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  • JPA - Removing entities

    - by James P.
    I have a Story entity with the following associations: Story <1-* Chapter Story <1-* Comment Story <*-1 User What is the correct way of removing this entity and handling the all the entities that is referring to? Is there some shorthand way of specifying that associated entities must be handled automatically or is the @PreRemove annoation mentionned in the article below a valid of achieving this? http://blog.xebia.com/2009/04/09/jpa-implementation-patterns-removing-entities/

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  • How to tell if any entities in context are dirty with .Net Entity Framework 4.0

    - by Mike Gates
    I want to be able to tell if there is any unsaved data in an entity framework context. I have figured out how to use the ObjectStateManager to check the states of existing entities, but there are two issues I have with this. I would prefer a single function to call to see if any entities are unsaved instead of looping though all entities in the context. I can't figure out how to detect entities I have added. This suggests to me that I do not fully understand how the entity context works. For example, if I have the ObjectSet myContext.Employees, and I add a new employee to this set (with .AddObject), I do not see the new entity when I look at the ObjectSet and I also don't see the .Count increase. However, when I do a context.SaveChanges(), my new entity is persisted...huh? I have been unable to find an answer to this in my msdn searches, so I was hoping someone here would be able to clue me in. Thanks in advance.

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  • How do you implement caching in Linq to SQL?

    - by Glenn Slaven
    We've just started using LINQ to SQL at work for our DAL & we haven't really come up with a standard for out caching model. Previously we had being using a base 'DAL' class that implemented a cache manager property that all our DAL classes inherited from, but now we don't have that. I'm wondering if anyone has come up with a 'standard' approach to caching LINQ to SQL results? We're working in a web environment (IIS) if that makes a difference. I know this may well end up being a subjective question, but I still think the info would be valuable. EDIT: To clarify, I'm not talking about caching an individual result, I'm after more of an architecture solution, as in how do you set up caching so that all your link methods use the same caching architecture.

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  • Is it possible to create ICriteria/ICriterion from LINQ or HQL?

    - by adrin
    I am creating a method that can create filter understood by NHibernate (by filter i mean a set of ICriteria object for example) from my abstract filter object. public static IEnumerable<ICriterion> ToNhCriteria(this MyCriteria criteria) { // T4 generated function // lots of result.Add(Expression.Or(Expression.Eq(),Expression.Eq)) expression trees - hard to generate // Is there a way to generate HQL/Linq query here istead? } then i want to do something like session.CreateCriteria<Entity>().Add(myCriteria.ToNhCriteria()) to filter entities. The problem is that using Expression. methods (Expression.Or etc) is quite tedious (the method is generated and i have multiple or statements that have to be joined into an expression somehow). Is there a way to avoid using Expression.Or() and create ICrietrion / ICriteria using LINQ or HQL?

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  • Quaere - Anyone using it yet? (LINQ to Objects for Java)

    - by Marty Pitt
    Hi there I'm a .NET guy originally, working in Java recently, and finding I'm really missing LINQ to Objects, specifically for performing filtering against collections. A few people here on Stack Overflow have answered the "LINQ for Java?" question with a single word : Quaere However, on the site it clearly states "Pre-Beta", and there's been no commits to their code for over a year, so I'm guessing the project is pretty much dead. Is anyone actually using this, and / or have any experience with it? The second most common answer appears to be "use Google Collections". Is this the most appropriate Java way? Cheers Marty

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  • Update specific rows in LINQ to SQL result set.

    - by davemackey
    I have a page with a form on it and needs a range of dates. Thus I've placed a number of textboxes on the page into which users can type dates. When the user clicks the save button I want to trigger a LINQ update to the SQL Server...all the rows already exist, so I'm just updating existing data. How can I do this? For example, lets say my table looks like this: Column Names: Description dateValue Column Values: Birthdate 1/1/1990 Anniversary 1/10/1992 Death 1/1/1993 I want to do something like this: hupdate.Description("Birthdate").dateValue = TextBox1.Text hupdate.Description("Anniversary").dateValue = TextBox2.Text hupdate.Description("Death").dateValue = TextBox3.Text hconfig.SubmitChanges() Is there a way to do this with LINQ?

