed => (closed["CompletionDate"] != null) ? 1 : 0),
    Total = vEventsEntriesEnum.Count(total => (total["CommitDate"] != null) ? true : false),
    OpenEvents = Total - ClosedEvents,
};

which is where I realized I might have a problem. Total and ClosedEvents do not exist in that context.

While I can just go ahead and repeat the queries for ClosedEvents and Total and cast then subtract them or whatever, I was hoping there'd be a better way.

If there are any other ways of doing what I'm doing with the rest of the code, feel free to let me know.

Any ideas?

Answer 1

You have to materialize it somewhere. In query syntax you can use the let clause :

var vOpenEntriesData = from r in vEventsEntriesEnum
    let ClosedEvents = vEventsEntriesEnum.Sum(closed => (closed["CompletionDate"] != null) ? 1 : 0)
    select new
    {
        XLabel = r["CommitDate"],
        ClosedEvents,
        Total = vEventsEntriesEnum.Count(total => (total["CommitDate"] != null) ? true : false),
        OpenEvents = Total - ClosedEvents,
    };

This is similar to a variable in a loop.