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  • Expand in linq not loading inner data collections from service.

    - by Kit
    I am seeing odd behavior with service queries! I am using MVVM pattern for a silverlight 3 app on 3.5 framework and Dataservices 1.5. The following code eager loads correctly the parent object and the child heirarchy perfectly IF and ONLY IF I am preloading the data. But I would like to fetch a different set of the parent object (and its child heirarchy) on different button clicks. What I am seeing is that on button click, only the parent object is retrieved, and the child heirarchy contains nothing. Any suggestions? Any ideas how to tackle this? Thanks all. The method: DataServiceQuery serviceQuery = (DataServiceQuery)(from m1 in dbEntities.gis_Region.Expand("gis_RegionValue/gis_Measure") where m1.RegionGuid == new Guid(regionGuid) select m1); serviceQuery.BeginExecute(GetRegionDetailAsyncResult, serviceQuery); The wired Async Result: DataServiceQuery query = (DataServiceQuery)result.AsyncState; gis_Region region = query.EndExecute(result).First();

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  • How can I implement NotOfType<T> in LINQ that has a nice calling syntax?

    - by Lette
    I'm trying to come up with an implementation for NotOfType, which has a readable call syntax. NotOfType should be the complement to OfType<T> and would consequently yield all elements that are not of type T My goal was to implement a method which would be called just like OfType<T>, like in the last line of this snippet: public abstract class Animal {} public class Monkey : Animal {} public class Giraffe : Animal {} public class Lion : Animal {} var monkey = new Monkey(); var giraffe = new Giraffe(); var lion = new Lion(); IEnumerable<Animal> animals = new Animal[] { monkey, giraffe, lion }; IEnumerable<Animal> fewerAnimals = animals.NotOfType<Giraffe>(); However, I can not come up with an implementation that supports that specific calling syntax. This is what I've tried so far: public static class EnumerableExtensions { public static IEnumerable<T> NotOfType<T>(this IEnumerable<T> sequence, Type type) { return sequence.Where(x => x.GetType() != type); } public static IEnumerable<T> NotOfType<T, TExclude>(this IEnumerable<T> sequence) { return sequence.Where(x => !(x is TExclude)); } } Calling these methods would look like this: // Animal is inferred IEnumerable<Animal> fewerAnimals = animals.NotOfType(typeof(Giraffe)); and // Not all types could be inferred, so I have to state all types explicitly IEnumerable<Animal> fewerAnimals = animals.NotOfType<Animal, Giraffe>(); I think that there are major drawbacks with the style of both of these calls. The first one suffers from a redundant "of type/type of" construct, and the second one just doesn't make sense (do I want a list of animals that are neither Animals nor Giraffes?). So, is there a way to accomplish what I want? If not, could it be possible in future versions of the language? (I'm thinking that maybe one day we will have named type arguments, or that we only need to explicitly supply type arguments that can't be inferred?) Or am I just being silly?

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  • Differences between query using LINQ and IQueryable interface directly?

    - by JohnMetta
    Using Entity Framework 4, and given: ObjectSet<Thing> AllThings = Context.CreateObjectSet<Thing>; public IQueryable<Thing> ByNameA(String name) { IQueryable<Thing> query = from o in AllThings where o.Name == name select o; return query; } public IQueryable<Thing> ByNameB(String name) { return AllThings.Where((o) => o.Name == name); } Both return IQueryable< instances, and thus the query doesn't hit the server until something like ToList() is called, right? Is it purely readability that is the difference, or are the using fundamentally different technologies on the back-end?

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  • Is there a better way to write this LINQ query?

    - by Raj Aththanayake
    Hi Is there a better simplified way to write this query. My logic is if collection contains customer ids and countrycodes, do the query ordey by customer id ascending. If there are no contain id in CustIDs then do the order by customer name. Is there a better way to write this query? I'm not really familiar with complex lambdas. var custIdResult = (from Customer c in CustomerCollection where (c.CustomerID.ToLower().Contains(param.ToLower()) && (countryCodeFilters.Any(item => item.Equals(c.CountryCode))) ) select c).ToList(); if (custIdResult.Count > 0) { return from Customer c in custIdResult where ( c.CustomerName.ToLower().Contains(param.ToLower()) && countryCodeFilters.Any(item => item.Equals(c.CountryCode))) orderby c.CustomerID ascending select c; } else { return from Customer c in CustomerCollection where (c.CustomerName.ToLower().Contains(param.ToLower()) && countryCodeFilters.Any(item => item.Equals(c.CountryCode))) orderby c.CustomerName descending select c; }

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  • Filter a list of objects using a property that is another list. Usign linq.

