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  • LINQ to SQL associations - how to change the value of associated field

    - by HAdes
    I have 2 classes with a LINQ association between them i.e.: Table1: Table2: ID ID Name Description ForiegnID The association here is between Table1.ID - Table2.ForiegnID I need to be able to change the value of Table2.ForiegnID, however I can't and think it is because of the association (as when I remove it, it works). Therefore, does anyone know how I can change the value of the associated field Table2.ForiegnID? Thanks.

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  • Stored Functions with Linq to Entities

    - by Lawnmower
    Hi, How can I make a MS-SQL stored function availabe in LINQ expressions if using the Entity framework? The SQL function was created with CREATE FUNCTION MyFunction(@name) ...). I was hoping to access it similarly to this: var data = from c in entities.Users where MyFunction(c.name) = 3; Unfortunately I have only .NET 3.5 available.

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  • Encrypt column data with LINQ

    - by kape123
    I was wondering if there is easy solution to this or I'm stuck with following: When updating DB: dti.Pass = Crypter.Encrypt(dti.Pass); _db.SubmitChanges(); When selecting from DB: Data.DbTableItem dti = _db.Single(a=a.Id == id); dti.Pass = Crypter.Decrypt(dti.Pass); Meaning - I am not really into writing repetitive code and this seems like logical thing to be supported by LINQ; so I'm wondering if it is.

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  • LinQ: Add list to a list

    - by JohannesBoersma
    I have the following code: var columnNames = (from autoExport in dataContext.AutoExports where autoExport.AutoExportTemplate != null && ContainsColumn(autoExport.AutoExportTemplate, realName) select GetDbColumnNames(autoExport.AutoExportTemplate, realName)).ToList(); Where the function GetDbColumns() returns an List<string>. So columNames is of the type List<List<string>>. Is it possible to create a List<string>, so each element of the list of GetDbColumns is added to the result of the LinQ query?

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  • How do I properly use LINQ with MySQL?

    - by Arda Xi
    I've been looking this up on Google for hours, but I haven't found anything conclusive. So far, I've seen a few paid options, an option with NHibernate, but most are marked as unstable or in production. Is there a stable implementation of LINQ for MySQL?

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  • Linq with EF dynamic search

    - by malik
    I am using EF 3.5 with MVC. I want to made a search page, has some fields for criteria like date, int etc. What is the way in linq to entities to filter the result dynamically. If there are one parameter we can use .where(a=a.id==1) but many combination with optional param how can i load results and then pass to model.

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  • compiling a linq to sql query

    - by frenchie
    Hi, I have queries that are built like this: public static List<MyObjectModel> GetData (int MyParam) { using (DataModel MyModelDC = new DataModel()) { var MyQuery = from.... select MyObjectModel { ...} } return new List<MyObjectModel> (MyQuery) } } It seems that using compiled linq-to-sql queries are about as fast as stored procedures and so the goal is to convert these queries into compiled queries. What's the syntax for this? Thanks.

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  • Order by descending based on condition

    - by Vinni
    Hello All, I want to write a LINQ to Entity query which does order by ascending or descending based on input parameter, Is there any way for that. Following is the my code. Please suggest. public List<Hosters_HostingProviderDetail> GetPendingApproval(SortOrder sortOrder) { List<Hosters_HostingProviderDetail> returnList = new List<Hosters_HostingProviderDetail>(); int pendingStateId = Convert.ToInt32(State.Pending); //If the sort order is ascending if (sortOrder == SortOrder.ASC) { var hosters = from e in context.Hosters_HostingProviderDetail where e.ActiveStatusID == pendingStateId orderby e.HostingProviderName ascending select e; returnList = hosters.ToList<Hosters_HostingProviderDetail>(); return returnList; } else { var hosters = from e in context.Hosters_HostingProviderDetail where e.StateID == pendingStateId orderby e.HostingProviderName descending select e; returnList = hosters.ToList<Hosters_HostingProviderDetail>(); return returnList; } }

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  • Repository vs Data Access

    - by vdh_ant
    Hi guys In the context of the n-tier application, is there a difference between what you would consider your data access classes to be and your repositories? I tend to think yes but I just wanted to see what other thought. My thinking is that the job of the repository is just to contain and execute the raw query itself, where as the data access class would create the context, execute the repository (passing in the context), handle mapping the data model to the domain model and return the result back up... What do you guys think? Also do you see any of this changing in a Linq to XML scenario (assuming that you change the context for the relevant XDocument)? Cheers Anthony

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  • how to order a group result with Linq?

