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• how to call include

  - by user276640

  i have 3 tables with such relationship table1-table2-table3 in code i call include("table2"). but how can i call include table3 so i can access to properties of objects table3? if i call include("table3") it show error A specified Include path is not valid

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• LinqToSQL: Not possible to update PrimaryKey?

  - by Zuhaib

  I have a simple table (lets call it Table1) that has a NVARCHAR field as the PK. Table1 has no association with any other tables. When I update Table1's PK column using LinqToSQL it fails. If I update other column it succeeds. I could delete this row and insert new one in Table1, but I don't want to. There is a transaction table which has Table1's PK column as a column. When the PK of Table1 is changed I want no effect in the transaction table. But when the row from Table1 is deleted, I want the transaction rows to be deleted. The cascading is done via Trigger. As there is not association between these two tables, if I update the PK column of Table1 using normal SQL, it works and there is no effect on the transaction table as expected. When I delete the row the trigger deletes the rows from transaction table. For this reason I can't delete and then add new row in Table1. So what can be done to successfully update the PrimaryKey of the Table1?

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• How can I improve the performance of LinqToSql queries that use EntitySet properties?

  - by DanM

  I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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• Error message on using LinqDataSource in webforms

  - by naveen

  Coding Platform: ASP.NET 4.0 I am binding a GridView with LinqDataSource with AutoDelete functionality enabled. GridView is bound to the Products Table. I have a Products Table and a Category Table with an association on CategoryID. If I try to delete a Category that is referred in the Products Table I cannot do that. Its is totally acceptable, but I want the end user to be notified with some error message. Where to catch this error message?

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• How to create view model without sorting collections in memory.

  - by Chevex

  I have a view model (below). public class TopicsViewModel { public Topic Topic { get; set; } public Reply LastReply { get; set; } } I want to populate an IQueryable<TopicsViewModel> with values from my IQueryable<Topic> collection and IQueryable<Reply> collection. I do not want to use the attached entity collection (i.e. Topic.Replies) because I only want the last reply for that topic and doing Topic.Replies.Last() loads the entire entity collection in memory and then grabs the last one in the list. I am trying to stay in IQueryable so that the query is executed in the database. I also don't want to foreach through topics and query replyRepository.Replies because looping through IQueryable<Topic> will start the lazy loading. I'd prefer to build one expression and have all the leg work done in the lower layers. I have the following: IQueryable<TopicsViewModel> topicsViewModel = from x in topicRepository.Topics from y in replyRepository.Replies where y.TopicID == x.TopicID orderby y.PostedDate ascending select new TopicsViewModel { Topic = x, LastReply = y }; But this isn't working. Any ideas how I can populate an IQueryable or IEnumerable of TopicsViewModel so that it queries the database and grabs topics and that topic's last reply? I am trying really hard to avoid grabbing all replies related to that topic. I only want to grab the last reply. Thank you for any insight you have to offer.

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• How to write this query in Linq2Sql

  - by RememberME

  I have a table company which holds the company_id, company_name and other details. I have a table subcontracts which has a company_id column that maps to company.company_id. How can I write a select statement to get all companies which have not been assigned to a subcontract? IE The company_id cannot be found in subcontracts.company_id

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• Do entity collections and object sets implement IQueryable<T>?

  - by Chevex

  I am using Entity Framework for the first time and noticed that the entities object returns entity collections. DBEntities db = new DBEntities(); db.Users; //Users is an ObjectSet<User> User user = db.Users.Where(x => x.Username == "test").First(); //Is this getting executed in the SQL or in memory? user.Posts; //Posts is an EntityCollection<Post> Post post = user.Posts.Where(x => x.PostID == "123").First(); //Is this getting executed in the SQL or in memory? Do both ObjectSet and EntityCollection implement IQueryable? I am hoping they do so that I know the queries are getting executed at the data source and not in memory. EDIT: So apparently EntityCollection does not while ObjectSet does. Does that mean I would be better off using this code? DBEntities db = new DBEntities(); User user = db.Users.Where(x => x.Username == "test").First(); //Is this getting executed in the SQL or in memory? Post post = db.Posts.Where(x => (x.PostID == "123")&&(x.Username == user.Username)).First(); // Querying the object set instead of the entity collection. Also, what is the difference between ObjectSet and EntityCollection? Shouldn't they be the same? Thanks in advance!

