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• Linq to SQL and Realtime Data

  - by Jeremy

  I have an application that needs to constantly (every 50ms), call to an MVC action, and pickup/drop off data. I am using Linq to SQL and MVC because of how simple they are to implement, and I know that they aren't perfect when it comes to performance, but it works relatively well, but the best speed I can get with my current approach is 200ms (without requests overlapping). Each call to the site will create a new instance of the datacontext, query/insert it and return that data. Is there a way to have the datacontext static, but submitchanges say every 5 seconds, so that i am pretty much hitting an in-memory version of the data?

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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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• LINQ 2 SQL Insert Error(with Guids)

  - by Refracted Paladin

  I have the below LINQ method that I use to create the empty EmploymentPLan. After that I simply UPDATE. For some reason this works perfectly for myself but for my users they are getting the following error -- The target table 'dbo.tblEmploymentPrevocServices' of the DML statement cannot have any enabled triggers if the statement contains an OUTPUT clause without INTO clause. This application is a WinForm app that connects to a local SQL 2005 Express database that is a part of a Merge Replication topology. This is an INTERNAL App only installed through ClickOnce. public static Guid InsertEmptyEmploymentPlan(int planID, string user) { using (var context = MatrixDataContext.Create()) { var empPlan = new tblEmploymentQuestionnaire { PlanID = planID, InsertDate = DateTime.Now, InsertUser = user, tblEmploymentJobDevelopmetService = new tblEmploymentJobDevelopmetService(), tblEmploymentPrevocService = new tblEmploymentPrevocService() }; context.tblEmploymentQuestionnaires.InsertOnSubmit(empPlan); context.SubmitChanges(); return empPlan.EmploymentQuestionnaireID; } }

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• How to write back to database from Silverlight?

  - by Manoj

  Hi, I use LINQ to SQL to get data from a database and use a service contract to access it in Silverlight at the client side. I display the data in a DataGrid. Now how do I make sure that any changes in the datagrid is written back to the database? EDIT: This is the example code I implemented: http://www.silverlight.net/learn/tutorials/sqldatagrid-cs/ Here I wanted any change in the datagrid reflected back in the database. The SubmitChanges function works in the DataContext object which is: public partial class DataClasses1DataContext : System.Data.Linq.DataContext But this is not exposed in the contract and so not visible in the client side code.

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• LINQ 2 SQL Insert Error

  - by Refracted Paladin

  I have the below LINQ method that I use to create the empty EmploymentPLan. After that I simply UPDATE. For some reason this works perfectly for myself but for my users they are getting the following error -- The target table 'dbo.tblEmploymentPrevocServices' of the DML statement cannot have any enabled triggers if the statement contains an OUTPUT clause without INTO clause. This application is a WinForm app that connects to a local SQL 2005 Express database. public static Guid InsertEmptyEmploymentPlan(int planID, string user) { using (var context = MatrixDataContext.Create()) { var empPlan = new tblEmploymentQuestionnaire { PlanID = planID, InsertDate = DateTime.Now, InsertUser = user, tblEmploymentJobDevelopmetService = new tblEmploymentJobDevelopmetService(), tblEmploymentPrevocService = new tblEmploymentPrevocService() }; context.tblEmploymentQuestionnaires.InsertOnSubmit(empPlan); context.SubmitChanges(); return empPlan.EmploymentQuestionnaireID; } }

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• When does the DataContext will open a connection to the DB?

  - by Eran Betzalel

  I am using L2S to access my MSSQL 2008 Express server. I would like to know when the DataContext will open a connection to the DB? and will it close the connection right after it opened it? For example: var dc = new TestDB(); // connection opened and closed? dc.SomeTable.InsertOnSubmit(obj); // connection opened and closed? foreach(var obj in dc.SomeTable.AsEnumerable()) // connection opened and closed? { ... // connection opened and closed? } dc.SubmitChanges(); // connection opened and closed?

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• Use LINQ to insert data from dataset to SQL

  - by Mayo

  Let's say I have a dataset in an ASP.NET website (.NET 3.5) with 5 tables, each has roughly 30,000 rows and an average of 12 columns. I want to insert all of the data from the dataset into 5 very-similar-but-not-quite-identical tables in SQL Server 2008. I also want to use LINQ (personal preference - trying to learn something new). Is it as simple as iterating through the dataset and, for each row, creating a new instance of the associated class, initializing its data with the dataset's row, adding it to the data model, and then doing one giant SubmitChanges at the end? Are there better ways of doing this with LINQ? Or is this the de-facto standard?