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  • .Remove(object) on a List<T> returned from LINQ to SQL compiled query won't delete the Object right

    - by soldieraman
    I am returning two lists from the database using LINQ to SQL compiled query. While looping the first list I remove duplicates from the second list as I dont want to process already existing objects again. eg. //oldCustomers is a List returned by my Compiled Linq to SQL Statmenet that I have added a .ToList() at the end to //Same goes for newCustomers for (Customer oC in oldCustomers) { //Do some processing newCustomers.Remove(newCusomters.Find(nC=> nC.CustomerID == oC.CusomterID)); } for (Cusomter nC in newCustomers) { //Do some processing } DataContext.SubmitChanges() I expect this to only save the changes that have been made to the customers in my processing and not Remove or Delete any of my customers from the database. Correct? I have tried it and it works fine - but I am trying to know if there is any rare case it might actually get removed

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  • How to convert this foreach loop into Linq code?

    - by a-galkin
    I am new one with Linq and I would like to modify my old c# code to use Linq. The idea of this code to select all tables where it's not set and reference’s field PrimaryTable equal "myTable" foreach (Table table in dbServer.Tables) { if (!table.IsSet) { foreach (Reference refer in table.References) { if (refer.PrimaryTable == "myTable") { tables.Add(table); } } } } After digging in internet I have got this code var q = from table in dbServer.Tables let refers = from refer in table.References where refer.PrimaryTable == "myTable" select refer.ForeignTable where refers.Contains(table.Name) select table; But it does not work at all and I need your help to make it works. Thanks in advance.

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  • Best way to get record counts grouped by month, adjusted for time zone, using SQL or LINQ to SQL

    - by Jeff Putz
    I'm looking for the most efficient way to suck out a series of monthly counts of records in my database, but adjusting for time zone, since the times are actually stored as UTC. I would like my result set to be a series of objects that include month, year and count. I have LINQ to SQL objects that looks something like this: public class MyRecord { public int ID { get; set; } public DateTime TimeStamp { get; set; } public string Data { get; set; } } I'm not opposed to using straight SQL, but LINQ to SQL would at least keep the code a lot more clean. The time zone adjustment is available as an integer (-5, for example). Again, the result set what I'm looking for is objects containing the month, year and count, all integers. Any suggestions? I can think of several ways to do it straight, but not with a time zone adjustment.

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  • How to find the maximum value for each key in a List of Dictionaries using LINQ?

    - by Argos
    I have a List of Dictionaries that have keys of type string and values that are ints. Many of the dictionaries have the same keys in them but not all of them. So my question is: using LINQ how would I find the maximum value associated with each distinct key across all of the dictionaries? So for example given the following input: var data = new List<Dictionary<string, int>> { new Dictionary<string, int> {{"alpha", 4}, {"gorilla", 2}, {"gamma", 3}}, new Dictionary<string, int> {{"alpha", 1}, {"beta", 3}, {"gamma", 1}}, new Dictionary<string, int> {{"monkey", 2}, {"beta", 2}, {"gamma", 2}}, }; I would like some kind of collection that contains: {"alpha", 4}, {"gorilla", 2}, {"gamma", 3}, {"beta", 3}, {"monkey", 2} (I'm currently looping through the list and keeping track of things myself, really just wondering if there is a nicer LINQ-esque way of doing it) EDIT: I also don't know what the string keys are in advance

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  • Are entities cached in jpa by default ?

    - by Nitesh Panchal
    Hello, I add entity to my database and it works fine. But when i retrieve the List, i get the old entity, the new entities i add are not shown until i undeploy the application and redeploy it again. This means are my entities cached by default? But, I haven't made any settings for caching entities in my persistence.xml or any such file. I have even tried calling flush(), refresh() and merge(). But still it shows the old entities only. Am i missing something? Please help me.

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  • EF4: common interface for EF entities

    - by Feryt
    Hi. I have public interface: public interface IEntity { int ID { get; set; } string Name { get; set; } bool IsEnabled { get; set; } } ehich some EF entities implements(thanks to partial class) and extesion method: public static IEnumerable<SelectListItem> ToSelectListItems<T>(this IQueryable<T> entities, int? selectedID = null) where T : IEntity { return entities.Select(c => new { c.Name, c.ID }).ToList().Select(c => new SelectListItem { Text = c.Name, Value = c.ID.ToString(), Selected = (c.ID == selectedID) }); } Calling ToSelectListItems return exception: Unable to cast the type '<EF entity name>' to type 'IEntity'. LINQ to Entities only supports casting Entity Data Model primitive types. Why, any ideas? Thank you.

