如何使用 Skip 和 Take 方法通过使用查询表达式语法来查询-分区

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本主题中的示例演示如何使用 Skip 和 Take 方法通过使用查询表达式语法来查询 AdventureWorks 销售模型。这些示例中使用的 AdventureWorks 销售模型从 AdventureWorks 示例数据库中的 Contact、Address、Product、SalesOrderHeader 和 SalesOrderDetail 等表生成。

本主题中的示例使用以下 using / Imports 语句：

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;

跳过

示例

以下示例使用 Skip 方法以获取 Contact 表中除前五个联系人之外的所有联系人。

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);

}

示例

以下示例使用 Skip 方法以获取 Seattle 的前两个地址之外的所有地址。

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

示例

以下示例使用 Take 方法以只从 Contact 表中获取前五个联系人。

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);

}

示例

以下示例使用 Take 方法以获取 Seattle 的前三个地址。

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);

}

请参阅

LINQ to Entities 中的查询

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