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• Linq to Entities and LEFT OUTER JOIN issue with MANY:1 relations

  - by Robert Koritnik

  Can somebody tell me, why does Linq to Entities translate many to 1 relationships to left outer join instead of inner join? Because there's referential constraint on DB itself that ensures there's a record in the right table, so inner join should be used instead (and it would work much faster) If relation was many to 0..1 left outer join would be correct. Question Is it possible to write LINQ in a way so it will translate to inner join rather than left outer join. It would speed query execution a lot... I haven't used eSQL before, but would it be wise to use it in instead of LINQ? Edit I updated my tags to include technology I'm using in the background: Entity Framework V1 Devart dotConnect for Mysql MySql database If someone could test if the same is true on Microsoft SQL server it would also give me some insight if this is Devart's issue or it's a general L2EF functionality... But I suspect EF is the culprit here.

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• Converting "is null" into a linq to sql statement

  - by Darryl Braaten

  I am having trouble replicating the following sql as a LINQ statement select TableA.* from TableA left outer join TableAinTableB on TableA.Id = TableAId where TableBId is null The following returns no lines from TableA in db.TableA join AinB in db.TableAinTableB on TableA.Id equals TableAId where AinB.TableBId == null select TableA Also tried and a few other things that didn't work. from TableA in db.TableA join AinB in db.TableAinTableB on TableA.Id equals TableAId where AinB == null select TableA TableAinTableB is a many to many table. The query I want will pull all the records from TableA that have no records in the middle table. My sql does what I want but I have no idea how to convert it to LINQ to SQL. I ended up working around it by just doing a db.ExecuteQuery("working sql"); But I would like to know if the query is possible in LINQ and how to write it, or a pointer to a document that covers this scenario. My searching did not uncover anything I found useful.

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• Unit Testing, IDataContext and Stored Procedures via Linq

  - by Terry_Brown

  hey folks, I'm currently using Stephen Walther's approach to unit testing Linq to SQL and the datacontext (http://stephenwalther.com/blog/archive/2008/08/17/asp-net-mvc-tip-33-unit-test-linq-to-sql.aspx) which is working a treat for all things linq. My Dal layer takes in an IDataContext, I use DI (via Unity) to concrete that up as the correct DataContext object and all works well. But - we have a company policy here of writes going via Stored Procs. Has anyone come up with a solution for mocking/faking the data context and still allowing stored procs to effectively be unit tested? I've got no real experience of any of the mocking frameworks (Rhino etc.) so if these are the correct means of doing this, I'd love some pointers on guides for them. Many thanks, Terry

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• Linq to sql Error "Data at the root level is invalid " for nullable xml column

  - by Mukesh

  I have Created a table like CREATE TABLE [dbo].[tab1]( [Id] [int] NOT NULL, [Name] [varchar](100) NOT NULL, [Meta] [xml] NULL, CONSTRAINT [PK_tab1] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY] When I am doing linq to sql query to fetch a data it throw an error "data at the root level is invalid linq". In further investigation I come to know that the meta column is null in that case. In real it is nullable Do I have to remove the nullable and set some blank root node as default or there is some another way to get rid of the error. My linq Query which throws error var obj1= (from obj in dbContext.tab1s where obj.id== 123 select obj).FirstOrDefault<Tab1>();

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• Linq and Lamba Expressions - while walking a selected list perform an action

  - by Prescott

  Hey, I'm very new to linq and lamba expressions. I'm trying to walk a collection, and when I find an item that meets some criteria I'd like to add that to another separate collection. My linq to walk the collection looks like this (this works fine): From i as MyCustomItem In MyCustomItemCollection Where i.Type = "SomeType" Select i I need each of the select items to then be added to a ListItemCollection, I know I can assign that linq query to a variable, and then do a for each loop adding a new ListItem to the collection, but I'm trying o find a way to add each item to the new ListItemcollection while walking, not a second loop. Thanks ~P

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• Easiest way to retrofit retry logic on LINQ to SQL migration to SQL Azure

  - by Pat James

  I have a couple of existing ASP .NET web forms and MVC applications that currently use LINQ to SQL with a SQL Server 2008 Express database on a Windows VPS: one VPS for both IIS and SQL. I am starting to outgrow the VPS's ability to effectively host both SQL and IIS and am getting ready to split them up. I am considering migrating the database to SQL Azure and keeping IIS on the VPS. After doing initial research it sounds like implementing retry logic in the data access layer is a must-do when adopting SQL Azure. I suspect this is even more critical to implement in my situation where IIS will be on a VPS outside of the Azure infrastructure. I am looking for pointers on how to do this with the least effort and impact on my existing code base. Is there a good retry pattern that can be applied once at the LINQ to SQL data access layer, as opposed to having to wrap all of my LINQ to SQL operations in try/catch/wait/retry logic?