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  • What is the preferred sql server column definition to use for a LINQ to SQL Version property?

    - by Mike Two
    We are using the IsVersion property on the ColumnAttribute on a property in a LINQ to SQL class for optimistic concurrency checks. What should the column definition be in the database? Currently we are using version_number int NOT NULL IDENTITY (1, 1) Do we need Identity? Can we get LINQ to SQL to update the version number for us? The only issue with Identity is that every row has a different number. We'd like to see the number increment by 1 when the row is updated.

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  • How can I evaluate a deferred Linq statement when debugging?

    - by DanO
    I'm debugging in VS2010, and I want to inspect a string value but all I can get the debugger to show me (through watches, hovering, locals, etc.) is: "System.Linq.Enumerable+<TakeIterator>d__3a`1[System.Char]" I don't care if there are side effects from premature evaluation or whatever, I just want to see what the expression would evaluate to if I evaluate it right now at the current breakpoint. How is this done? Also can I change my code in such a way that it evaluates earlier? Not that I care when I'm not debugging... but just wondering. In case it is relevant... (I doubt it.) I'm stuffing a new entity object before saving it to the database... some fields are assigned with LINQ statements, I'm not sure when they get evaluated under the covers of EF. The DB update fails with 'string or binary data would be truncated... So I'm trying to find the too-long field.

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  • Using FileSystemWatcher in detecting a xml file, using Linq in reading the xml file and prompt the results error "Root Element is Missing"

    - by GrayFullBuster
    My application is already working it can detect the xml file and prompt the content of the xml file but sometimes it will prompt "Root element is missing", and sometimes also it is okay but when I open the xml file, it is ok, it has contents on it. How to solve this issue. Here is the screenshot of the error: Here is the code: private void fileSystemWatcher_Created(object sender, System.IO.FileSystemEventArgs e) { string invoice = ""; using (var stream = System.IO.File.Open(e.FullPath, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.ReadWrite)) { var doc = System.Xml.Linq.XDocument.Load(stream); var transac = from r in doc.Descendants("Transaction") select new { InvoiceNumber = r.Element("InvoiceNumber").Value, }; foreach (var i in transac) { invoice = i.InvoiceNumber; } } MessageBox.Show(invoice); fileSystemWatcher.EnableRaisingEvents = false; } The error goes here var doc = System.Xml.Linq.XDocument.Load(stream);

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  • Insert objects into a collection with LINQ based on a property of the existing objects in the collection

    - by DavidS
    Hi, I've got a collection of object which contains data as follows: FromTime Duration 2010-12-28 24.0000 2010-12-29 24.0000 2010-12-30 24.0000 2010-12-31 22.0000 2011-01-02 1.9167 2011-01-03 24.0000 2011-01-04 24.0000 2011-01-05 24.0000 2011-01-06 24.0000 2011-01-07 22.0000 2011-01-09 1.9167 2011-01-10 24.0000 In the "FromTime" column, there are data "gaps" i.e. 2011-01-01 and 2011-01-08 are "missing". So what I'd like to do is to loop through a range of dates (in this instance 2010-12-28 to 2011-01-10) and "fill in" the "missing" data with a duration of 0. As I've just started with LINQ, I feel that it should be "fairly" easy but I can't quite get it right. I'm reading the book "LINQ in Action" but feel that I'm still quite a way off before I can resolve this particular issue. So any help would be much appreciated. David

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  • How do i parse the new wow RSS feed? (LINQ to XML)

    - by Sunzaru Sven
    The link i want to parse is here. I'm looking to parse it in "real time" so that as things happen i can send myself messages/tweets and what not. I plan on having each element of the XML from the feed as an item of a class/struct. I'm really looking for LINQ to XML examples, and a good book. I've seen other LINQ to XML articles out there, but i'm just not grasping how they work. Old SQL minds are hard to break perhaps... /shrug.

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  • How can I avoid setting some columns if others haven't changed, when working with Linq To SQL?

    - by Patrick Szalapski
    In LINQ to SQL, I want to avoid setting some columns if others haven't changed? Say I have dim row = (From c in dataContext.Customers Where c.Id = 1234 Select c).Single() row.Name = "Example" ' line 3 dataContext.SubmitChanges() ' line 4 Great, so LINQ to SQL fetches a row, sets the name to "Example" in memory, and generates an update SQL query only when necessary--that is, no SQL will be generated if the customer's name was already "Example". So suppose on line 3, I want to detect if row has changed, and if so, set row.UpdateDate = DateTime.Now. If row has not changed, I don't want to set row.UpdateDate so that no SQL is generated. Is there any good way to do this?

