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How to do aggregation without "group by" in Linq?

Everything I can find on linq for aggregation has a "group by" clause. How do I write this query in LINQ? I have a list of pairs of date values ​​and I want to take the average:

SELECT AVG(MySuff.Value) AS AvgValue FROM MyStuff
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6 answers


Answer to modified example (I believe):



var average = (from a in MyStuff
              select a.Value).Average();
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morning Alan:

int count = (from a in myContext.MyStuff
            select a).Count();

Assuming myContext is DataContext.



Note that this gives you immediate execution that you may not need.

Instead, you can store the query results in var:

var allResults = from a in myContext.MyStuff
                 select a;

//sometime later when needed
int count = allResults.Count(); // executes the SQL query now!
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There are many non-grouping grouping operators in LINQ. Alan's answer shows you the operator Count

, but MSDN lists others .

EDIT: Seeing your edit, it looks like you want Average .

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It should be noted that Alan LINQ code will give exactly AlanR SQL code, despite what you might assume otherwise.

However, caution should be exercised. If it was written as:

var q = from a in MyStuff select a;
int count = q.count();
foreach(MyStuff m in q) {...}

This will then generate two DB queries: the first as "select count (*) ..." and the second as "select * ...."

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Bit sorter

pairs.Average(a=>a.Value)

If there is no join, group or let, Query Expressions (from ...) is not worth it in my opinion.

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Thanks everyone for the help. Here's what I figured to work.

(from s in series select s).Average( a => a.Value )

Regards, Alan ... R

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