    - by Luís Custódio
    I've a nice situation, I think at beginning this a usual query but I'm having some problem trying to solve this, the situation is: I've a list of "Houses", and each house have a list of "Windows". And I want to filter for a catalog only the Houses witch have a Blue windows, so my extension method of House is something like: public static List<House> FilterByWindow (this IEnumerable<House> houses, Window blueOne){ houses.Select(p=>p.Windows.Where(q=>q.Color == blueOne.Color)); return houses.ToList(); } Is this correct or I'm losing something? Some better suggestion?

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  • What is difference between Where and Join in linq ?

    - by Freshblood
    hello What is difference between of these 2 queries ? they are completely equal ? from order in myDB.OrdersSet from person in myDB.PersonSet from product in myDB.ProductSet where order.Persons_Id==person.Id && order.Products_Id==product.Id select new { order.Id, person.Name, person.SurName, product.Model,UrunAdi=product.Name }; and from order in myDB.OrdersSet join person in myDB.PersonSet on order.Persons_Id equals person.Id join product in myDB.ProductSet on order.Products_Id equals product.Id select new { order.Id, person.Name, person.SurName, product.Model,UrunAdi=product.Name };

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  • Attach an entity that is not new, perhaps having been loaded from another DataContext. LINQ to SQL -

    - by soldieraman
    Alright How I got this error I got one application sitting on a server 2 users accessing this application - doing some bulk data processing . eg. entering values and then the application is working with another system to extract values for them and then saving. I can't recreate the error The error logs show: The error happend at the same time in both the application Both happend on a Attach/Submit (but two different functions) There is no way they are using the same DataContext object as I save the DataContext in the HttpContext.Items My hunch / guess is: One datacontext was not refreshed i.e. the an object was created for the same item twice as it was new in both the forms. eg. Customer Number - a customer was created (as one couldn't be found) by one datacontext - the other one couldn't find it either (i am using compiled queries to find it in the datacontext) so it created another object and on attaching failed. The HttpContext.Items lost its value somehow (i am using a virtual pc as server - maybe something went wrong there) I am going more of the second as I can't recreate the error - but it just might be a timing (for attach/save) thing - also the error makes me think of the 2nd too.

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  • Is there a more efficent way to randomise a set of linq results?

    - by Matthew De'Loughry
    Hi just wondering if you could help I've produced a function to get back a random set of submission depnding on the amount passed to it, but I worry that even though it works now with a small amount of data when the a large amount is passed through it would become efficent and cause problems. Just wondering if you could suggest a more efficent way of doing the following: public List<Submission> GetRandomWinners(int id) { List<Submission> submissions = new List<Submission>(); int amount = (DbContext().Competitions .Where(s => s.CompetitionId == id).FirstOrDefault()).NumberWinners; for(int i = 1 ; i <= amount; i++) { bool added = false; while (!added) { bool found = false; var randSubmissions = DbContext().Submissions .Where(s => s.CompetitionId == id && s.CorrectAnswer).ToList(); int count = randSubmissions.Count(); int index = new Random().Next(count); foreach (var sub in submissions ) { if (sub == randSubmissions.Skip(index).FirstOrDefault()) found = true; } if (!found) { submissions.Add(randSubmissions.Skip(index).FirstOrDefault()); added = true; } } } return submissions; } As I say I have this fully working and bringing back the wanted result just I'm not liking the foreach and while checks in there and my head has just turned to mush now try to come up with the above soloution. Thanks Matt

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  • Why is this linq extension method hit the database twice?

    - by Pure.Krome
    Hi folks, I have an extension method called ToListIfNotNullOrEmpty(), which is hitting the DB twice, instead of once. The first time it returns one result, the second time it returns all the correct results. I'm pretty sure the first time it hits the database, is when the .Any() method is getting called. here's the code. public static IList<T> ToListIfNotNullOrEmpty<T>(this IEnumerable<T> value) { if (value.IsNullOrEmpty()) { return null; } if (value is IList<T>) { return (value as IList<T>); } return new List<T>(value); } public static bool IsNullOrEmpty<T>(this IEnumerable<T> value) { if (value != null) { return !value.Any(); } return true; } I'm hoping to refactor it so that, before the .Any() method is called, it actually enumerates through the entire list. If i do the following, only one DB call is made, because the list is already enumerated. var pewPew = (from x in whatever select x) .ToList() // This enumerates. .ToListIsNotNullOrEmpty(); // This checks the enumerated result. I sorta don't really want to call ToList() then my extension method. Any ideas, folks?

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  • ASP MVC LINQ to SQL IQueryable Array out of bounds?

    - by Jacob Huggart
    Hey guys, I have an Iqueryable that is populated from the database and then converted to an Array. That works fine. The issue is when I only have 1 element in the Array. I try to use the 0th element and it says "ArrayOutOfBoundsException". When I have 2+ elements in the array and pull elements 0 and 1 it works fine. What gives?