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• data is not getting ordered by date

  - by raging_boner

  Can't get list sorted by date. How to show data ordered by date? XDocument doc = XDocument.Load(Server.MapPath("file.xml")); IEnumerable<XElement> items = from item in doc.Descendants("item") orderby Convert.ToDateTime(item.Attribute("lastChanges").Value) descending where item.Attribute("x").Value == 1 select item; Repeater1.DataSource = items; Repeater1.DataBind(); Xml file looks like this: <root> <items> <item id="1" lastChanges="15-05-2010" x="0" /> <item id="2" lastChanges="16-05-2010" x="1" /> <item id="3" lastChanges="17-05-2010" x="1" /> </items> </root>

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• why datetime.now not work when I didn't use tolist?

  - by MemoryLeak

  When I use datacontext.News .Where(p => p.status == true) .Where(p => p.date <= DateTime.Now) .ToList(); the system will return no results; When I use datacontext.News .Where(p => p.status == true) .ToList() .Where(p => p.date <= DateTime.Now) .ToList(); system will return expected results. Can anyone tell me what's up? Thanks in advance !

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• How To Join Tables from Two Different Contexts with LINQ2SQL?

  - by RSolberg

  I have 2 data contexts in my application (different databases) and need to be able to query a table in context A with a right join on a table in context B. How do I go about doing this in LINQ2SQL? Why?: We are using a SaaS product for tracking our time, projects, etc. and would like to send new service requests to this product to prevent our team from duplicating data entry. Context A: This db stores service request information. It is a third party DB and we are not able to make changes to the structure of this DB as it could have unintended non-supportable consequences downstream. Context B: This data stores the "log" data of service requests that have been processed. My team and I have full control over this DB's structure, etc. Unprocessed service requests should find their way into this DB and another process will identify it as not being processed and send the record to the SaaS product. This is the query that I am looking to modify. I was able to do a !list.Contains(c.swHDCaseId) initially, but this cannot handle more than 2100 items. Is there a way to add a join to the other context? var query = (from c in contextA.Cases where monitoredInboxList.Contains(c.INBOXES.inboxName) select new { //setup fields here... });

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• Is an object still connected to a list after FirstOrDefault?

  - by Cynthia

  Here's my code: Event thisEvent = (from i in list where (i.eventID == eventID) select i).FirstOrDefault(); if (thisEvent != null) { thisEvent.eventResolved = resolved; thisEvent.eventSequence.Add(item); } "list" is a collection of IEnumerable, i.e. IEnumerable<Event> list; What I'm wondering is: after creating thisEvent using FirstOrDefault, is thisEvent still connected to list? In other words, when I change the two properties, eventResolved and eventSequence, is "list" actually changed, or is thisEvent just some totally disconnected copy of an item in "list"?

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• How to create Linq2Sql query, calculating aggregates?

  - by pil0t

  Is there any way to create Linq2SQL query, that will be translated to this: SELECT COUNT(*) as totalCount , SUM(v.field1) AS totalfield1, .... SUM(v.<fieldN>) AS total<fieldN> FROM [dbo].[SomeTable] v

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• How to limit select items with L2E/S?

  - by orlon

  This code is a no-go var errors = (from error in db.ELMAH_Error select new { error.Application, error.Host, error.Type, error.Source, error.Message, error.User, error.StatusCode, error.TimeUtc }).ToList(); return View(errors); as it results in a 'requires a model of type IEnumerable' error. The following code of course works fine, but selects all the columns, some of which I'm simply not interested in: var errors = (from error in db.ELMAH_Error select error).ToList(); return View(errors); I'm brand spanking new to MVC2 + L2E, so maybe I'm just not thinking in the right mindset yet, but this seems counter-intuitive. Is there an easy way to select a limited number of columns, or is this just part of using an ORM?

