LINQ基本操作

public class Product
{
public string Name { get; set; }
public int CategoryID { get; set; }
}
public class Category
{
public string Name { get; set; }
public int ID { get; set; }
}

static List<Category> categories = new List<Category>()
{
new Category(){Name="Beverages", ID=001},
new Category(){Name="Condiments", ID=002},
new Category(){Name="Vegetables", ID=003},
new Category(){Name="Grains", ID=004},
new Category(){Name="Fruit", ID=005},
new Category(){Name="Other", ID=006}
};
static List<Product> products = new List<Product>()
{
new Product{Name="Cola",  CategoryID=001},
new Product{Name="Tea",  CategoryID=001},
new Product{Name="Mustard", CategoryID=002},
new Product{Name="Pickles", CategoryID=002},
new Product{Name="Carrots", CategoryID=003},
new Product{Name="Bok Choy", CategoryID=003},
new Product{Name="Peaches", CategoryID=005},
new Product{Name="Melons", CategoryID=007},
};

foreach (var c in orderByResult)
Console.WriteLine("ID={0},Name={1}", c.ID, c.Name); 

var orderByResult = from c in categories
orderby c.ID //默认为升序，也可以在后面加上ascending
                            select c;
// 方法
var orderByResult = categories.OrderBy(c=>c.ID);

var orderByResult = from c in categories
orderby c.ID descending
select c;
// 方法 
var orderByResult = categories.OrderByDescending(c=>c.ID);

var orderByResult = from c in categories
orderby c.ID,c.Name
select c;
//方法
var orderByResult = categories.OrderBy(c=>c.ID).ThenBy(c=>c.Name);

var orderByResult = from c in categories
orderby c.ID, c.Name descending
select c;
//方法
var orderByResult = categories.OrderByDescending(c=>c.ID).ThenByDescending(c=>c.Name);