查询表达式语法示例：排序 (LINQ to DataSet)
更新：November 2007
本主题中的示例演示如何使用 OrderBy、OrderByDescending、Reverse<TSource> 和 ThenByDescending 方法来查询 DataSet 并使用查询表达式语法对结果排序。
这些示例中所使用的 FillDataSet 方法已在 向数据集中加载数据 中指定。
本主题中的示例使用 AdventureWorks 示例数据库中的 Contact、Address、Product、SalesOrderHeader 和 SalesOrderDetail 表。
本主题中的示例使用下面的 using/Imports 语句：
Option Explicit On
Imports System
Imports System.Linq
Imports System.Linq.Expressions
Imports System.Collections.Generic
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.Common
Imports System.Globalization
using System;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Data.Common;
using System.Globalization;
有关更多信息，请参见如何：在 Visual Studio 中创建 LINQ to DataSet 项目。
OrderBy
示例
此示例使用 OrderBy 返回按姓氏排序的联系人列表。
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim contacts As DataTable = ds.Tables("Contact")
Dim query = _
From contact In contacts.AsEnumerable() _
Select contact _
Order By contact.Field(Of String)("LastName")
Console.WriteLine("The sorted list of last names:")
For Each contact In query
Console.WriteLine(contact.Field(Of String)("LastName"))
Next
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable contacts = ds.Tables["Contact"];
IEnumerable<DataRow> query =
from contact in contacts.AsEnumerable()
orderby contact.Field<string>("LastName")
select contact;
Console.WriteLine("The sorted list of last names:");
foreach (DataRow contact in query)
{
Console.WriteLine(contact.Field<string>("LastName"));
}
示例
此示例使用 OrderBy 按姓氏的长度对联系人列表排序。
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim contacts As DataTable = ds.Tables("Contact")
Dim query = _
From contact In contacts.AsEnumerable() _
Select contact _
Order By contact.Field(Of String)("LastName").Length
Console.WriteLine("The sorted list of last names (by length):")
For Each contact In query
Console.WriteLine(contact.Field(Of String)("LastName"))
Next
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable contacts = ds.Tables["Contact"];
IEnumerable<DataRow> query =
from contact in contacts.AsEnumerable()
orderby contact.Field<string>("LastName").Length
select contact;
Console.WriteLine("The sorted list of last names (by length):");
foreach (DataRow contact in query)
{
Console.WriteLine(contact.Field<string>("LastName"));
}
OrderByDescending
示例
此示例使用等效于 OrderByDescending 方法的 orderby… descending (Order By … Descending) 从高到低排序价格列表。
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim products As DataTable = ds.Tables("Product")
Dim query = _
From product In products.AsEnumerable() _
Select product _
Order By product.Field(Of Decimal)("ListPrice") Descending
Console.WriteLine("The list price From highest to lowest:")
For Each product In query
Console.WriteLine(product.Field(Of Decimal)("ListPrice"))
Next
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable products = ds.Tables["Product"];
IEnumerable<Decimal> query =
from product in products.AsEnumerable()
orderby product.Field<Decimal>("ListPrice") descending
select product.Field<Decimal>("ListPrice");
Console.WriteLine("The list price from highest to lowest:");
foreach (Decimal product in query)
{
Console.WriteLine(product);
}
Reverse
示例
此示例使用 Reverse<TSource> 创建 OrderDate 早于 2002 年 2 月 20 日的订单的列表。
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim orders As DataTable = ds.Tables("SalesOrderHeader")
Dim query = ( _
From order In orders.AsEnumerable() _
Where order.Field(Of DateTime)("OrderDate") < New DateTime(2002, 2, 20) _
Select order).Reverse()
Console.WriteLine("A backwards list of orders where OrderDate < Feb 20, 2002")
For Each order In query
Console.WriteLine(order.Field(Of DateTime)("OrderDate"))
Next
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable orders = ds.Tables["SalesOrderHeader"];
IEnumerable<DataRow> query = (
from order in orders.AsEnumerable()
where order.Field<DateTime>("OrderDate") < new DateTime(2002, 02, 20)
select order).Reverse();
Console.WriteLine("A backwards list of orders where OrderDate < Feb 20, 2002");
foreach (DataRow order in query)
{
Console.WriteLine(order.Field<DateTime>("OrderDate"));
}
ThenByDescending
示例
此示例使用等效于 ThenByDescending 方法的 OrderBy… Descending 先按名称然后按定价从高到低对产品列表排序。
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim products As DataTable = ds.Tables("Product")
Dim query = _
From product In products.AsEnumerable() _
Order By product.Field(Of String)("Name"), _
product.Field(Of Decimal)("ListPrice") Descending _
Select product
For Each product In query
Console.Write("Product ID: " & product.Field(Of Integer)("ProductID"))
Console.Write(" Product Name: " & product.Field(Of String)("Name"))
Console.WriteLine(" List Price: " & product.Field(Of Decimal)("ListPrice"))
Next
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable products = ds.Tables["Product"];
IEnumerable<DataRow> query =
from product in products.AsEnumerable()
orderby product.Field<string>("Name"),
product.Field<Decimal>("ListPrice") descending
select product;
foreach (DataRow product in query)
{
Console.WriteLine("Product ID: {0} Product Name: {1} List Price {2}",
product.Field<int>("ProductID"),
product.Field<string>("Name"),
product.Field<Decimal>("ListPrice"));
}