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• C# LINQ join With Just One Row

  - by Soo

  I'm trying to make a query that grabs a single row from an SQL database and updates it. TableA AId AValue TableB BId AId BValue Ok, so TableA and TableB are linked by AId. I want to select a row in TableB based on AValue using a join. The following query is what I have and only grabs a value from TableB based on AId, I just don't know how to grab a row from TableB using AValue. I know you would need to use a join, but I'm not sure how to accomplish that. var row = DbObject.TableB.Single(x => x.AId == 1) row.BValue = 1; DbObject.SubmitChanges();

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• Mapping LINQ to SQL table to another very similar table without iterating through every one

  - by Daniel Coffman

  Apologies for the vague question. Here it is: I have a table object created by LINQ to SQL. I am copying entries from one table to an "archive" table that has all the columns of the original, plus a couple extra ones. It feels sloppy to iterate through every object and manually define the mapping like: foreach (oldTable in dbContextOldTables) { var newTable = new NewTable(); newTable.TableID = oldTable.ID; newTable.Title = oldTable.Title; ... (repeat for twenty columns) newTable.ColumnThatIsntInOldTable = "Data that will be the same for every row"; dbContext.NewTables.InsertOnSubmit(newTable); } dbContext.SubmitChanges(); Is there a clever way to do this?

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• Next Identity Key LINQ + SQL Server

  - by user569347

  To represent our course tree structure in our Linq Dataclasses we have 2 columns that could potentially be the same as the PK. My problem is that if I want to Insert a new record and populate 2 other columns with the PK that was generated there is no way I can get the next identity and stop conflict with other administrators who might be doing the same insert at the same time. Case: A Leaf node has right_id and left_id = itself (prereq_id) **dbo.pre_req:** prereq_id left_id right_id op_id course_id is_head is_coreq is_enforced parent_course_id and I basically want to do this: pre_req rec = new pre_req { left_id = prereq_id, right_id = prereq_id, op_id = 3, course_id = query.course_id, is_head = true, is_coreq = false, parent_course_id = curCourse.course_id }; db.courses.InsertOnSubmit(rec); try { db.SubmitChanges(); } Any way to solve my dilemma? Thanks!

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• Linq To SQL: Behaviour for table field which is NotNull and having Default value or binding

  - by kaushalparik27

  I found this something interesting while wandering over community which I would like to share. The post is whole about: DBML is not considering the table field's "Default value or Binding" setting which is a NotNull. I mean the field which can not be null but having default value set needs to be set IsDbGenerated = true in DBML file explicitly.Consider this situation: There is a simple tblEmployee table with below structure: The fields are simple. EmployeeID is a Primary Key with Identity Specification = True with Identity Seed = 1 to autogenerate numeric value for this field. EmployeeName and their EmailAddress to store in rest of 2 fields. And the last one is "DateAdded" with DateTime datatype which doesn't allow NULL but having Default Value/Binding with "GetDate()". That means if we don't pass any value to this field then SQL will insert current date in "DateAdded" field.So, I start with a new website, add a DBML file and dropped the said table to generate LINQ To SQL context class. Finally, I write a simple code snippet to insert data into the tblEmployee table; BUT, I am not passing any value to "DateAdded" field. Because I am considering SQL Server's "Default Value or Binding (GetDate())" setting to this field and understand that SQL will insert current date to this field.        using (TestDatabaseDataContext context = new TestDatabaseDataContext())        {            tblEmployee tblEmpObjet = new tblEmployee();            tblEmpObjet.EmployeeName = "KaushaL";            tblEmpObjet.EmployeeEmailAddress = "[email protected]";            context.tblEmployees.InsertOnSubmit(tblEmpObjet);            context.SubmitChanges();        }Here comes the twist when application give me below error:  This is something not expecting! From the error it clearly depicts that LINQ is passing NULL value to "DateAdded" Field while according to my understanding it should respect Sql Server's "Default value or Binding" setting for this field. A bit googling and I found very interesting related to this problem.When we set Primary Key to any field with "Identity Specification" Property set to true; DBML set one important property "IsDbGenerated=true" for this field. BUT, when we set "Default Value or Biding" property for some field; we need to explicitly tell the DBML/LINQ to let it know that this field is having default binding at DB side that needs to be respected if I don't pass any value. So, the solution is: You need to explicitly set "IsDbGenerated=true" for such field to tell the LINQ that the field is having default value or binding at Sql Server side so, please don't worry if i don't pass any value for it.You can select the field and set this property from property window in DBML Designer file or write the property in DBML.Designer.cs file directly. I have attached a working example with required table script with this post here. I hope this would be helpful for someone hunting for the same. Happy Discovery!

