how can i get the last element of a query?
Printed From: IdeaBlade
Category: DevForce
Forum Name: DevForce 2009
Forum Discription: For .NET 3.5
URL: http://www.ideablade.com/forum/forum_posts.asp?TID=1370
Printed Date: 28-Mar-2025 at 8:45am
Topic: how can i get the last element of a query?
Posted By: monkeyking
Subject: how can i get the last element of a query?
Date Posted: 08-Jul-2009 at 8:27pm
|
once I query from the DomainModelEntityManager, I get a set of data, how can i get the first and last element of that set of data?
|
Replies:
Posted By: GregD
Date Posted: 09-Jul-2009 at 11:44am
var query = _mgr.Customers.OrderBy(c => c.CompanyName);
Customer aCustomer = query.FirstOrNullEntity();
Console.WriteLine("First customer: {0}", aCustomer.CompanyName );
Customer anotherCustomer = query.ToList().LastOrDefault();
Console.WriteLine("Last customer: {0}", anotherCustomer.CompanyName);
The query must be forced to execute immediately for LastOrDefault(); hence the ToList() call for that one.
|
Posted By: monkeyking
Date Posted: 09-Jul-2009 at 5:47pm
|
but some time I don't have 'ToList()' method, how can I make it appear? it only has 'ToHashSet()' and others, no 'ToList()'!
|
Posted By: Suah
Date Posted: 19-Jul-2009 at 5:37pm
using System.Collections.Generic;
so it will appear , you may like to learn more csharp basic stuff
|
Posted By: monkeyking
Date Posted: 20-Jul-2009 at 7:08pm
|
i think this is advanced knowledge. thanks for replying
|
Posted By: monkeyking
Date Posted: 29-Jul-2009 at 4:47pm
|
no, I don't think that's soluction, even I include System.Collections.Generic, it still doesn't have 'ToList()' method.
|
Posted By: GregD
Date Posted: 30-Jul-2009 at 2:49pm
Originally posted by monkeyking
no, I don't think that's soluction, even I include System.Collections.Generic, it still doesn't have 'ToList()' method.
|
You need to reference the System.Core assembly in your project, and add using statements for System.Linq and System.Collections.Generic to your code file.
ToList() is required by the IEnumerable<T> interface (which is defined in System.Collections.Generic); therefore, any type that implements IEnumerable<T> will have an implementation of ToList(). This is true of our EntityQuery<T>. However, as you apply extension methods to a query, most such methods return a new query (using the prior one as input), and sometimes the return type can change. But anything that's an IEnumerable<T> (this includes EntityQuery<T>, IEntityQuery<T>, and IQueryable<T>) should provide ToList().
Note that under certain circumstances you can get the non-generic IEnumerable instead of IEnumerable<T>. In those cases you may be able to call the Cast() method on the IEnumerable to cast it to an IEnumerable<T>, which will have ToList().
|
|