    - by Aaron
    How can I order the results from "group ... by... into..." statement in linq? For instance: var queryResult = from records in container.tableWhatever where records.Time >= DateTime.Today group records by tableWhatever.tableHeader.UserId into userRecords select new { UserID = userRecords.Key, Records = userRecords }; The query returns records in table "contain.tableWhatever" grouped by "UserId". I want the returned results within each group ordered by time decending. How can I do that? More specific, assume the above query return only one group like the following: {UserID = 1, Records= {name1 5/3/2010_7:10pm; name2 5/3/2010_8:10pm; name3 5/3/2010_9:10pm} } After insert the orderby statement in the above query, the returned results should be like this: {UserID = 1, Records= {name3 5/3/2010_9:10pm; name2 5/3/2010_8:10pm; name1 5/3/2010_7:10pm} } Thanks for help!

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  • Using Dynamic LINQ to get a filter for my Web API

    - by Espo
    We are considering using the Dynamic.CS linq-sample included in the "Samples" directory of visual studio 2008 for our WebAPI project to allow clients to query our data. The interface would be something like this (In addition to the normal GET-methods): public HttpResponseMessage List(string filter = null); The plan is to use the dynamic library to parse the "filter"-variable and then execute the query agains the DB. Any thoughts if this is a good idea? Is it a security problem?

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  • linq to sql -> join

    - by ile
    SQL query: SELECT ArticleCategories.Title AS Category, Articles.Title, Articles.[Content], Articles.Date FROM ArticleCategories INNER JOIN Articles ON ArticleCategories.CategoryID = Articles.CategoryID Object repository: public class ArticleRepository { private DB db = new DB(); // // Query Methods public IQueryable<Article> FindAllArticles() { var result = from category in db.ArticleCategories join article in db.Articles on category.CategoryID equals article.CategoryID select new { CategoryID = category.CategoryID, CategoryTitle = category.Title, ArticleID = article.ArticleID, ArticleTitle = article.Title, ArticleDate = article.Date, ArticleContent = article.Content }; return result; } .... } And finally, I get this error: Error 1 Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Linq.IQueryable'. An explicit conversion exists (are you missing a cast?) C:\Documents and Settings\ilija\My Documents\Visual Studio 2008\Projects\CMS\CMS\Models\ArticleRepository.cs 29 20 CMS Any idea what did I do wrong? Thanks, Ile

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  • ASP.Net Entity Framework Repository & Linq

    - by Chris Klepeis
    My scenario: This is an ASP.NET 4.0 web app programmed via C# I implement a repository pattern. My repositorys all share the same ObjectContext, which is stored in httpContext.Items. Each repository creates a new ObjectSet of type E. Heres some code from my repository: public class Repository<E> : IRepository<E>, IDisposable where E : class { private DataModelContainer _context = ContextHelper<DataModelContainer>.GetCurrentContext(); private IObjectSet<E> _objectSet; private IObjectSet<E> objectSet { get { if (_objectSet == null) { _objectSet = this._context.CreateObjectSet<E>(); } return _objectSet; } } public IQueryable<E> GetQuery() { return objectSet; } Lets say I have 2 repositorys, 1 for states and 1 for countrys and want to create a linq query against both. Note that I use POCO classes with the entity framework. State and Country are 2 of these POCO classes. Repository stateRepo = new Repository<State>(); Repository countryRepo = new Repository<Country>(); IEnumerable<State> states = (from s in _stateRepo.GetQuery() join c in _countryRepo.GetQuery() on s.countryID equals c.countryID select s).ToList(); Debug.WriteLine(states.First().Country.country) essentially, I want to retrieve the state and the related country entity. The query only returns the state data... and I get a null argument exception on the Debug.WriteLine LazyLoading is disabled in my .edmx... thats the way I want it.

