Grouped Average : Average « LINQ « C# / CSharp Tutorial

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C# / CSharp Tutorial » LINQ » Average 
22.19.4.Grouped Average
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class MainClass {
    public static void Main() {

        List<Product> products = GetProductList();

        var categories =
           from p in products
           group p by p.Category into g
           select new Category = g.Key, AveragePrice = g.Average(p => p.UnitPrice) };

        Console.Write(categories);
    }
    static List<Product> GetProductList() {
        List<Product> empTree = new List<Product>();
        empTree.Add(new Product ProductName = "A", Category = "O", UnitPrice = 12, UnitsInStock = 5, Total = 36, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "B", Category = "O", UnitPrice = 2, UnitsInStock = 4, Total = 35, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "C", Category = "O", UnitPrice = 112, UnitsInStock = 3, Total = 34, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "D", Category = "O", UnitPrice = 112, UnitsInStock = 0, Total = 33, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "E", Category = "O", UnitPrice = 1112, UnitsInStock = 2, Total = 32, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "F", Category = "O", UnitPrice = 11112, UnitsInStock = 0, Total = 31, OrderDate = new DateTime(200511), Id = });
        return empTree;
    }
    static List<Customer> GetCustomerList() {
        List<Product> empTree = new List<Product>();
        empTree.Add(new Product ProductName = "A", Category = "O", UnitPrice = 12, UnitsInStock = 5, Total = 36, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "B", Category = "O", UnitPrice = 2, UnitsInStock = 4, Total = 35, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "C", Category = "O", UnitPrice = 112, UnitsInStock = 3, Total = 34, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "D", Category = "O", UnitPrice = 112, UnitsInStock = 0, Total = 33, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "E", Category = "O", UnitPrice = 1112, UnitsInStock = 2, Total = 32, OrderDate = new DateTime(200511), Id = });
        empTree.Add(new Product ProductName = "F", Category = "O", UnitPrice = 11112, UnitsInStock = 0, Total = 31, OrderDate = new DateTime(200511), Id = });

        List<Customer> l = new List<Customer>();
        l.Add(new Customer CompanyName = "A", Region = "R1", UnitsInStock = 1, Orders = empTree, CustomerId = });
        l.Add(new Customer CompanyName = "B", Region = "R2", UnitsInStock = 2, Orders = empTree, CustomerId = });
        l.Add(new Customer CompanyName = "C", Region = "R3", UnitsInStock = 3, Orders = empTree, CustomerId = });
        l.Add(new Customer CompanyName = "D", Region = "R4", UnitsInStock = 4, Orders = empTree, CustomerId = });
        l.Add(new Customer CompanyName = "E", Region = "R5", UnitsInStock = 5, Orders = empTree, CustomerId = });
        return l;
    }

}
class Customer : IComparable<Customer> {
    public string CompanyName get; set; }
    public string Region get; set; }
    public List<Product> Orders get; set; }
    public int UnitsInStock get; set; }
    public int CustomerId get; set; }

    public override string ToString() {
        return String.Format("Id: {0}, Name: {1}, Region: {3}"this.CustomerId, this.CompanyName, this.Region);
    }
    int IComparable<Customer>.CompareTo(Customer other) {
        if (other == null)
            return 1;

        if (this.CustomerId > other.CustomerId)
            return 1;

        if (this.CustomerId < other.CustomerId)
            return -1;

        return 0;
    }
}
class Product : IComparable<Product> {
    public string ProductName get; set; }
    public string Category get; set; }
    public int UnitPrice get; set; }
    public int UnitsInStock get; set; }
    public int Total get; set; }
    public DateTime OrderDate get; set; }
    public int Id get; set; }

    public override string ToString() {
        return String.Format("Id: {0}, Name: {1} , Category: {3}"this.Id, this.ProductName, this.Category);
    }
    int IComparable<Product>.CompareTo(Product other) {
        if (other == null)
            return 1;
        if (this.Id > other.Id)
            return 1;

        if (this.Id < other.Id)
            return -1;

        return 0;
    }
}
22.19.Average
22.19.1.Using Average to get the average of all values of an integer array.
22.19.2.Average with int array
22.19.3.Using Average to get the average length of the words in the string array.
22.19.4.Grouped Average
22.19.5.Using Average method to calculate the average value from a query
22.19.6.Numeric Aggregates: Average
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