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• Will First() perform the OrderBy()?

  - by Martin

  Is there any difference in (asymptotic) performance between Orders.OrderBy(order => order.Date).First() and Orders.Where(order => order.Date == Orders.Max(x => x.Date)); i.e. will First() perform the OrderBy()? I'm guessing no. MSDN says enumerating the collection via foreach och GetEnumerator does but the phrasing does not exclude other extensions.

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• Entity Framework EntityKey / Foreign Key problem.

  - by Ronny176

  Hi, I keep getting the same error: Entities in 'VlaamseOverheidMeterEntities.ObjectMeter' participate in the 'FK_ObjectMeter_Meter' relationship. 0 related 'Meter' were found. 1 'Meter' is expected. I have the following table structure: Meter 1 <- * ObjectMeter * - 1 VO_Object It is always the same scenario: The first meter is added to the database, the second meter gives the error above. I have the following code in my manager: public List<string> addTemporary(string username, string meterNaam, string readingType, string parentID) { Meter meter = new Meter(); VO_Object voObject = objectManager.getObjectByID(parentID); ObjectMeter objMeter = new ObjectMeter(); meter.readingType = (int)Enum.Parse(typeof(ReadingType), readingType); meter.isActive = true; meter.name = meterNaam; meter.startDate = DateTime.Now; meter.endDate = DateTime.Now.AddYears(6000); meter.uniqueIdentifier = "N/A"; meter.meterType = (int)Enum.Parse(typeof(MeterType), "NA"); meter.meterCategory = (int)Enum.Parse(typeof(MeterCategory), "NA"); meter.energyType = (int)Enum.Parse(typeof(EnergyType), "NA"); meter.utilityType = (int)Enum.Parse(typeof(UtilityType), "NA"); meter.unitOfMeasure = (int)Enum.Parse(typeof(UnitOfMeasure), "NA"); objMeter.valid_from = meter.startDate; objMeter.valid_until = meter.endDate; objMeter.Meter = meter; objMeter.VO_Object = voObject; createMeter(meter); List<String> str = new List<string>(); str.Add("" + meter.meterID); str.Add(meter.name); return str; } and this in my Dao Class which links to the database: internal void CreateMeter(Meter _meter) { _entities.AddToMeter(_meter); _entities.SaveChanges(); } Can someone please explain this error? Ronald

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• Is there a better way to do updates in LinqToSQL?

  - by Vaccano

  I have a list (that comes to my middleware app from the client) that I need to put in my database. Some items in the list may already be in the db (just need an update). Others are new inserts. This turns out to be much harder than I thought I would be. Here is my code to do that. I am hoping there is a better way: public void InsertClients(List<Client> clients) { var comparer = new LambdaComparer<Client>((x, y) => x.Id == y.Id); // Get a listing of all the ones we will be updating var alreadyInDB = ctx.Clients .Where(client => clients.Contains(client, comparer)); // Update the changes for those already in the db foreach (Client clientDB in alreadyInDB) { var clientDBClosure = clientDB; Client clientParam = clients.Find(x => x.Id == clientDBClosure.Id); clientDB.ArrivalTime = clientParam.ArrivalTime; clientDB.ClientId = clientParam.ClientId; clientDB.ClientName = clientParam.ClientName; clientDB.ClientEventTime = clientParam.ClientEventTime; clientDB.EmployeeCount = clientParam.EmployeeCount; clientDB.ManagerId = clientParam.ManagerId; } // Get a list of all clients that are not in my the database. var notInDB = clients.Where(x => alreadyInDB.Contains(x, comparer) == false); ctx.Clients.InsertAllOnSubmit(notInDB); ctx.SubmitChanges(); } This seems like a lot of work to do a simple update. But maybe I am just spoiled. Anyway, if there is a easier way to do this please let me know. Note: If you are curious the code to the LambdaComparer is here: http://gist.github.com/335780#file_lambda_comparer.cs

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• A better solution than element.Elements("Whatever").First()?