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• Telerik RADGrid - linq and updating

  - by Dave

  Hi Telerik's RADGrid, basing on their example on http://demos.telerik.com/aspnet-ajax/grid/examples/dataediting/programaticlinqupdates/defaultcs.aspx Problem: I can insert and delete, however updating doesn't work. No error trapped. Data just doesn't change. From the code below it looks like Telerik Grid is doing some kung-fu behind the scenes to wire things up. I can't see the db receiving any update statements. Question: anything obvious I'm missing? protected void RadGrid1_UpdateCommand(object source, GridCommandEventArgs e) { var editableItem = ((GridEditableItem) e.Item); var raceId = (Guid) editableItem.GetDataKeyValue("RaceID"); //retrive entity form the Db var race = DbContext.races.Where(n => n.raceid == raceId).FirstOrDefault(); if (race != null) { //update entity's state editableItem.UpdateValues(race); try { //submit chanages to Db DbContext.SubmitChanges(); } catch (Exception f) { ShowErrorMessage(f); } } } Think I may have to go back to their example.. get their db.. and attack from that point of view. Cheers!

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• Linq to SQL and concurrency with Rob Conery repository pattern

  - by David Hall

  I have implemented a DAL using Rob Conery's spin on the repository pattern (from the MVC Storefront project) where I map database objects to domain objects using Linq and use Linq to SQL to actually get the data. This is all working wonderfully giving me the full control over the shape of my domain objects that I want, but I have hit a problem with concurrency that I thought I'd ask about here. I have concurrency working but the solution feels like it might be wrong (just one of those gitchy feelings). The basic pattern is: private MyDataContext _datacontext private Table _tasks; public Repository(MyDataContext datacontext) { _dataContext = datacontext; } public void GetTasks() { _tasks = from t in _dataContext.Tasks; return from t in _tasks select new Domain.Task { Name = t.Name, Id = t.TaskId, Description = t.Description }; } public void SaveTask(Domain.Task task) { Task dbTask = null; // Logic for new tasks omitted... dbTask = (from t in _tasks where t.TaskId == task.Id select t).SingleOrDefault(); dbTask.Description = task.Description, dbTask.Name = task.Name, _dataContext.SubmitChanges(); } So with that implementation I've lost concurrency tracking because of the mapping to the domain task. I get it back by storing the private Table which is my datacontext list of tasks at the time of getting the original task. I then update the tasks from this stored Table and save what I've updated This is working - I get change conflict exceptions raised when there are concurrency violations, just as I want. However, it just screams to me that I've missed a trick. Is there a better way of doing this? I've looked at the .Attach method on the datacontext but that appears to require storing the original version in a similar way to what I'm already doing. I also know that I could avoid all this by doing away with the domain objects and letting the Linq to SQL generated objects all the way up my stack - but I dislike that just as much as I dislike the way I'm handling concurrency.

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• LINQ To SQL ignore unique constraint exception and continue

  - by Martin

  I have a single table in a database called Users Users ------ ID (PK, Identity) Username (Unique Index) I have setup a unique index on the Username table to prevent duplicates. I am then enumerating through a collection and creating a new user in the database for each item. What I want to do is just insert a new user and ignore the exception if the unique key constraint is violated (as it's clearly a duplicate record in that case). This is to avoid having to craft where not exists kind of queries. First off, is this going to be any more efficient or should my insert code be checking for duplicates instead? I'm drawn more to the database having that logic as this prevents any other type of client from inserting duplicate data. My other issue is related to LINQ To SQL. I have the following code: public class TestRepo { DatabaseDataContext database = new DatabaseDataContext(); public void Add(string username) { database.Users.InsertOnSubmit(new User() { Username = username }); } public void Save() { database.SubmitChanges(); } } And then I iterate over a collection and insert new users, ignoring any exceptions: TestRepo repo = new TestRepo(); foreach (var name in new string[] { "Tim", "Bob", "John" }) { try { repo.Add(name); repo.Save(); } catch { } } The first time this is run, great I have three users in the table. If I remove the second one and run this code again, nothing is inserted. I expected the first insert to fail with the exception, the second to succeed (as I just removed that item from the DB) and the third to then fail. What seems to be happening is that once the SqlException is thrown (even though the loop continues to iterate) all of the next inserts fail - even when there isn't a row in the table that would cause a unique violation. Can anyone explain this? P.S. The only workaround I could find was to instantiate the repo each time before the insert, then it worked exactly as excepted - indicating that it's something to do with the LINQ To SQL DataContext. Thanks.