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• LINQ to SQL Web Application Best Practices

  - by derek

  In my experience building web applications, I've always used a n-tier approach. A DAL that gets data from the db and populates the objects, and BLL that gets objects from the DAL and performs any business logic required on them, and the website that gets it's display data from the BLL. I've recently started learning LINQ, and most of the examples show the queries occurring right from the Web Application code-behinds(it's possible that I've only seen overly simplified examples). In the n-tier architectures, this was always seen as a big no-no. I'm a bit unsure of how to architect a new Web Application. I've been using the Server Explorer and dbml designer in VS2008 to create the dbml and object relationships. It seems a little unclear to me if the dbml would be considered the DAL layer, if the website should call methods within a BLL, which then would do the LINQ queries, etc. What are some general architecture best practices, or approaches to creating a Web Application solution using LINQ to SQL?

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• ASP.NET MVC 3 Linq uppercase or lowercase database search

  - by user1495557

  I need immediate help. ): and i know little english. ASP.NET MVC 3 Linq uppercase or lowercase contains search Example: string metin="baris"; var IcerikAra = (from icerik in Context.dbDokumanEditor join kategori in Context.dbDokumanKategori on icerik.KategoriID equals kategori.KategoriID where icerik.Icerik.toLower().Contains(metin) select new { KategoriID=kategori. KategoriAd=kategori.KategoriAd }).ToList(); Exception: StackTrace: at System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommandentityCommand, CommandBehavior behavior) at System.Data.Objects.Internal.ObjectQueryExecutionPlan.Execute[TResultType](ObjectContext context, ObjectParameterCollection parameterValues) at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable.GetEnumerator() at System.Data.Entity.Internal.Linq.InternalQuery`1.GetEnumerator() at System.Data.Entity.Infrastructure.DbQuery`1.System.Collections.Generic.IEnumerable.GetEnumerator() at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source) at Plus.Areas.DokumanEditor.Controllers.DokumanController.DokumanIcerikAramaBaslat(String metin) Error Message: An error occurred while executing the command definition. See the inner exception for details. thanks..

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• SImplifying with LINQ - Basic selection

  - by baron

  Hello foreach (var person in peopleList.Where(person => person.FirstName == "Messi")) { selectPeople.Add(person); } I am just wondering if there is any way to simplify this using LINQ. Like rather than look at all the people I was trying to use LINQ to just fill a list with the "Messi"'s... was trying something like... var selectPeople = peopleList.Select(x=>x.FirstName=="Messi"); Then I could just add everyone in that list without a check. But it doesn't quite work as planned. Maybe there's no point simplifying that expression. But the question seemed worthwhile just to strengthen my LINQ knowledge.

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• LINQ DataLoadOptions - Retrieval of data via Fulltext/Broken Foreign Key Relationship

  - by Alex

  I've hit a brick wall: I have an SQL Function: FUNCTION [dbo].[ContactsFTS] (@searchtext nvarchar(4000)) RETURNS TABLE AS RETURN SELECT * FROM Contacts INNER JOIN CONTAINSTABLE(Contacts, *, @searchtext) AS KEY_TBL ON Contacts.Id = KEY_TBL.[KEY] which I am calling via LINQ public IQueryable<ContactsFTSResult> SearchByFullText(String searchText) { return db.ContactsFTS(searchText); } I am projecting the ContactsFTSResult collection into a List<Contact> which is then given to my viewmodel. Here is the problem: My Contacts table (and therefore the Contact object created via LINQ to SQL) has multiple FK relationships to other information, such as Contact.BillingAddressId is an FK to an Address.Id. That information is missing after I do the fulltext search (e.g. if I try to access Contact.BillingAddress it is null). Can I add this information somehow via DataLoadOptions? I tried LoadWith<Contact>(c => c.BillingAddress) but this doesn't work, I assume because of the fact that I'm calling the function instead of doing the whole query via LINQ.

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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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