c# LINQ Query：分组后的平均值
假设我有一个包含多列的数据表。
我想对日期列进行分组，对于每个日期，我想计算出结果列的平均值。
我有以下代码，但未按预期工作：
var results = from res in dt.AsEnumerable()
group res by res.Field<string>("operation_time")
into grp
orderby grp.Key
select new
{
date = grp.Key,
sum = grp.Average(r => r.Field<double>("result"))
};
有人可以建议我如何做到这一点吗？
Say I have a datatable with a number of columns.
I want to group the date column and for each date, I want to work out the average value of the result column.
I have the following code which is not working as expected:
var results = from res in dt.AsEnumerable()
group res by res.Field<string>("operation_time")
into grp
orderby grp.Key
select new
{
date = grp.Key,
sum = grp.Average(r => r.Field<double>("result"))
};
Could somebody advise how I can do this?
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您按
operation_time字段作为字符串进行排序，这不太可能是您想要的。您应该使用各自的
Parse方法将其解析为int或DateTime。You're sorting by the
operation_timefield as a string, which is unlikely to be what you want.You should parse it into an
intorDateTimeusing their respectiveParsemethods.