使用LINQ统计指定日期下EventID唯一的记录数

Got it, let's tweak your existing LINQ query to count unique EventIDs for the specified date instead of just all matching records. Here's the adjusted code:

@Model.DateAndTimes
    .Where(f => f.DateAndTimeDateType.Value.DayOfYear == renderedDayWithTime.DayOfYear)
    .Select(f => f.EventID)
    .Distinct()
    .Count()

How this works: #

• The Where clause stays exactly as your original code, filtering records to only those matching the target date's day of year.
• Select(f => f.EventID) pulls out just the EventID values from the filtered records—we don't need the rest of the data for counting unique IDs.
• Distinct() removes duplicate EventID entries, so even if multiple records share the same EventID on the same date, it only keeps one instance.
• Finally, Count() gives you the total number of unique EventIDs for that date, which matches your example scenario (where 5 records with the same EventID would count as 1).

内容的提问来源于stack exchange，提问作者Mischa Morf