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• Validate MVC 2 form using Data annotations and Linq-to-SQL, before the model binder kicks in (with D

  - by Stefanvds

  I'm using linq to SQL and MVC2 with data annotations and I'm having some problems on validation of some types. For example: [DisplayName("Geplande sessies")] [PositiefGeheelGetal(ErrorMessage = "Ongeldige ingave. Positief geheel getal verwacht")] public string Proj_GeplandeSessies { get; set; } This is an integer, and I'm validating to get a positive number from the form. public class PositiefGeheelGetalAttribute : RegularExpressionAttribute { public PositiefGeheelGetalAttribute() : base(@"\d{1,7}") { } } Now the problem is that when I write text in the input, I don't get to see THIS error, but I get the errormessage from the modelbinder saying "The value 'Tomorrow' is not valid for Geplande sessies." The code in the controller: [HttpPost] public ActionResult Create(Projecten p) { if (ModelState.IsValid) { _db.Projectens.InsertOnSubmit(p); _db.SubmitChanges(); return RedirectToAction("Index"); } else { SelectList s = new SelectList(_db.Verbonds, "Verb_ID", "Verb_Naam"); ViewData["Verbonden"] = s; } return View(); } What I want is being able to run the Data Annotations before the Model binder, but that sounds pretty much impossible. What I really want is that my self-written error messages show up on the screen. I have the same problem with a DateTime, which i want the users to write in the specific form 'dd/MM/yyyy' and i have a regex for that. but again, by the time the data-annotations do their job, all i get is a DateTime Object, and not the original string. So if the input is not a date, the regex does not even run, cos the data annotations just get a null, cos the model binder couldn't make it to a DateTime. Does anyone have an idea how to make this work?

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• Membership.GetUser() within TransactionScope throws TransactionPromotionException

  - by Bob Kaufman

  The following code throws a TransactionAbortedException with message "The transaction has aborted" and an inner TransactionPromotionException with message "Failure while attempting to promote transaction": using ( TransactionScope transactionScope = new TransactionScope() ) { try { using ( MyDataContext context = new MyDataContext() ) { Guid accountID = new Guid( Request.QueryString[ "aid" ] ); Account account = ( from a in context.Accounts where a.UniqueID.Equals( accountID ) select a ).SingleOrDefault(); IQueryable < My_Data_Access_Layer.Login > loginList = from l in context.Logins where l.AccountID == account.AccountID select l; foreach ( My_Data_Access_Layer.Login login in loginList ) { MembershipUser membershipUser = Membership.GetUser( login.UniqueID ); } [... lots of DeleteAllOnSubmit() calls] context.SubmitChanges(); transactionScope.Complete(); } } catch ( Exception E ) { [... reports the exception ...] } } The error occurs at the call to Membership.GetUser(). My Connection String is: <add name="MyConnectionString" connectionString="Data Source=localhost\SQLEXPRESS;Initial Catalog=MyDatabase;Integrated Security=True" providerName="System.Data.SqlClient" /> Everything I've read tells me that TransactionScope should just get magically applied to the Membership calls. The user exists (I'd expect a null return otherwise.)

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• Error when creating a new entity foo, editing a previously existing foo, then saving. Generic 4004 e