  - by codeka

  I have an XML file like this: <SiteConfig> <Sites> <Site Identifier="a" /> <Site Identifier="b" /> <Site Identifier="c" /> </Sites> </SiteConfig> The file is user-editable, so I want to provide reasonable error message in case I can't properly parse it. I could probably write a .xsd for it, but that seems kind of overkill for a simple file. So anyway, when querying for the list of <Site> nodes, there's a couple of ways I could do it: var doc = XDocument.Load(...); var siteNodes = from siteNode in doc.Element("SiteConfig").Element("SiteUrls").Elements("Sites") select siteNode; But the problem with this is that if the user has not included the <SiteUrls> node (say) it'll just throw a NullReferenceException which doesn't really say much to the user about what actually went wrong. Another possibility is just to use Elements() everywhere instead of Element(), but that doesn't always work out when coupled with calls to Attribute(), for example, in the following situation: var siteNodes = from siteNode in doc.Elements("SiteConfig") .Elements("SiteUrls") .Elements("Sites") where siteNode.Attribute("Identifier").Value == "a" select siteNode; (That is, there's no equivalent to Attributes("xxx").Value) Is there something built-in to the framework to handle this situation a little better? What I would prefer is a version of Element() (and of Attribute() while we're at it) that throws a descriptive exception (e.g. "Looking for element <xyz> under <abc> but no such element was found") instead of returning null. I could write my own version of Element() and Attribute() but it just seems to me like this is such a common scenario that I must be missing something...

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• Trigger on database using a web application and a winform application

  - by Michael

  Hello all, Situation: I have a web application which shows errors and where you can accept those error messages. I also have a service, which checks errors from a system and sets the error messages in the database. When I accept an error in the web application, i would like the service to know which error message has been accepted, so that it can do some other actions. My guess is that this could be done through some sort of trigger, but i can't figure out how. Can anyone help me with this?

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• Is it possible to cache all the data in a SQL Server CE database using LinqToSql?

  - by DanM

  I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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• Collection was modified; enumeration operation may not execute

  - by Rita

  I have the below code. I am trying to remove the record and it is throwing Exception when it is removing the Record. "Collection was modified; enumeration operation may not execute." Any ideas on how to get rid of the message. Appreciate your time. //validClaimControlNo has valid ClaimControl Numbers. List<string> validClaimControlNo = new List<string>(); int count = 0; foreach (List<Field> f in records) { foreach (Field fe in f) { if (i == 0) if (!(validClaimControlNo.Contains(fe.Value))) { //if this claim is not in the Valid list, Remove that Record records.RemoveAt(count); } i++; } i = 0; count++; }

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• View Lambdas in Visual Studio Debugger

  - by Vaccano

  I have the a simple LinqToSQL statement that is not working. Something Like this: List<MyClass> myList = _ctx.DBList .Where(x => x.AGuidID == paramID) .Where(x => x.BBoolVal == false) .ToList(); I look at _ctx.DBList in the debugger and the second item fits both parameters. Is there a way I can dig into this more to see what is going wrong?

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• Why is it possible to enumerate a LinqToSql query after calling Dispose() on the DataContext?

