转:LinQ操作汇总（From CSharpSamples）

LinQ操作汇总（From CSharpSamples）

基本方法可以查看这里http://weblogs.asp.net/scottgu/archive/2007/07/16/linq-to-sql-part-5-binding-ui-using-the-asp-linqdatasource-control.aspx
最近学习LINQ资料不是很多，从CSHARPSAMPLE写一比较有用的例子方便大家学习。
1.INSERT/UPDATE/DELETE

insert Simple
public void LinqToSqlInsert01() {
    var q =
        from c in db.Customers
        where c.Region == "WA"
        select c;

    Console.WriteLine("*** BEFORE ***");
    ObjectDumper.Write(q);


    Console.WriteLine();
    Console.WriteLine("*** INSERT ***");
    var newCustomer = new Customer { CustomerID = "MCSFT",
                                     CompanyName = "Microsoft",
                                     ContactName = "John Doe",
                                     ContactTitle = "Sales Manager",
                                     Address = "1 Microsoft Way",
                                     City = "Redmond",
                                     Region = "WA",
                                     PostalCode = "98052",
                                     Country = "USA",
                                     Phone = "(425) 555-1234",
                                     Fax = null
                                   };
    db.Customers.InsertOnSubmit(newCustomer);
    db.SubmitChanges();


    Console.WriteLine();
    Console.WriteLine("*** AFTER ***");
    ObjectDumper.Write(q);



    Cleanup64();  // Restore previous database state
}

insert one to Many
public void LinqToSqlInsert02() {

    Northwind db2 = new Northwind(connString);

    DataLoadOptions ds = new DataLoadOptions();

    ds.LoadWith<nwind.Category>(p => p.Products);
    db2.LoadOptions = ds;

    var q = (
        from c in db2.Categories
        where c.CategoryName == "Widgets"
        select c);


    Console.WriteLine("*** BEFORE ***");
    ObjectDumper.Write(q, 1);


    Console.WriteLine();
    Console.WriteLine("*** INSERT ***");
    var newCategory = new Category { CategoryName = "Widgets",
                                     Description = "Widgets are the customer-facing analogues " +
                                                   "to sprockets and cogs."
                                   };
    var newProduct = new Product { ProductName = "Blue Widget",
                                   UnitPrice = 34.56M,
                                   Category = newCategory
                                 };
    db2.Categories.InsertOnSubmit(newCategory);
    db2.SubmitChanges();


    Console.WriteLine();
    Console.WriteLine("*** AFTER ***");
    ObjectDumper.Write(q, 1);

    Cleanup65();  // Restore previous database state
}

public void LinqToSqlInsert03() {

    Northwind db2 = new Northwind(connString);

    DataLoadOptions ds = new DataLoadOptions();
    ds.LoadWith<nwind.Employee>(p => p.EmployeeTerritories);
    ds.LoadWith<nwind.EmployeeTerritory>(p => p.Territory);

    db2.LoadOptions = ds;
    var q = (
        from e in db.Employees
        where e.FirstName == "Nancy"
        select e);



    Console.WriteLine("*** BEFORE ***");
    ObjectDumper.Write(q, 1);


    Console.WriteLine();
    Console.WriteLine("*** INSERT ***");
    var newEmployee = new Employee { FirstName = "Kira",
                                     LastName = "Smith"
                                   };
    var newTerritory = new Territory { TerritoryID = "12345",
                                       TerritoryDescription = "Anytown",
                                       Region = db.Regions.First()
                                     };
    var newEmployeeTerritory = new EmployeeTerritory { Employee = newEmployee,
                                                       Territory = newTerritory
                                                     };
    db.Employees.InsertOnSubmit(newEmployee);
    db.Territories.InsertOnSubmit(newTerritory);
    db.EmployeeTerritories.InsertOnSubmit(newEmployeeTerritory);
    db.SubmitChanges();


    Console.WriteLine();
    Console.WriteLine("*** AFTER ***");
    ObjectDumper.Write(q, 2);



    Cleanup66();  // Restore previous database state
}

update simple
public void LinqToSqlInsert04() {
    var q =
        from c in db.Customers
        where c.CustomerID == "ALFKI"
        select c;

    Console.WriteLine("*** BEFORE ***");
    ObjectDumper.Write(q);