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  • Linq - Orderby not ordering

    - by Billy Logan
    Hello everyone, I have a linq query that for whatever reason is not coming back ordered as i would expect it to. Can anyone point me in the right direction as to why and what i am doing wrong? Code is as follows: List<TBLDESIGNER> designer = null; using (SOAE strikeOffContext = new SOAE()) { //Invoke the query designer = AdminDelegates.selectDesignerDesigns.Invoke(strikeOffContext).ByActive(active).ByAdmin(admin).ToList(); } Delegate: public static Func<SOAE, IQueryable<TBLDESIGNER>> selectDesignerDesigns = CompiledQuery.Compile<SOAE, IQueryable<TBLDESIGNER>>( (designer) => from c in designer.TBLDESIGNER.Include("TBLDESIGN") orderby c.FIRST_NAME ascending select c); Filter ByActive: public static IQueryable<TBLDESIGNER> ByActive(this IQueryable<TBLDESIGNER> qry, bool active) { //Return the filtered IQueryable object return from c in qry where c.ACTIVE == active select c; } Filter ByAdmin: public static IQueryable<TBLDESIGNER> ByAdmin(this IQueryable<TBLDESIGNER> qry, bool admin) { //Return the filtered IQueryable object return from c in qry where c.SITE_ADMIN == admin select c; } Wondering if the filtering has anything to do with it?? Thanks in advance, Billy

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  • Instantiate object from Linq to XML Query

    - by objectsbinding
    Hi All I have the following class public class CountrySpecificPIIEntity { public string Country { get; set; } public string CreditCardType { get; set; } public String Api { get; set; } public List<String> FilterList { get; set; } } I am trying to use a linq to XMl query to create a list of instances of type CountrySpecificPIIEntity. The XML is as below <piisettings> <country countrycode="DE"> <creditcardype credicardtype="mastercard"> <api api="INSERT_FILTERS"> <filters> <filter>FIRSTNAME</filter> <filter>HOUSENUMBER</filter> <filter>ADDITIONALADDRESSINFO</filter> <filter>EMAIL</filter> </filters> </api> </creditcardype> <creditcardype credicardtype="visa"> <api api="INSERT_FILTERS"> <filters> <filter>STATE</filter> <filter>EMAIL</filter> </filters> </api> </creditcardype> <creditcardype credicardtype="visa"> <api api="UPDATE_FILTERS"> <filters> <filter>STATE</filter> <filter>EMAIL</filter> </filters> </api> </creditcardype> </country> <country countrycode="GB"> <creditcardype credicardtype="americanexpress"> <api api="INSERT_FILTERS"> <filters> <filter>STREET</filter> <filter>ZIP</filter> <filter>CITY</filter> <filter>STATE</filter> <filter>EMAIL</filter> </filters> </api> </creditcardype> <creditcardype credicardtype="debank"> <api api="INSERT_FILTERS"> <filters> <filter>IPADDRESSCUSTOMER</filter> <filter>FIRSTNAME</filter> <filter>SURNAME</filter> <filter>HOUSENUMBER</filter> <filter>STREET</filter> <filter>ZIP</filter> <filter>CITY</filter> <filter>STATE</filter> <filter>EMAIL</filter> </filters> </api> </creditcardype> </country> </piisettings> what should the Linq to XML query be?

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  • nested linq-to-sql queries

    - by ile
    var result = ( from contact in db.Contacts join user in db.Users on contact.CreatedByUserID equals user.UserID orderby contact.ContactID descending select new ContactListView { ContactID = contact.ContactID, FirstName = contact.FirstName, LastName = contact.LastName, Company = (from field in contact.XmlFields.Descendants("Company") select field.Value).SingleOrDefault().ToString() }).Take(10); Here I described how my database tables look like. So, contacts table has one field that is xml type. In that field is stored Company filename and I need to read it. I tried it using this way: Company = (from field in contact.XmlFields.Descendants("Company") select field.Value).SingleOrDefault().ToString() }).Take(10); but I get following error: Member access 'System.String Value' of 'System.Xml.Linq.XElement' not legal on type 'System.Collections.Generic.IEnumerable`1[System.Xml.Linq.XElement]. Any solution for this? Thanks in advance, Ile

