メソッド ベースのクエリ構文例: パーティション分割 (LINQ to Entities)
このトピックでは、クエリ式構文で、Skip メソッドおよび Take メソッドを使用して、AdventureWorks Sales Model を照会する例を取り上げます。 The AdventureWorks Sales Model used in these examples is built from the Contact, Address, Product, SalesOrderHeader, and SalesOrderDetail tables in the AdventureWorks sample database.
このトピックの例には、次の using/Imports ステートメントが使用されています。
Option Explicit On
Option Strict On
Imports System.Data.Objects
Imports System.Globalization
using System;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Objects;
using System.Globalization;
using System.Data.EntityClient;
using System.Data.SqlClient;
using System.Data.Common;
Skip
例
次の例では、Contact テーブルから最初の 5 つを除くすべての連絡先を、Skip メソッドを使って取得します。
Using context As New AdventureWorksEntities
'LINQ to Entities only supports Skip on ordered collections.
Dim products As IOrderedQueryable(Of Product) = _
context.Products.OrderBy(Function(p) p.ListPrice)
Dim allButFirst3Products As IQueryable(Of Product) = products.Skip(3)
Console.WriteLine("All but first 3 products:")
For Each product As Product In allButFirst3Products
Console.WriteLine("Name: {0} \t ID: {1}", _
product.Name, _
product.ProductID)
Next
End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
// LINQ to Entities only supports Skip on ordered collections.
IOrderedQueryable<Product> products = context.Products
.OrderBy(p => p.ListPrice);
IQueryable<Product> allButFirst3Products = products.Skip(3);
Console.WriteLine("All but first 3 products:");
foreach (Product product in allButFirst3Products)
{
Console.WriteLine("Name: {0} \t ID: {1}",
product.Name,
product.ProductID);
}
}
例
次の例では、Seattle から最初の 2 つを除くすべての住所を、Skip メソッドを使って取得します。
Using context As New AdventureWorksEntities
Dim orders As ObjectSet(Of SalesOrderHeader) = context.SalesOrderHeaders
Dim addresses As ObjectSet(Of Address) = context.Addresses
'LINQ to Entities only supports Skip on ordered collections.
Dim query = ( _
From address In addresses _
From order In orders _
Where address.AddressID = order.Address.AddressID _
And address.City = "Seattle" _
Order By order.SalesOrderID _
Select New With _
{ _
.City = address.City, _
.OrderID = order.SalesOrderID, _
.OrderDate = order.OrderDate _
}).Skip(2)
Console.WriteLine("All but first 2 orders in Seattle:")
For Each order In query
Console.WriteLine("City: {0} Order ID: {1} Total Due: {2:d}", _
order.City, order.OrderID, order.OrderDate)
Next
End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<Address> addresses = context.Addresses;
ObjectSet<SalesOrderHeader> orders = context.SalesOrderHeaders;
//LINQ to Entities only supports Skip on ordered collections.
var query = (
from address in addresses
from order in orders
where address.AddressID == order.Address.AddressID
&& address.City == "Seattle"
orderby order.SalesOrderID
select new
{
City = address.City,
OrderID = order.SalesOrderID,
OrderDate = order.OrderDate
}).Skip(2);
Console.WriteLine("All but first 2 orders in Seattle:");
foreach (var order in query)
{
Console.WriteLine("City: {0} Order ID: {1} Total Due: {2:d}",
order.City, order.OrderID, order.OrderDate);
}
Take
例
次の例では、Contact テーブルから最初の 5 つの連絡先だけを、Take メソッドを使って取得します。
Using context As New AdventureWorksEntities
Dim contacts As ObjectSet(Of Contact) = context.Contacts
Dim first5Contacts As IQueryable(Of Contact) = contacts.Take(5)
Console.WriteLine("First 5 contacts:")
For Each contact As Contact In first5Contacts
Console.WriteLine("Title = {0} " & vbTab & " FirstName = {1} " _
& vbTab & " Lastname = {2}", contact.Title, contact.FirstName, _
contact.LastName)
Next
End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
IQueryable<Contact> first5Contacts = context.Contacts.Take(5);
Console.WriteLine("First 5 contacts:");
foreach (Contact contact in first5Contacts)
{
Console.WriteLine("Title = {0} \t FirstName = {1} \t Lastname = {2}",
contact.Title,
contact.FirstName,
contact.LastName);
}
}
例
次の例では、Seattle から最初の 3 つの住所を、Take メソッドを使って取得します。
Dim city = "Seattle"
Using context As New AdventureWorksEntities
Dim orders As ObjectSet(Of SalesOrderHeader) = context.SalesOrderHeaders
Dim addresses As ObjectSet(Of Address) = context.Addresses
Dim query = ( _
From address In addresses _
From order In orders _
Where address.AddressID = order.Address.AddressID _
And address.City = city _
Select New With _
{ _
.City = address.City, _
.OrderID = order.SalesOrderID, _
.OrderDate = order.OrderDate _
}).Take(3)
Console.WriteLine("First 3 orders in Seattle:")
For Each order In query
Console.WriteLine("City: {0} Order ID: {1} Total Due: {2:d}", _
order.City, order.OrderID, order.OrderDate)
Next
End Using
String city = "Seattle";
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<Address> addresses = context.Addresses;
ObjectSet<SalesOrderHeader> orders = context.SalesOrderHeaders;
var query = (
from address in addresses
from order in orders
where address.AddressID == order.Address.AddressID
&& address.City == city
select new
{
City = address.City,
OrderID = order.SalesOrderID,
OrderDate = order.OrderDate
}).Take(3);
Console.WriteLine("First 3 orders in Seattle:");
foreach (var order in query)
{
Console.WriteLine("City: {0} Order ID: {1} Total Due: {2:d}",
order.City, order.OrderID, order.OrderDate);
}
}