    Console.WriteLine();
    Console.WriteLine("*** UPDATE ***");
    Customer cust = db.Customers.First(c => c.CustomerID == "ALFKI");
    cust.ContactTitle = "Vice President";
    db.SubmitChanges();


    Console.WriteLine();
    Console.WriteLine("*** AFTER ***");
    ObjectDumper.Write(q);

    Cleanup67();  // Restore previous database state
}

update mutiple
public void LinqToSqlInsert05() {
    var q = from p in db.Products
            where p.CategoryID == 1
            select p;

    Console.WriteLine("*** BEFORE ***");
    ObjectDumper.Write(q);


    Console.WriteLine();
    Console.WriteLine("*** UPDATE ***");
    foreach (var p in q)
    {
        p.UnitPrice += 1.00M;
    }

    //
    ChangeSet cs = db.GetChangeSet();
    Console.WriteLine("*** CHANGE SET ***");
    Console.WriteLine("Number of entities inserted: {0}", cs.Inserts.Count);
    Console.WriteLine("Number of entities updated:  {0}", cs.Updates.Count);
    Console.WriteLine("Number of entities deleted:  {0}", cs.Deletes.Count);
    Console.WriteLine();

    Console.WriteLine("*** GetOriginalEntityState ***");
    foreach (object o in cs.Updates)
    {
        Product p = o as Product;
        if (p != null)
        {
            Product oldP = db.Products.GetOriginalEntityState(p);
            Console.WriteLine("** Current **");
            ObjectDumper.Write(p);
            Console.WriteLine("** Original **");
            ObjectDumper.Write(oldP);
            Console.WriteLine();
        }
    }
    Console.WriteLine();

    Console.WriteLine("*** GetModifiedMembers ***");
    foreach (object o in cs.Updates)
    {
        Product p = o as Product;
        if (p != null)
        {
            foreach (ModifiedMemberInfo mmi in db.Products.GetModifiedMembers(p))
            {
                Console.WriteLine("Member {0}", mmi.Member.Name);
                Console.WriteLine("\tOriginal value: {0}", mmi.OriginalValue);
                Console.WriteLine("\tCurrent  value: {0}", mmi.CurrentValue);
            }
        }
    }

    db.SubmitChanges();

    Console.WriteLine();
    Console.WriteLine("*** AFTER ***");
    ObjectDumper.Write(q);

    Cleanup68();  // Restore previous database state
}

public void LinqToSqlInsert06() {
    Console.WriteLine("*** BEFORE ***");
    ObjectDumper.Write(from c in db.OrderDetails where c.OrderID == 10255 select c);


    Console.WriteLine();
    Console.WriteLine("*** DELETE ***");
    //Beverages
    OrderDetail orderDetail = db.OrderDetails.First(c => c.OrderID == 10255 && c.ProductID == 36);

    db.OrderDetails.DeleteOnSubmit(orderDetail);
    db.SubmitChanges();


    Console.WriteLine();
    Console.WriteLine("*** AFTER ***");
    ClearDBCache();
    ObjectDumper.Write(from c in db.OrderDetails where c.OrderID == 10255 select c);



    Cleanup69();  // Restore previous database state
}

delete one to many
public void LinqToSqlInsert07() {
    var orderDetails =
        from o in db.OrderDetails
        where o.Order.CustomerID == "WARTH" && o.Order.EmployeeID == 3
        select o;

    Console.WriteLine("*** BEFORE ***");
    ObjectDumper.Write(orderDetails);

    Console.WriteLine();
    Console.WriteLine("*** DELETE ***");
    var order =
        (from o in db.Orders
         where o.CustomerID == "WARTH" && o.EmployeeID == 3
         select o).First();

    foreach (OrderDetail od in orderDetails)
    {
        db.OrderDetails.DeleteOnSubmit(od);
    }

    db.Orders.DeleteOnSubmit(order);

    db.SubmitChanges();


    Console.WriteLine();
    Console.WriteLine("*** AFTER ***");
    ObjectDumper.Write(orderDetails);



    Cleanup70();  // Restore previous database state
}

where
public void LinqToSqlWhere01() {
    var q =
        from c in db.Customers
        where c.City == "London"
        select c;
    ObjectDumper.Write(q);
}

public void LinqToSqlWhere02() {
    var q =
        from e in db.Employees
        where e.HireDate >= new DateTime(1994, 1, 1)
        select e;

