LINQ:从内部列表分组的列表中获取总和

将每个事务计划为{ Amount, Title }对象序列.然后按标记对这些对象进行分组,并计算每个组的金额总和:

account.Transactions
       .SelectMany(t => t.Tags.Select(tag => new { t.Amount, tag.Title }))
       .GroupBy(tagAmount => tagAmount.Title)
       .Select(g => new {
          TagName = g.Key,
          Sum = g.Sum(tagAmount => tagAmount.Amount)
       });

注意:此解决方案假定您在事务中没有重复的标记.否则你应该Distinct()在投射标签集合后添加调用.

与查询语法相同:

var query = from t in account.Transactions
            from tag in t.Tags
            select new { t.Amount, tag.Title } into tagAmount
            group tagAmount by tagAmount.Title into g
            select new
            {
                TagName = g.Key,
                Sum = g.Sum(tagAmount => tagAmount.Amount)
            };