C # group statistics on the practical application of Linq and Lamda expressions,

C # group statistics on the practical application of Linq and Lamda expressions,

When creating statistical charts in a project, you need to perform grouping statistics on the queried list data. The first thought is to avoid frequent operations on the database.

Eg:

// Group the Cu elements in the list by year GroupBy // contains the year, average value, maximum value, total number // write Method 1: lamda expression write method (recommended) var listCu = list. groupBy (a =>. year ). select (g => (new {year = g. key, avg = g. average (m => m. cu), max = g. max (n => n. cu), count = g. count ()}); // write Method 2: the SQL-like language is written. The Compiler converts it to the lamda expression var listCu2 = from item in list group item by item. year into g select new {year = g. key, avg = g. average (m => m. cu), max = g. max (n => n. cu), count = g. count ()};