    ObjectDumper.Write(q);
}

first condition
public void LinqToSqlWhere08() {
    Order ord = db.Orders.First(o => o.Freight > 10.00M);
    ObjectDumper.Write(ord, 0);
}

public void LinqToSqlSelect01() {
    var q =
        from c in db.Customers
        select c.ContactName;

    ObjectDumper.Write(q);
}

public void LinqToSqlSelect04() {
    var q =
        from p in db.Products
        select new {p.ProductID, HalfPrice = p.UnitPrice / 2};
    ObjectDumper.Write(q, 1);
}

public void LinqToSqlSelect05() {
    var q =
        from p in db.Products
        select new {p.ProductName, Availability = p.UnitsInStock - p.UnitsOnOrder < 0 ? "Out Of Stock": "In Stock"};

    ObjectDumper.Write(q, 1);
}

public void LinqToSqlSelect10() {
    var q = (
        from c in db.Customers
        select c.City )
        .Distinct();

    ObjectDumper.Write(q);
}

public void LinqToSqlCount01() {
    var q = db.Customers.Count();
    Console.WriteLine(q);
}
public void LinqToSqlCount02() {
    var q = db.Products.Count(p => !p.Discontinued);
    Console.WriteLine(q);
}
public void LinqToSqlCount03() {
    var q = db.Orders.Select(o => o.Freight).Sum();
    Console.WriteLine(q);
}
public void LinqToSqlCount05() {
    var q = db.Products.Select(p => p.UnitPrice).Min();
    Console.WriteLine(q);
}
public void LinqToSqlCount07() {
    var categories =
        from p in db.Products
        group p by p.CategoryID into g
        select new {
            CategoryID = g.Key,
            CheapestProducts =
                from p2 in g
                where p2.UnitPrice == g.Min(p3 => p3.UnitPrice)
                select p2
        };

    ObjectDumper.Write(categories, 1);
}
public void LinqToSqlCount08() {
    var q = db.Employees.Select(e => e.HireDate).Max();
    Console.WriteLine(q);
}
public void LinqToSqlCount11() {
    var q = db.Orders.Select(o => o.Freight).Average();
    Console.WriteLine(q);
}
public void LinqToSqlCount12() {
    var q = db.Products.Average(p => p.UnitPrice);
    Console.WriteLine(q);
}
public void LinqToSqlCount13() {
    var categories =
        from p in db.Products
        group p by p.CategoryID into g
        select new {
            g.Key, 
            ExpensiveProducts =
                from p2 in g
                where p2.UnitPrice > g.Average(p3 => p3.UnitPrice)
                select p2
        };

    ObjectDumper.Write(categories, 1);
}

join
public void LinqToSqlJoin03() {
    var q =
        from e in db.Employees
        from et in e.EmployeeTerritories
        where e.City == "Seattle"
        select new {e.FirstName, e.LastName, et.Territory.TerritoryDescription};

    ObjectDumper.Write(q);
}
//self jon
public void LinqToSqlJoin04() {
    var q =
        from e1 in db.Employees
        from e2 in e1.Employees
        where e1.City == e2.City
        select new {
            FirstName1 = e1.FirstName, LastName1 = e1.LastName,
            FirstName2 = e2.FirstName, LastName2 = e2.LastName,
            e1.City
        };

    ObjectDumper.Write(q);
}
//group join 
public void LinqToSqlJoin05() {
    var q =
        from c in db.Customers
        join o in db.Orders on c.CustomerID equals o.CustomerID into orders
        select new {c.ContactName, OrderCount = orders.Count()};

    ObjectDumper.Write(q);
}
//left join
public void LinqToSqlJoin07() {
    var q =
        from e in db.Employees
        join o in db.Orders on e equals o.Employee into ords
        from o in ords.DefaultIfEmpty()
        select new {e.FirstName, e.LastName, Order = o};

    ObjectDumper.Write(q);
}

public void LinqToSqlPaging01() {
    var q = (
        from c in db.Customers
        orderby c.ContactName
        select c)
        .Skip(50)
        .Take(10);

    ObjectDumper.Write(q);
}