  - by Tarks

  The steps are as simple as that so I imagine there's something else going on here, the problem is I just get back 4004, no exception anywhere etc, making it annoying to debug, I get this from the ie error window Microsoft JScript runtime error: Unhandled Error in Silverlight Application Code: 4004 Category: ManagedRuntimeError Message: System.Windows.Ria.DomainOperationException: Submit operation failed. An error occurred while updating the entries. See the inner exception for details. at System.Windows.Ria.OperationBase.Complete(Exception error) at System.Windows.Ria.SubmitOperation.Complete(Exception error) at System.Windows.Ria.DomainContext.CompleteSubmitChanges(IAsyncResult asyncResult) at System.Windows.Ria.DomainContext.<c_DisplayClassd.b_5(Object ) public void TurnPage(bool forward) { TurnPageForward = forward; // If the pages are already turning then don't try and skip days, just run the animation function so it inreases the speed if (!workBook.IsTransitioning && !IsWaitingForData) { IsWaitingForData = true; workBook.SnapshotPages(); NoteCtx.SubmitChanges().Completed += (s, a) => { workBook.ClearPageContents(); CurrentDate = CurrentDate.AddDays(forward ? 1 : -1); PullNotes(CurrentDate); }; } else { workBook.BeginTurnPages(TurnPageForward); } } public void PullNotes(DateTime? noteTime) { NoteCtx.NoteItems.Clear(); var loadOp = NoteCtx.Load(NoteCtx.GetNoteItemsForDayQuery(CurrentDate)); loadOp.Completed += new EventHandler(NotesReady); }

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• Subsonic 3.0.0.4 Does not Update

  - by geocine

  I tried 3 variants but doesn't seem to update (I am using Linq Templates and MSSQL) Luna.Data.GameDBDB db = new Luna.Data.GameDBDB(); db.Update<Luna.Record.TB_ITEM>() .Set(x => x.ITEM_DURABILITY == Convert.ToInt32(quantity)) .Where(x => x.ITEM_DBIDX == Convert.ToInt32(dbdidx)) .Execute(); Here is the other one var db = new Luna.Data.GameDBDB(); var query = (from p in db.TB_ITEMS where p.ITEM_DBIDX == Convert.ToInt32(dbidx) select p).Single(); query.ITEM_DURABILITY = Convert.ToInt32(quantity); db.tp TP_ITEM_UPDATE(); and the other one var db = new Luna.Data.GameDBDB(); var query = (from p in db.TB_ITEMS where p.ITEM_DBIDX == Convert.ToInt32(dbidx) select p).Single(); query.ITEM_DURABILITY = Convert.ToInt32(quantity); db.Update<Luna.Data.TB_ITEM>(); However it worked using LINQ-to-SQL LunaDataContext db = new LunaDataContext(); var query = (from p in db.TB_ITEMs where p.ITEM_DBIDX == Convert.ToInt32(dbidx) select p).Single(); query.ITEM_DURABILITY = Convert.ToInt32(quantity); db.SubmitChanges(); Is this a bug in 3.0.0.4, the database record couldn't be updated using Linq Templates and ActiveRecord.

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• How can I write a clean Repository without exposing IQueryable to the rest of my application?

  - by Simucal

  So, I've read all the Q&A's here on SO regarding the subject of whether or not to expose IQueryable to the rest of your project or not (see here, and here), and I've ultimately decided that I don't want to expose IQueryable to anything but my Model. Because IQueryable is tied to certain persistence implementations I don't like the idea of locking myself into this. Similarly, I'm not sure how good I feel about classes further down the call chain modifying the actual query that aren't in the repository. So, does anyone have any suggestions for how to write a clean and concise Repository without doing this? One problem I see, is my Repository will blow up from a ton of methods for various things I need to filter my query off of. Having a bunch of: IEnumerable GetProductsSinceDate(DateTime date); IEnumberable GetProductsByName(string name); IEnumberable GetProductsByID(int ID); If I was allowing IQueryable to be passed around I could easily have a generic repository that looked like: public interface IRepository<T> where T : class { T GetById(int id); IQueryable<T> GetAll(); void InsertOnSubmit(T entity); void DeleteOnSubmit(T entity); void SubmitChanges(); } However, if you aren't using IQueryable then methods like GetAll() aren't really practical since lazy evaluation won't be taking place down the line. I don't want to return 10,000 records only to use 10 of them later. What is the answer here? In Conery's MVC Storefront he created another layer called the "Service" layer which received IQueryable results from the respository and was responsible for applying various filters. Is this what I should do, or something similar? Have my repository return IQueryable but restrict access to it by hiding it behind a bunch of filter classes like GetProductByName, which will return a concrete type like IList or IEnumerable?