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  • What is the best way to return result from business layer to presentation layer when using linq - I

    - by samsur
    I have a business layer that has DTOs that are used in the presentation layer. This application uses entity framework. Here is an example of a class called RoleDTO public class RoleDTO { public Guid RoleId { get; set; } public string RoleName { get; set; } public string RoleDescription { get; set; } public int? OrganizationId { get; set; } } In the BLL I want to have a method that returns a list of DTO.. I would like to know which is the better approach: returning IQueryable or list of DTOs. Although i feel that returning Iqueryable is not a good idea because the connection needs to be open. Here are the 2 different methods using the different approaches public class RoleBLL { private servicedeskEntities sde; public RoleBLL() { sde = new servicedeskEntities(); } public IQueryable<RoleDTO> GetAllRoles() { IQueryable<RoleDTO> role = from r in sde.Roles select new RoleDTO() { RoleId = r.RoleID, RoleName = r.RoleName, RoleDescription = r.RoleDescription, OrganizationId = r.OrganizationId }; return role; } Note: in the above method the datacontext is a private attribute and set in the constructor, so that the connection stays opened. Second approach public static List GetAllRoles() { List roleDTO = new List(); using (servicedeskEntities sde = new servicedeskEntities()) { var roles = from pri in sde.Roles select new { pri.RoleID, pri.RoleName, pri.RoleDescription }; //Add the role entites to the DTO list and return. This is necessary as anonymous types can be returned acrosss methods foreach (var item in roles) { RoleDTO roleItem = new RoleDTO(); roleItem.RoleId = item.RoleID; roleItem.RoleDescription = item.RoleDescription; roleItem.RoleName = item.RoleName; roleDTO.Add(roleItem); } return roleDTO; } Please let me know, if there is a better approach - Thanks,

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  • Can I make this two LINQ queries into one query only?

    - by Holli
    From a List of builtAgents I need all items with OptimPriority == 1 and only 5 items with OptimPriority == 0. I do this with two seperate queries but I wonder if I could make this with only one query. IEnumerable<Agent> priorityAgents = from pri in builtAgents where pri.OptimPriority == 1 select pri; IEnumerable<Agent> otherAgents = (from oth in builtAgents where oth.OptimPriority == 0 select oth).Take(5);

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  • My Linq to Sql Insert code seems to work fine but I don't get a record in the database

    - by Alex
    Here is my code. In the debugger, I can see that the code is running. No errors are thrown. But, when I go back to the table, no row has been inserted. What am I missing?? protected void submitButton_Click(object sender, EventArgs e) { CfdDataClassesDataContext db = new CfdDataClassesDataContext(); string sOfficeSought = officesSoughtDropDownList.SelectedValue; int iOfficeSought; Int32.TryParse(sOfficeSought, out iOfficeSought); Account act = new Account() { FirstName = firstNameTextBox.Text, MiddleName = middleNamelTextBox.Text, LastName = lastNameTextBox.Text, Suffix = suffixTextBox.Text, CampaignName = campaignNameTextBox.Text, Address1 = address1TextBox.Text, Address2 = address2TextBox.Text, TownCity = townCityTextBox.Text, State = stateTextBox.Text, ZipCode = zipTextBox.Text, Phone = phoneTextBox.Text, Fax = faxTextBox.Text, PartyAffiliation = partyAfilliatinoTextBox.Text, EmailAddress = emailTextBox.Text, BankName = bankNameTextBox.Text, BankMailingAddress = bankAddressTextBox.Text, BankTownCity = bankTownCityTextBox.Text, BankState = bankStateTextBox.Text, BankZip = bankZipTextBox.Text, TreasurerFirstName = treasurerFirstNameTextBox.Text, TreasurerMiddleName = treasurerMiddleNamelTextBox.Text, TreasurerLastName = treasurerLastNameTextBox.Text, TreasurerMailingAddress = treasurerMailingAddressTextBox.Text, TreasurerTownCity = treasurerTownCityTextBox.Text, TreasurerState = treasurerStateTextBox.Text, TreasurerZipCode = treasurerZipTextBox.Text, TreasurerPhone = treasurerPhoneTextBox.Text //OfficeSought = iOfficeSought }; act.Suffix = suffixTextBox.Text; db.SubmitChanges(); }

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  • How to compare a string column(as DateTime) in LINQ?

    - by lyon
    I have a database with a ValidDate field - it's a string(we made a mistake, it should be a datetime, but we can't modify the database now.) and now I want to compare this filed with a parameter(validDateStart) from the website: priceList = priceList.Where(p => Convert.ToDateTime(p.ValidDate) >= Convert.ToDateTime(validDateStart)); var list = initPriceList.ToList(); But I get an error: The method ToDateTime is not implemented. Can anybody give me some help? Thanks!