  - by DanM

  I'm using the Repository Pattern with some LinqToSql objects. My repository objects all implement IDisposable, and the Dispose() method does only thing--calls Dispose() on the DataContext. Whenever I use a repository, I wrap it in a using person, like this: public IEnumerable<Person> SelectPersons() { using (var repository = _repositorySource.GetNew<Person>(dc => dc.Person)) { return repository.GetAll(); } } This method returns an IEnumerable<Person>, so if my understanding is correct, no querying of the database actually takes place until Enumerable<Person> is traversed (e.g., by converting it to a list or array or by using it in a foreach loop), as in this example: var persons = gateway.SelectPersons(); // Dispose() is fired here var personViewModels = ( from b in persons select new PersonViewModel { Id = b.Id, Name = b.Name, Age = b.Age, OrdersCount = b.Order.Count() }).ToList(); // executes queries In this example, Dispose() gets called immediately after setting persons, which is an IEnumerable<Person>, and that's the only time it gets called. So, a couple questions: How does this work? How can a disposed DataContext still query the database for results when I walk the IEnumerable<Person>? What does Dispose() actually do? I've heard that it is not necessary (e.g., see this question) to dispose of a DataContext, but my impression was that it's not a bad idea. Is there any reason not to dispose of it?

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• how to use Foreign key in L2E or EF when needs insert?

  - by 5YrsLaterDBA

  I know during the retrieve, I can use Include() to load related Entities (http://stackoverflow.com/questions/2632323/how-to-use-foreign-key-in-l2e-or-ef). but when I want to save or insert data, how to handle those reference Entities?

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• For LinqToSQL is 0 true or is 1 (for type Bit)?

  - by Vaccano

  I have a column of type Bit (called BBoolVal in this example). I have a LinqToSQL Statement Like this: var query = List<MyClass> myList = _ctx.DBList .Where(x => x.AGuidID == paramID) .Where(x => x.BBoolVal == false); When I look at the sql it ends up like this (I added the spacing and changed the names): SELECT [t0].[Id], [t0].[AGuidID], [t0].[OtherIDID], [t0].[TimeColumn], [t0].[BBoolVal], [t0].[MoreID] FROM [dbo].[MyTable] AS [t0] WHERE (NOT ([t0].[BBoolVal] = 1)) AND ([t0].[AGuidID] = @p0) Because my x.BBoolVal == false translates to [BBoolVal] == 1 I gather that false = 1 (and thus true = 0). I am asking because this seems a bit backwards to me. I am fine to accept it, I just want to be sure.

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• EF Query with conditional include that uses Joins

  - by makerofthings7

  This is a follow up to another user's question. I have 5 tables CompanyDetail CompanyContacts FK to CompanyDetail CompanyContactsSecurity FK to CompanyContact UserDetail UserGroupMembership FK to UserDetail How do I return all companies and include the contacts in the same query? I would like to include companies that contain zero contacts. Companies have a 1 to many association to Contacts, however not every user is permitted to see every Contact. My goal is to get a list of every Company regardless of the count of Contacts, but include contact data. Right now I have this working query: var userGroupsQueryable = _entities.UserGroupMembership .Where(ug => ug.UserID == UserID) .Select(a => a.GroupMembership); var contactsGroupsQueryable = _entities.CompanyContactsSecurity;//.Where(c => c.CompanyID == companyID); /// OLD Query that shows permitted contacts /// ... I want to "use this query inside "listOfCompany" /// //var permittedContacts= from c in userGroupsQueryable //join p in contactsGroupsQueryable on c equals p.GroupID //select p; However this is inefficient when I need to get all contacts for all companies, since I use a For..Each loop and query each company individually and update my viewmodel. Question: How do I shoehorn the permittedContacts variable above and insert that into this query: var listOfCompany = from company in _entities.CompanyDetail.Include("CompanyContacts").Include("CompanyContactsSecurity") where company.CompanyContacts.Any( // Insert Query here.... // b => b.CompanyContactsSecurity.Join(/*inner*/,/*OuterKey*/,/*innerKey*/,/*ResultSelector*/) ) select company; My attempt at doing this resulted in: var listOfCompany = from company in _entities.CompanyDetail.Include("CompanyContacts").Include("CompanyContactsSecurity") where company.CompanyContacts.Any( // This is concept only... doesn't work... from grps in userGroupsQueryable join p in company.CompanyContactsSecurity on grps equals p.GroupID select p ) select company;

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