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  • Weighted Average with LINQ

    - by jsmith
    My goal is to get a weighted average from one table, based on another tables primary key. Example Data: Table1 Key WEIGHTED_AVERAGE 0200 0 Table2 ForeignKey LENGTH PCR 0200 105 52 0200 105 60 0200 105 54 0200 105 -1 0200 47 55 I need to get a weighted average based on the length of a segment and I need to ignore values of -1. I know how to do this in SQL, but my goal is to do this in LINQ. It looks something like this in SQL: SELECT Sum(t2.PCR*t2.LENGTH)/Sum(t2.LENGTH) AS WEIGHTED_AVERAGE FROM Table1 t1, Table2 t2 WHERE t2.PCR <> -1 AND t2.ForeinKey = t1.Key; I am still pretty new to LINQ, and having a hard time figuring out how I would translate this. The result weighted average should come out to roughly 55.3. Thank you.

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  • LINQ - 'Could not translate expression' with previously used and proven query condition

    - by tomfumb
    I am fairly new to LINQ and can't get my head around some inconsistency in behaviour. Any knowledgeable input would be much appreciated. I see similar issues on SO and elsewhere but they don't seem to help. I have a very simple setup - a company table and an addresses table. Each company can have 0 or more addresses, and if 0 one must be specified as the main address. I'm trying to handle the cases where there are 0 addresses, using an outer join and altering the select statement accordingly. Please note I'm currently binding the output straight to a GridView so I would like to keep all processing within the query. The following DOES work IQueryable query = from comp in context.Companies join addr in context.Addresses on comp.CompanyID equals addr.CompanyID into outer // outer join companies to addresses table to include companies with no address from addr in outer.DefaultIfEmpty() where (addr.IsMain == null ? true : addr.IsMain) == true // if a company has no address ensure it is not ruled out by the IsMain condition - default to true if null select new { comp.CompanyID, comp.Name, AddressID = (addr.AddressID == null ? -1 : addr.AddressID), // use -1 to represent a company that has no addresses MainAddress = String.Format("{0}, {1}, {2} {3} ({4})", addr.Address1, addr.City, addr.Region, addr.PostalCode, addr.Country) }; but this displays an empty address in the GridView as ", , ()" So I updated the MainAddress field to be MainAddress = (addr.AddressID == null ? "" : String.Format("{0}, {1}, {2} {3} ({4})", addr.Address1, addr.City, addr.Region, addr.PostalCode, addr.Country)) and now I'm getting the Could not translate expression error and a bunch of spewey auto-generated code in the error which means very little to me. The condition I added to MainAddress is no different to the working condition on AddressID, so can anybody tell me what's going on here? Any help greatly appreciated.

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  • Why is the use of abstractions (such as LINQ) so taboo?

    - by Matthew Patrick Cashatt
    I am an independent contractor and, as such, I interview 3-4 times a year for new gigs. I am in the midst of that cycle now and got turned down for an opportunity even though I felt like the interview went well. The same thing has happened to me a couple of times this year. Now, I am not a perfect guy and I don't expect to be a good fit for every organization. That said, my batting average is lower than usual so I politely asked my last interviewer for some constructive feedback, and he delivered! The main thing, according to the interviewer, was that I seemed to lean too much towards the use of abstractions (such as LINQ) rather than towards lower-level, organically grown algorithms. On the surface, this makes sense--in fact, it made the other rejections make sense too because I blabbed about LINQ in those interviews as well and it didn't seem that the interviewers knew much about LINQ (even though they were .NET guys). So now I am left with this question: If we are supposed to be "standing on the shoulders of giants" and using abstractions that are available to us (like LINQ), then why do some folks consider it so taboo? Doesn't it make sense to pull code "off the shelf" if it accomplishes the same goals without extra cost? It would seem to me that LINQ, even if it is an abstraction, is simply an abstraction of all the same algorithms one would write to accomplish exactly the same end. Only a performance test could tell you if your custom approach was better, but if something like LINQ met the requirements, why bother writing your own classes in the first place? I don't mean to focus on LINQ here. I am sure that the JAVA world has something comparable, I just would like to know why some folks get so uncomfortable with the idea of using an abstraction that they themselves did not write. UPDATE As Euphoric pointed out, there isn't anything comparable to LINQ in the Java world. So, if you are developing on the .NET stack, why not always try and make use of it? Is it possible that people just don't fully understand what it does?

