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  • Performance concern when using LINQ "everywhere"?

    - by stiank81
    After upgrading to ReSharper5 it gives me even more useful tips on code improvements. One I see everywhere now is a tip to replace foreach-statements with LINQ queries. Take this example: private Ninja FindNinjaById(int ninjaId) { foreach (var ninja in Ninjas) { if (ninja.Id == ninjaId) return ninja; } return null; } This is suggested replaced with the following using LINQ: private Ninja FindNinjaById(int ninjaId) { return Ninjas.FirstOrDefault(ninja => ninja.Id == ninjaId); } This looks all fine, and I'm sure it's no problem regarding performance to replace this one foreach. But is it something I should do in general? Or might I run into performance problems with all these LINQ queries everywhere?

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  • Databinding multiple tables linq query to gridview?

    - by Curtis White
    My question is how can I display a linq query in a gridview that has data from multiple tables AND allow the user to edit some of the fields or delete the data from a single table? I'd like to do this with either a linqdatasource or a linq query. I'm aware I can set the e.Result to the query on the selecting event. I've also been able to build a custom databound control for displaying the linq relations (parent.child). However, I'm not sure how I can make this work with delete? I'm thinking I may need to handle the delete event with custom code.

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  • Linq to NHibernate using Queryable.Where predicate

    - by Groo
    I am querying an SQLite database using LINQ to NHibernate. Person is an entity containing an Id and a Name: public class Person { public Guid Id { get; private set; } public string Name { get; private set; } } Let's say my db table contains a single person whose name is "John". This test works as expected: var query = from item in session.Linq<Person>() where (item.Name == "Mike") select item; // no such entity should exist Assert.IsFalse(query.Any()); but this one fails: var query = from item in session.Linq<Person>() select item; query.Where(item => item.Name == "Mike"); // following line actually returns the // "John" entry Assert.IsFalse(query.Any()); What am I missing?

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  • LINQ query needs either ascending or descending in the same query

    - by Sir Psycho
    Is there anyway this code can be refactored? The only difference is the order by part. Idealy I'd like to use a delegate/lamda expression so the code is reusable but I don't know how to conditionally add and remove the query operators OrderBy and OrderByDescending var linq = new NorthwindDataContext(); var query1 = linq.Customers .Where(c => c.ContactName.StartsWith("a")) .SelectMany(cus=>cus.Orders) .OrderBy(ord => ord.OrderDate) .Select(ord => ord.CustomerID); var query2 = linq.Customers .Where(c => c.ContactName.StartsWith("a")) .SelectMany(cus => cus.Orders) .OrderByDescending(ord => ord.OrderDate) .Select(ord => ord.CustomerID);

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  • Linq ChangeConflictException (ASP.NET MVC) - occurs when submitting DataContext changes

    - by Alex
    System.Data.Linq.ChangeConflictException: 2 of X updates failed. at System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode) at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode) at PROJECT.Controllers.HomeController.ClickProc(Int32 id, String code, String n) This is what I get very often. This action is done thousands of times a day, and I get this exception about once every 5 seconds. From what I understand it happens when something changes in the database in the period between creating DataContext and updating it. Am I right? What's the problem here and how can I fix it?

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  • Inspection of Insert Statement When Using LINQ's SubmitChanges

    - by Code Sherpa
    Hi. I want to see what my insert statement would look like as if I was wiring up an text-based ADO.NET command. How do I do this? I have been following the below link: http://damieng.com/blog/2008/07/30/linq-to-sql-log-to-debug-window-file-memory-or-multiple-writers And have added the DebugTextWriter class to my project. So, now, in my code I have the following which doesn't really do anything and I don't think its right: using(WorkbookDataContext dc = _conn.GetContext()) { if(profile.ProfileId > 0) { dc.Profiles.Attach(profile, true); } else { dc.Profiles.InsertOnSubmit(profile); } dc.Log = new DebugTextWriter(); #if DEBUG dc.Log = new System.IO.StreamWriter("linq-to-sql.log") { AutoFlush = true }; #endif dc.SubmitChanges(); } Any ideas what I am doing wrong and/or how to inspect my LINQ insert statement correctly? Thanks

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  • Possible Performance Considerations using Linq to SQL Repositories

    - by Robert Harvey
    I have an ASP.NET MVC application that uses Linq to SQL repositories for all interactions with the database. To deal with data security, I do trimming to filter data to only those items to which the user has access. This occurs in several places: Data in list views Links in a menu bar A treeview on the left hand side containing links to content Role-based security A special security attribute, inheriting from AuthorizeAttribute, that implements content-based authorization on every controller method. Each of these places instantiates a repository, which opens a Linq to Sql DataContext and accesses the database. So, by my count, each request for a page access opens at least six separate Linq to SQL DataContexts. Should I be concerned about this from a performance perspective, and if so, what can be done to mitigate it?