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  • Cannot add an entity that already exists. (LINQ to SQL)

    - by Vicheanak
    Hello guys, in my database there are 3 tables CustomerType CusID EventType EventTypeID CustomerEventType CusID EventTypeID Dim db = new CustomerEventDataContext Dim newEvent = new EventType newEvent.EventTypeID = txtEventID.text db.EventType.InsertOnSubmit(newEvent) db.SubmitChanges() 'To select the last ID of event' Dim lastEventID = (from e in db.EventType Select e.EventTypeID Order By EventTypeID Descending).first() Dim chkbx As CheckBoxList = CType(form1.FindControl("CheckBoxList1"), CheckBoxList) Dim newCustomerEventType = New CustomerEventType Dim i As Integer For i = 0 To chkbx.Items.Count - 1 Step i + 1 If (chkbx.Items(i).Selected) Then newCustomerEventType.INTEVENTTYPEID = lastEventID newCustomerEventType.INTSTUDENTTYPEID = chkbxStudentType.Items(i).Value db.CustomerEventType.InsertOnSubmit(newCustomerEventType) db.SubmitChanges() End If Next It works fine when I checked only 1 Single ID of CustomerEventType from CheckBoxList1. It inserts data into EventType with ID 1 and CustomerEventType ID 1. However, when I checked both of them, the error message said Cannot add an entity that already exists. Any suggestions please? Thx in advance.

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  • How do I return the ancestors of an object with LINQ?

    - by Chris
    I have a District class that looks like this: public class District { public int Id { get; set; } public string Name { get; set; } public District Parent { get; set; } public IEnumerable<District> Ancestors { get { /* what goes here? */ } } } I would like to be able to get a list of each District's ancestors. So if District "1.1.1" is a child of District "1.1", which is a child of District "1", getting Ancestors on District "1.1.1" would return a list that contains the District objects whose names are "1.1" and "1". Does this involve the yield return statement (I never totally understood that)? Can it be done in one line?

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  • How can I use linq to initialize an array of repeated elements?

    - by Eric
    At present, I'm using something like this to build a list of 10 objects: myList = (from _ in Enumerable.Range(0, 9) select new MyObject {...}).toList() This is based off my python background, where I'd write: myList = [MyObject(...) for _ in range(10)] Note that I want my list to contain 10 instances of my object, not the same instance 10 times. Is this still a sensible way to do things in C#? Is there a cost to doing it this way over a simple for loop?

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  • How do i set Savepoints for Linq to SQL and use "NO" ExecuteCommand ?

    - by nik
    TransactionScope TransactionABC = new TransactionScope(); try { context.Connection.Open(); { context.ExecuteCommand("insert into test (test) values (1)") context.SubmitChanges(); context.ExecuteCommand("savepoint test"); context.ExecuteCommand("insert into test (test) values (2)") context.SubmitChanges(); context.ExecuteCommand("rollback to test"); } TransactionABC.Complete(); TransactionABC.Dispose(); } catch (Exception ec) { MessageBox.Show(" ", ec.Message); } finally { context.Connection.Close(); } It works, but only with ExecuteCommand. I want to use a function, because i can't see what happens in the savepoint !

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  • How can I use Linq to create an array of dictionaries from XML?

    - by Duke
    Given the following XML structure: <courses> <course> <title>foo</title> <description>bar</description> </course> ... </courses> How could I create an array of dictionaries such that each dictionary contains all the element/value pairs within a course? What I have right now generates an array whose elements contain a single key/value dictionary for each element/value pair in a course: XElement x = XElement.Parse("...xml string..."); var foo = (from n in x.Elements() select n) .Elements().ToDictionary(y => y.Name, y => y.Value); Produces: [0] => {[course, foo]} [1] => {[description, bar]} What I'd like is this: [0] => {[course, foo], [description, bar]}

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  • What's the meaning of the angle brackets on LINQ methods in Intellisense? (Contains<>, Count<>, Dis

    - by user312758
    They usually involve generics. But some methods with generics don't have them, and not all extension methods have them. They've just "been there" since day one, we've all seen them; but I realized I still don't know what they mean, and I can't find the answer anywhere. Now it's really bugging me. Google just turns up results that are about XML, etc. Is this officially documented anywhere? Thanks. EDIT: Well that's just great. Since I just created an account to make my first Stack Overflow post, to get an answer for this burning question; I'm not allowed to post my pretty Intellisense picture, or create a new tag "angle-brackets". I love Stack Overflow, but... what a welcome! Maybe my problem is that they aren't actually called "angle brackets"... ?? Anyway, I guess if you really want to see my beautiful screenshot you could manually go to: http://www.freeimagehosting.net/uploads/6a6c2f3268.png Bump me up please so I can include it in the post, thanks. ;)

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