语言集成查询

using System;
using System.Linq;

namespace DuckTyping
{
    internal class Program
    {
        private static void Main()
        {
            int[] array = { 1, 5, 2, 10, 7 };  
            // Select squares of all odd numbers in the array sorted in descending order
            var results = from x in array
                                     where x % 2 == 1
                                     orderby x descending
                                     select x * x;
            foreach (var result in results)
            {
                Console.WriteLine(result); 
            }
        }
    }
}

// the Northwind type is a subclass of DataContext created by SQLMetal
// Northwind.Orders is of type Table<Order>
// Northwind.Customers is of type Table<Customer>

Northwind db = new Northwind(connectionString);
 
// use 'var' keyword because there is no name for the resultant type of the projection
 
var q =  from o in db.Orders
         from c in db.Customers
         where o.Quality == "200" && (o.CustomerID == c.CustomerID)
         select new { o.DueDate, c.CompanyName, c.ItemID, c.ItemName };
 
// q is now an IEnumerable<T>, where T is the anonymous type generated by the compiler

foreach (var t in q)
{
    // t is strongly typed, even if we can't name the type at design time
 
    Console.WriteLine("DueDate Type = {0}", t.DueDate.GetType());
    Console.WriteLine("CompanyName (lowercased) = {0}", t.CompanyName.ToLower());
    Console.WriteLine("ItemID * 2 = {0}", t.ItemID * 2);
}