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  • 'Timeout Expired' error against local SQL Express on only 2 LINQ Methods...

    - by Refracted Paladin
    I am going to sum up my problem first and then offer massive details and what I have already tried. Summary: I have an internal winform app that uses Linq 2 Sql to connect to a local SQL Express database. Each user has there own DB and the DB stay in sync through Merge Replication with a Central DB. All DB's are SQL 2005(sp2or3). We have been using this app for over 5 months now but recently our users are getting a Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Detailed: The strange part is they get that in two differnt locations(2 differnt LINQ Methods) and only the first time they fire in a given time period(~5mins). One LINQ method is pulling all records that match a FK ID and then Manipulating them to form a Heirarchy View for a TreeView. The second is pulling all records that match a FK ID and dumping them into a DataGridView. The only things I can find in common with the 2 are that the first IS an IEnumerable and the second converts itself from IQueryable - IEnumerable - DataTable... I looked at the query's in Profiler and they 'seemed' normal. They are not very complicated querys. They are only pulling back 10 - 90 records, from one table. Any thoughts, suggestions, hints whatever would be greatly appreciated. I am at my wit's end on this.... public IList<CaseNoteTreeItem> GetTreeViewDataAsList(int personID) { var myContext = MatrixDataContext.Create(); var caseNotesTree = from cn in myContext.tblCaseNotes where cn.PersonID == personID orderby cn.ContactDate descending, cn.InsertDate descending select new CaseNoteTreeItem { CaseNoteID = cn.CaseNoteID, NoteContactDate = Convert.ToDateTime(cn.ContactDate). ToShortDateString(), ParentNoteID = cn.ParentNote, InsertUser = cn.InsertUser, ContactDetailsPreview = cn.ContactDetails.Substring(0, 75) }; return caseNotesTree.ToList<CaseNoteTreeItem>(); } AND THIS ONE public static DataTable GetAllCNotes(int personID) { using (var context = MatrixDataContext.Create()) { var caseNotes = from cn in context.tblCaseNotes where cn.PersonID == personID orderby cn.ContactDate select new { cn.ContactDate, cn.ContactDetails, cn.TimeSpentUnits, cn.IsCaseLog, cn.IsPreEnrollment, cn.PresentAtContact, cn.InsertDate, cn.InsertUser, cn.CaseNoteID, cn.ParentNote }; return caseNotes.ToList().CopyLinqToDataTable(); } }

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  • c# How to make linq master detail query for 0..n relationship?

    - by JK
    Given a classic DB structure of Orders has zero or more OrderLines and OrderLine has exactly one Product, how do I write a linq query to express this? The output would be OrderNumber - OrderLine - Product Name Order-1 null null // (this order has no lines) Order-2 1 Red widget I tried this query but is not getting the orders with no lines var model = (from po in Orders from line in po.OrderLines select new { OrderNumber = po.Id, OrderLine = line.LineNumber, ProductName = line.Product.ProductDescription, } ) I think that the 2nd from is limiting the query to only those that have OrderLines, but I dont know another way to express it. LINQ is very non-obvious if you ask me!

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  • iphone coredata removing records between two entities connected by relation ship

    - by satyam
    I'm implementing core data in my iphone app. It has two entities. Entity1: LatestData Entity2: LatestDetailedData LatestData has URL, publishedDate, heading LatestDetailedData has URL, NewsDescription, PublishedDate, Author Both entities have same URL for a record. Both the entities are connected with inverse relation ship. And the relation ship is "delete-Cascaded" What I want: If I remove a record in LatestData, I want the record with same URL in LatestDetailedData must also be deleted. How?

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  • How do I "propagate" my VS2008 Data Sources window with a LINQ query table?

    - by Kent S. Clarkson
    I´m (professionally) creating a SQL Server database client by using Visual Studio 2008, C# - Windows Form(s). And I´m using all the built in stuff, provided by my friend VS Studio, dragging and dropping, creating SQL query tables in DataSet.xsd, and so on... I like that. But! I would like to try out LINQ, as I would like to have something that to me is more intuitive than pure SQL... And (here comes the newbie-problem to be solved)! I don´t know where to put the LINQ code to make a table "pop up" in the Data Sources window - meaning I´m completely stuck! How should I do it?

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