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  • nHibernate Linq Projection

    - by Craig
    I am using the version 1.0 release of Linq for nHibernate. When I run the following linq statements I receive the error not a single-length projection: Surname I can find very few references to this on the web and looking into the source it says it should never occur! ClientID is a Int type and Surname is a string. When I comment out all the string fields in the projection and just leave ClientID it runs ok, but as soon as I add surname back it errors. var context = m_ClientRepository.Linq; var result = (from client in context from address in client.Addresses from contact in client.Contacts where client.Surname.StartsWith(surname) && client.GivenName.StartsWith(givenName) && contact.Value.StartsWith(phoneNumber) group client by new { client.ClientID, client.Surname, client.GivenName } into clientGroup select new ClientSearchDTO() { ClientID = clientGroup.Key.ClientID, Surname = clientGroup.Key.Surname, GivenName = clientGroup.Key.GivenName, Address = clientGroup.Max(x => x.Addresses.FirstOrDefault().Address), PhoneNumber = clientGroup.Max(x => x.Contacts.FirstOrDefault().Value) }) .Skip(Paging.FirstRecord(pageNumber)) .Take(5);

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  • LInq to SQL - Partial Class - C#

    - by Mark Comix
    Hi, I have a system with 2 different projects, one is called LINQ_Extensions and the other is ORM_Linq. On ORM_Linq i have the LINQ diagram with the SQL tables "converted" in clases. One of the Class is called "Tipos_Pago" In the other project i have another class (partial class) "Tipos_Pago". I want to use the method OnValidate to validate the properties include in the class "Tipos_Pago", so i create this partial class. In the 2 projects i put the same NameSpace "ORM_Linq"(I changed the NameSpace of the project "LINQ_Extensions" to have the same of the project "ORM_Linq") After those chages, Visual Studio give me this error: Error 1 No defining declaration found for implementing declaration of partial method 'ORM_Linq.Tipos_Pago.OnValidate(System.Data.Linq.ChangeAction)' C..\Tipos_Pago.cs 13 22 Extensiones_Linq I don't have any Idea of what happend, can someone help me? Thanks, sorry for my poor english This is the code in the partial class: namespace ORM_Linq { public partial class Tipos_Pago { partial void OnValidate(System.Data.Linq.ChangeAction action) { //Valid code } } }

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  • C# - LINQ Statements with OR clauses

    - by user70192
    Hello, I am trying to use LINQ to return a list of tasks that are in one of three states. These states are: 10 - Completed 11 - Incomplete 12 - Skipped The state is available through a property called "TaskStateID". I can do this in LINQ with just one state as shown here: var filteredTasks = from task in tasks select task; // Do stuff with filtered tasks string selectedComboBoxValue = GetFilterComboBoxValue(); if (selected ComboBoxValue == 3) { filteredTasks = filteredTasks.Where(p => p.TaskStateID == 10); // How do I use an 'OR' here to say p.TaskStateID == 10 OR p.TaskStateID == 11 OR p.TaskStateID == 12 } As shown in the comment above, how do I use an 'OR' in a LINQ statement to say p.TaskStateID == 10 OR p.TaskStateID == 11 OR p.TaskStateID == 12? Thank you

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  • Get Average Using LINQ

    - by obautista
    Hoping someone can help me with the LINQ syntax to calculate an average. For example, I have the following LINQ query: var rates = from rating in ctx.Rates where rating.Id == Id select new { UserId = rating.UserId, Rating = rating.Rating }; If 10 records are returned, I need to calculate average on the Rating field. It is defined as as a Double in my DB. I am using LINQ to EF. So I would be assigning the UserId, MiscId, and the Rating would be the average on the records returned. I am passing one object back to the client code.

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  • Simplest LINQ in C# troubleshooting.

    - by Jay
    I'm trying to learn a bit of LINQ but I'm having compile issues right off the bat. Is there any specific reason why this won't work? using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace HelloLINQ { class HelloLINQ { public static void Main() { Example1(); } public static void Example1() { var numbers = new int[] { 1, 5, 3, 7, 3, 8, 9, 3, 6, 6, 2 }; var under5 = from n in numbers select n; foreach (var n in under5) { Console.WriteLine(n); } } } } The error is: Could not find an implementation of the query pattern for source type 'int[]'. 'Select' not found. Are you missing a reference to 'System.Core.dll' or a using directive for 'System.Linq'?