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  • Are there any good resources for refactoring existing C# code to use LINQ while keeping your tests passing?

    - by Paddyslacker
    I've been teaching myself a little LINQ and an exercise I thought would be useful was to take my existing Project Euler C# code, which I built using Test Driven Development and gradually convert it to LINQ. I realise that LINQ is not always the best solution for all of the Project Euler problems, but I don't want to get into that here. I'm wondering whether or not it's feasible to refactor "traditional" OO C# code to use LINQ and functional programming syntax whilst keeping all of your tests passing. I can't find a way to make the tiny steps I'm used to making using TDD when converting to LINQ and this is a roadblock for me. I seem to have to make large changes to come up with a single function that I then replace whole chunks of my code with. I realise I could write this from scratch in LINQ, but in the real world, I'd like to be able to replace parts of my existing C# code to take advantage of LINQ where appropriate. Has anyone been successful with this approach? What resources did you find useful for refactoring existing C# code to use LINQ whilst taking a Test Driven Development approach?

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  • SQL SERVER – Monday Morning Puzzle – Query Returns Results Sometimes but Not Always

    - by pinaldave
    The amount of email I receive sometime it is impossible for me to answer every email. Nonetheless I try to answer pretty much every email I receive. However, quite often I receive such questions in email that I have no answer to them because either emails are not complete or they are out of my domain expertise. In recent times I received one email which had only one or two lines but indeed attracted my attention to it. The question was bit vague but it indeed made me think. The answer was not straightforward so I had to keep on writing the answer as I remember it. However, after writing the answer I do not feel satisfied. Let me put this question in front of you and see if we all can come up with a comprehensive answer. Question: I am beginner with SQL Server. I have one query, it sometime returns a result and sometime it does not return me the result. Where should I start looking for a solution and what kind of information I should send to you so you can help me with solving. I have no clue, please guide me. Well, if you read the question, it is indeed incomplete and it does not contain much of the information at all. I decided to help him and here is the answer, which I started to compose. Answer: As there are not much information in the original question, I am not confident what will solve your problem. However, here are the few things which you can try to look at and see if that solves your problem. Check parameter which is passed to the query. Is the parameter changing at various executions? Check connection string – is there some kind of logic around it? Do you have a non-deterministic component in your query logic? (In other words – does your result is based on current date time or any other time based function?) Are you facing time out while running your query? Is there any error in error log? What is the business logic in your query? Do you have all the valid permissions to all the objects used in the query? Are permissions changing or query accessing a different object in various executions? (Add your suggestions here) Meanwhile, have you ever faced this situation? If yes, do share your experience in the comment area. I will send a copy of my book SQL Server Interview Questions and Answers to one of the most interesting comment. The winner will be announced by next Monday.  Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Interview Questions and Answers, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Linq2sql code generator misbehaving

    - by Martin
    Sometime the linq2sql just makes its mind up about things. I've been pulling my hair for the past hours trying to work out what I'm doing differently from all the other times when I don't get ForeignKeyReferenceAlreadyHasValueException. Turns out that if (this._Activity.HasLoadedOrAssignedValue) { throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException(); } is present on my primary key in this particular table, and in no other. No matter what I do with the association, I've even tried deleting and dragging the thing back to the designer, it's still there and I'm sure it's not supposed to be. I know why, of course, but I don't know why, so to speak. A while back the association went the other way. Whereas I've left that era behind me, the code generator seems to exhibit phantom pains. The same phenomenon, is responsible for me having to change the namespace in the designer.cs everytime I make changes in the designer. I made the mistake of renaming my namespace and the code generator just doesn't get it. Somebody please help this poor boy out.

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