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• LINQ(2 SQL) Insert Multiple Tables Question

  - by Refracted Paladin

  I have 3 tables. A primary EmploymentPlan table with PK GUID EmploymentPlanID and 2 FK's GUID PrevocServicesID & GUID JobDevelopmentServicesID. There are of course other fields, almost exclusively varchar(). Then the 2 secondary tables with the corresponding PK to the primary's FK's. I am trying to write the LINQ INSERT Method and am struggling with the creation of the keys. Say I have a method like below. Is that correct? Will that even work? Should I have seperate methods for each? Also, when INSERTING I didn't think I needed to provide the PK for a table. It is auto-generated, no? Thanks, public static void InsertEmploymentPlan(int planID, Guid employmentQuestionnaireID, string user, bool communityJob, bool jobDevelopmentServices, bool prevocServices, bool transitionedPrevocIntegrated, bool empServiceMatchPref) { using (var context = MatrixDataContext.Create()) { var empPrevocID = Guid.NewGuid(); var prevocPlan = new tblEmploymentPrevocService { EmploymentPrevocID = empPrevocID }; context.tblEmploymentPrevocServices.InsertOnSubmit(prevocPlan); var empJobDevID = Guid.NewGuid(); var jobDevPlan = new tblEmploymentJobDevelopmetService() { JobDevelopmentServicesID = empJobDevID }; context.tblEmploymentJobDevelopmetServices.InsertOnSubmit(jobDevPlan); var empPlan = new tblEmploymentQuestionnaire { CommunityJob = communityJob, EmploymentQuestionnaireID = Guid.NewGuid(), InsertDate = DateTime.Now, InsertUser = user, JobDevelopmentServices = jobDevelopmentServices, JobDevelopmentServicesID =empJobDevID, PrevocServices = prevocServices, PrevocServicesID =empPrevocID, TransitionedPrevocToIntegrated =transitionedPrevocIntegrated, EmploymentServiceMatchPref = empServiceMatchPref }; context.tblEmploymentQuestionnaires.InsertOnSubmit(empPlan); context.SubmitChanges(); } } I understand I can use more then 1 InsertOnSubmit, See SO ? HERE, I just don't understand how that would apply to my situation and the PK/FK creation.

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• Linq to SQL not inserting data onto the DB

  - by Jesus Rodriguez

  Hello! I have a little / weird behaviour here and Im looking over internet and SO and I didn't find a response. I have to admit that this is my first time using databases, I know how to use them with SQL but never used it actually. Anyway, I have a problem with my app inserting data, I just created a very simple project for testing that and no solution yet. I have an example database with Sql Server Id - int (identity primary key) Name - nchar(10) (not null) The table is called "Person", simple as pie. I have this: static void Main(string[] args) { var db = new ExampleDBDataContext {Log = Console.Out}; var jesus = new Person {Name = "Jesus"}; db.Persons.InsertOnSubmit(jesus); db.SubmitChanges(); var query = from person in db.Persons select person; foreach (var p in query) { Console.WriteLine(p.Name); } } As you can see, nothing extrange. It show Jesus in the console. But if you see the table data, there is no data, just empty. I comment the object creation and insertion and the foreach doesn't print a thing (normal, there is no data in the database) The weird thing is that I created a row in the database manually and the Id was 2 and no 1 (Was the linq really playing with the database but it didn't create the row?) There is the log: INSERT INTO [dbo].Person VALUES (@p0) SELECT CONVERT(Int,SCOPE_IDENTITY()) AS [value] -- @p0: Input NChar (Size = 10; Prec = 0; Scale = 0) [Jesus] -- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.30729.4926 SELECT [t0].[Id], [t0].[Name] FROM [dbo].[Person] AS [t0] -- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.30729.4926 I am really confused, All the blogs / books use this kind of snippet to insert an element to a database. Thank you for helping.

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• The ViewData item that has the key 'MY KEY' is of type 'System.String' but must be of type 'IEnumerable<SelectListItem>'.

  - by JBibbs

  I am trying to populate a dropdown list from a database mapped with Linq 2 SQL, using ASP.NET MVC 2, and keep getting this error. I am so confused because I am declaring a variable with the type IEnumerable<SelectListItem> on the second line, but the error makes me think this is not the case. I feel like this should be very simple, but I am struggling. Any help is appreciated. Here are the interesting bits of my controller: public ActionResult Create() { var db = new DB(); IEnumerable<SelectListItem> basetypes = db.Basetypes.Select(b => new SelectListItem { Value = b.basetype, Text = b.basetype }); ViewData["basetype"] = basetypes; return View(); } And here are the interesting bits of my view: <div class="editor-label"> <%: Html.LabelFor(model => model.basetype) %> </div> <div class="editor-field"> <%: Html.DropDownList("basetype") %> <%: Html.ValidationMessageFor(model => model.basetype) %> </div> Here is the Post action when submitting the Form // POST: /Meals/Create [HttpPost] public ActionResult Create(Meal meal) { if (ModelState.IsValid) { try { // TODO: Add insert logic here var db = new DB(); db.Meals.InsertOnSubmit(meal); db.SubmitChanges(); return RedirectToAction("Index"); } catch { return View(meal); } } else { return View(meal); } } Thanks.