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  • Using Linq on a Dataset

    - by JasonMHirst
    Can someone enlighthen me with regards to Linq please? I have a dataset that is populated via a SQL Stored Procedure, the format of which is below: Country | Brand | Variant | 2004 | 2005 | 2006 | 2007 | 2008 The number of rows varies between 50 and several thousand. What I'm trying to do is use Linq to interrogate the dataset (there will be several Linq queries based on user options), but a simple example would be to SUM the year columns based on Brand. I have the following that I believe creates a template for me to work with: But from here on I'm absolutely stuck! sqlDA.Fill(ds, "Profiler") Dim brandsQuery = From cust In ds.Tables(0).AsEnumerable() Select _BrandName = cust.Item("BrandName"), _y0 = cust.Item("1999"), _y1 = cust.Item("2004"), _y2 = cust.Item("2005"), _y3 = cust.Item("2006"), _y4 = cust.Item("2007"), _y5 = cust.Item("2008") I'm tried to look at examples, but can't see any that are VB.Net based and/or show me how to Sum/Group. Can someone please provide an example so I can perhaps learn from it. Thanks.

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  • Which data framework is better for an ASP.NET MVC site - LINQ to SQL or NHibernate

    - by Paul Alexander
    We're about to embark on some ASP.NET MVC development and have been using our own entity framework for years. However we need to support more than our entity framework is capable of and so I'd like to get some opinions about using MVC with a more robust framework. We have narrowed down or choices to either NHibernate (with the Fluent APIs) or LINQ to SQL. Which framework lends itself best to MVC style development (I know SO uses LINQ to SQL)? If we want to support SQL Server, Oracle, MySQL - does that exclude LINQ to SQL?

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  • Linq-to-SQL and Performance.

    - by jalpesh
    HI, I am developing asp.net mvc site with linq-to-sql we are having 1000 cocurrent users and we are having performance problems. I have found that stackovewflow is also build on linq-to-sql? So can anybody know how they improved performance. Without line performance was good each page are loaded in 3 seconds but after migrating to linq as per our client requirement page comes in 8 to 10 seconds which is not acceptable performance. Our HTML is very clear but we are having very complex database operations. Any tip or code will be best answer. Thanks in advance,

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  • Translate SQL to LINQ query - group/join/filter

    - by Paddy
    I have the following query: SELECT S.[FlowOrder], S.[DESCRIPTION], COUNT(I.ID) FROM WorkFlowStatus AS S INNER JOIN Item AS I ON S.ID = I.StatusID WHERE I.Installation = '1' GROUP BY S.[Description], S.[FlowOrder] ORDER BY S.[FlowOrder] Which gives me the count of an item, grouped by a foreign key to workflow, outputting the descriptive name from my FK table. I've go this far with the LINQ query (using LINQ-to-SQL) in the background: var items = from s in _entities.WorkflowStatus join i in _entities.Items on s.ID equals i.StatusId into Statuses orderby s.FlowOrder select new {s.Description, ItemCount = Statuses.Count() }; How do I get the where clause in the SQL into this LINQ query?

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  • How do I generate optimized SQL with my (added) partial methods on LINQ entities

    - by Ra
    Let's say I have a Person table with a FirstName and LastName column. I extended the Person LINQ entity class with a get property "FullName", that concatenates the first and last names. A LINQ query like: from person... select fullName where id = x generates SQL selecting all Patient columns, since FullName is evaluated after firing the query. I would like to limit the select clause to only the 2 columns required. This is a simple example, but the limitation it shows is that I cannot isolate my business/formatting rules but have to embed them in the LINQ query, so they're not reusable (since it is in the select part) or I need select both columns separately, and then concatenate them higher up in the data or business layer with static helper methods. Any ideas for a clean design using the entity partial classes or extensions? Thanks

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  • Comparing 2 linq applications: Unexpected result

    - by lukesky
    I drafted 2 ASP.NET applications using LINQ. One connects to MS SQL Server, another to some proprietary memory structure. Both applications work with tables of 3 int fields, having 500 000 records (the memory structure is identical to SQL Server table). The controls used are regular: GridView and ObjectDataSource. In the applications I calculate the average time needed for each paging click processing. LINQ + MS SQL application demands 0.1 sec per page change. LINQ + Memory Structure demands 0.8 sec per page change. This Is shocking result. Why the application handling data in memory works 8 times slower than the application using hard drive? Can anybody tell me why that happens?

