本主题介绍如何对查询结果进行排序。本示例返回 Contact 对象的集合,其结果按 Contact.LastName 首字母的字母顺序排序。下面使用以下 实体框架 查询技术演示同一示例:
LINQ to Entities
Entity SQL with ObjectQuery<T>
ObjectQuery <T> 的查询生成器方法
本主题中的示例基于 Adventure Works 销售模型。若要运行本示例中的代码,必须已将 AdventureWorks 销售模型添加到您的项目中,并将项目配置为使用实体框架。为此,请完成如何:手动配置实体框架项目和如何:手动定义实体数据模型(实体框架) 中的过程。也可以使用实体数据模型向导定义 AdventureWorks 销售模型。有关更多信息,请参见如何:使用实体数据模型向导(实体框架)。
示例
以下是 LINQ to Entities 示例。
Using context As AdventureWorksEntities = _
New AdventureWorksEntities()
Try
' Define a query that returns a list
' of Contact objects sorted by last name.
Dim sortedNames = _
From n In context.Contact _
Order By n.LastName _
Select n
Console.WriteLine("The sorted list of last names:")
For Each name As Contact In sortedNames
Console.WriteLine(name.LastName)
Next
Catch ex As EntitySqlException
Console.WriteLine(ex.ToString())
End Try
End Using
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
try
{
// Define a query that returns a list
// of Contact objects sorted by last name.
var sortedNames =
from n in context.Contact
orderby n.LastName
select n;
Console.WriteLine("The sorted list of last names:");
foreach (Contact name in sortedNames)
{
Console.WriteLine(name.LastName);
}
}
catch (EntitySqlException ex)
{
Console.WriteLine(ex.ToString());
}
}
以下是 Entity SQL 示例。
' Define the Entity SQL query string that returns
' Contact objects sorted by last name.
Dim queryString As String = "SELECT VALUE n FROM Contact AS n " _
+ "Order By n.LastName"
Using context As AdventureWorksEntities = _
New AdventureWorksEntities()
Try
' Define an ObjectQuery that returns a collection
' of Contact objects sorted by last name.
Dim query As ObjectQuery(Of Contact) = _
New ObjectQuery(Of Contact)(queryString, context)
Console.WriteLine("The sorted list of last names:")
For Each name As Contact _
In query.Execute(MergeOption.AppendOnly)
Console.WriteLine(name.LastName)
Next
Catch ex As EntitySqlException
Console.WriteLine(ex.ToString())
End Try
End Using
// Define the Entity SQL query string that returns
// Contact objects sorted by last name.
string queryString = @"SELECT VALUE n FROM Contact AS n
Order By n.LastName";
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
try
{
// Define an ObjectQuery that returns a collection
// of Contact objects sorted by last name.
ObjectQuery<Contact> query =
new ObjectQuery<Contact>(queryString, context);
Console.WriteLine("The sorted list of last names:");
foreach (Contact name in query.Execute(MergeOption.AppendOnly))
{
Console.WriteLine(name.LastName);
}
}
catch (EntitySqlException ex)
{
Console.WriteLine(ex.ToString());
}
}
以下是查询生成器方法示例。
Using context As AdventureWorksEntities = _
New AdventureWorksEntities()
Try
' Define an ObjectQuery that returns a collection
' of Contact objects sorted by last name.
Dim query As ObjectQuery(Of Contact) = _
context.Contact.OrderBy("it.LastName")
Console.WriteLine("The sorted list of last names:")
For Each name As Contact _
In query.Execute(MergeOption.AppendOnly)
Console.WriteLine(name.LastName)
Next
Catch ex As EntitySqlException
Console.WriteLine(ex.ToString())
End Try
End Using
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
try
{
// Define an ObjectQuery that returns a collection
// of Contact objects sorted by last name.
ObjectQuery<Contact> query =
context.Contact.OrderBy("it.LastName");
Console.WriteLine("The sorted list of last names:");
foreach (Contact name in query.Execute(MergeOption.AppendOnly))
{
Console.WriteLine(name.LastName);
}
}
catch (EntitySqlException ex)
{
Console.WriteLine(ex.ToString());
}
}