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• Can this be considered Clean Code / Best Practice?

  - by MRFerocius

  Guys, How are you doing today? I have the following question because I will follow this strategy for all my helpers (to deal with the DB entities) Is this considered a good practice or is it going to be unmaintainable later? public class HelperArea : AbstractHelper { event OperationPerformed<Area> OnAreaInserting; event OperationPerformed<Area> OnAreaInserted; event OperationPerformed<Area> OnExceptionOccured; public void Insert(Area element) { try { if (OnAreaInserting != null) OnAreaInserting(element); DBase.Context.Areas.InsertOnSubmit(new AtlasWFM_Mapping.Mapping.Area { areaDescripcion = element.Description, areaNegocioID = element.BusinessID, areaGUID = Guid.NewGuid(), areaEstado = element.Status, }); DBase.Context.SubmitChanges(); if (OnAreaInserted != null) OnAreaInserted(element); } catch (Exception ex) { LogManager.ChangeStrategy(LogginStrategies.EVENT_VIEWER); LogManager.LogError(new LogInformation { logErrorType = ErrorType.CRITICAL, logException = ex, logMensaje = "Error inserting Area" }); if (OnExceptionOccured != null) OnExceptionOccured(elemento); } } I want to know if it is a good way to handle the event on the Exception to let subscribers know that there has been an exception inserting that Area. And the way to log the Exception, is is OK to do it this way? Any suggestion to make it better?

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• LINQ to SQL - Tracking New / Dirty Objects

  - by Joseph Sturtevant

  Is there a way to determine if a LINQ object has not yet been inserted in the database (new) or has been changed since the last update (dirty)? I plan on binding my UI to LINQ objects (using WPF) and need it to behave differently depending whether or not the object is already in the database. MyDataContext context = new MyDataContext(); MyObject obj; if (new Random().NextDouble() > .5) obj = new MyObject(); else obj = context.MyObjects.First(); // How can I distinguish these two cases? The only simple solution I can think of is to set the primary key of new records to a negative value (my PKs are an identity field and will therefore be set to a positive integer on INSERT). This will only work for detecting new records. It also requires identity PKs, and requires control of the code creating the new object. Is there a better way to do this? It seems like LINQ must be internally tracking the status of these objects so that it can know what to do on context.SubmitChanges(). Is there some way to access that "object status"? Clarification Apparently my initial question was confusing. I'm not looking for a way to insert or update records. I'm looking for a way, given any LINQ object, to determine if that object has not been inserted (new) or has been changed since its last update (dirty).

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• InsertOnSubmit - NullReferenceException

  - by Jackie Chou

  I have 2 Model AccountEntity [Table(Name = "Account")] public class AccountEntity { [Column(IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)] public int id { get; set; } [Column(CanBeNull = false, Name = "email")] public string email { get; set; } [Column(CanBeNull = false, Name = "pwd")] public string pwd { get; set; } [Column(CanBeNull = false, Name = "row_guid")] public Guid guid { get; set; } private EntitySet<DetailsEntity> details_id { get; set; } [Association(Storage = "details_id", OtherKey = "id", ThisKey = "id")] public ICollection<DetailsEntity> detailsCollection { get; set; } } DetailsEntity [Table(Name = "Details")] public class DetailsEntity { public DetailsEntity(AccountEntity a) { this.Account = a; } [Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "int")] public int id { get; set; } private EntityRef<AccountEntity> _account = new EntityRef<AccountEntity>(); [Association(IsForeignKey = true, Storage = "_account", ThisKey = "id")] public AccountEntity Account { get; set; } } Main using (Database db = new Database()) { AccountEntity a = new AccountEntity(); a.email = "hahaha"; a.pwd = "13212312"; a.guid = Guid.NewGuid(); db.Account.InsertOnSubmit(a); db.SubmitChanges(); } that has relationhip AccountEntity <- DetailsEntity (1-n) when i'm trying to insert a record exception throws NullReferenceException cause: by EntitySet null please help me make it insert

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