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  • Linq query with Array in where clause?

    - by Matt Dell
    I have searched for this, but still can't seem to get this to work for me. I have an array of Id's associated with a user (their Organization Id). These are placed in an int[] as follows: int[] OrgIds = (from oh in this.Database.OrganizationsHierarchies join o in this.Database.Organizations on oh.OrganizationsId equals o.Id where (oh.Hierarchy.Contains(@OrgId)) || (oh.OrganizationsId == Id) select o.Id).ToArray(); The code there isn't very important, but it shows that I am getting an integer array from a Linq query. From this, though, I want to run another Linq query that gets a list of Personnel, that code is as follows: List<Personnel> query = (from p in this.Database.Personnels where (search the array) select p).ToList(); I want to add in the where clause a way to select only the users with the OrganizationId's in the array. So, in SQL where I would do something like "where OrganizationId = '12' or OrganizationId = '13' or OrganizatonId = '17'." Can I do this fairly easily in Linq / .NET?

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  • linq with Include and criteria

    - by JMarsch
    How would I translate this into LINQ? Say I have A parent table (Say, customers), and child (addresses). I want to return all of the Parents who have addresses in California, and just the california address. (but I want to do it in LINQ and get an object graph of Entity objects) Here's the old fashioned way: SELECT c.blah, a.blah FROM Customer c INNER JOIN Address a on c.CustomerId = a.CustomerId where a.State = 'CA' The problem I'm having with LINQ is that i need an object graph of concrete Entity types (and it can't be lazy loaded. Here's what I've tried so far: // this one doesn't filter the addresses -- I get the right customers, but I get all of their addresses, and not just the CA address object. from c in Customer.Include(c = c.Addresses) where c.Addresses.Any(a = a.State == "CA") select c // this one seems to work, but the Addresses collection on Customers is always null from c in Customer.Include(c = c.Addresses) from a in c.Addresses where a.State == "CA" select c; Any ideas?

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  • for vs. foreach vs. LINQ

    - by beccoblu
    When I write code in Visual Studio, ReSharper (God bless it!) often suggests me to change my old-school for loop in the more compact foreach form. And often, when I accept this change, ReSharper goes a step forward, and suggests me to change it again, in a shiny LINQ form. So, I wonder: are there some real advantages, in these improvements? In pretty simple code execution, I cannot see any speed boost (obviously), but I can see the code becoming less and less readable... So I wonder: is it worth it?

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  • Help regarding database and logic layer for my ASP.NET MVC application

    - by Ismail S
    I'm going to start a new project which is going to be small initially but may grow to big over the years. I'm strongly convinced that I'm going to use ASP.NET MVC with jQuery for UI. I want to go for MySQL as database for some reasons but worried on few things. I've a good years of experience working on SQL Server databases and on one project I've had a bad experience creating and managing stored procedures on MySQL database. I'm totally new to Linq but I see that it is easier to use once you are familiar with it. First thing is that accessing data should be easy. So I thought I should use MySQL to Linq but somewhere I read that it is not directly supported but MySQL .NET connector adds support for EntityFramework. I don't know what are the pros and cons of it. I would love if I can implement repository pattern. Will it be possible if I use Entity Framework? I'm not clear on how I should go about all this or I should just forget every thing and directly use SQL to Linq on SQL Server. I'm also concerned about the performance. Someone told me that if we use Entity framework it fetches lot of data and then filter it. Is that right?

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  • NHibernate Linq Timeout

    - by DarrenMcD
    How do I increase the timeout in NHibernate Linq To Sql? Not the Connection Timeout but the ado command timeout. using (ISession session = NHibernateHelper.OpenSession(NHibernateHelper.Databases.CarrierCDR)) using (session.BeginTransaction(IsolationLevel.ReadUncommitted)) { lCdrs = (from verizon in session.Linq<Domain.Verizon>() where verizon.Research == true && verizon.ReferenceTable == null orderby verizon.CallBillingDate descending select verizon).ToList(); }

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  • LINQ to XML vs. XmlReader

    - by Vadim
    In my Silverlight application I'm using mostly XmlReader but I'm playing with idea to replace XmlReader implementation with LINQ to XML. What are pros and cons between LINQ to XML and XmlReader in Silverlight?

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