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  • EF 4 Query - Issue with Multiple Parameters

    - by Brian
    Hello, A trick to avoiding filtering by nullable parameters in SQL was something like the following: select * from customers where (@CustomerName is null or CustomerName = @CustomerName) This worked well for me in LINQ to SQL: string customerName = "XYZ"; var results = (from c in ctx.Customers where (customerName == null || (customerName != null && c.CustomerName == customerName)) select c); But that above query, when in ADO.NET EF, doesn't work for me; it should filter by customer name because it exists, but it doesn't. Instead, it's querying all the customer records. Now, this is a simplified example, because I have many fields that I'm utilizing this kind of logic with. But it never actually filters, queries all the records, and causes a timeout exception. But the wierd thing is another query does something similarly, with no issues. Any ideas why? Seems like a bug to me, or is there a workaround for this? I've since switched to extension methods which works. Thanks.

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  • How to initialize list with parent child relation

    - by user2917702
    Let's say I have the following classes. public class Parent { public string name; IList<Children> children; } public class Child { public string parentName; public int age; } As it is understandable, each parent can have multiple children, and we can have multiple parents. What is the best way to initialize these classes? Is it better to get all of the parents, and all of the children from database then use LINQ? IList<Parent> parents = GetParents()//assume this gets parents from db IList<Child> children = GetChildren() //assume this gets children from db foreach(Parent parent in parents) { parent.children = children.Where(x=>x.parentName==parent.name).ToList(); } or get all of the parents and iterate through each parent to query database by parentName to get children information? Due to requirement that I have, I cannot use datatable or dataset; I can only use datareader. IList<Parent> parents = GetParents()//assume this gets parents from db foreach(Parent parent in parents) { parent.children = GetChildrenByParentName();//assume this gets parents from db by parentName } Thank you

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  • How to break an object into chunks based on some property?

    - by CurlyFro
    public class InvestorMailing { public string To { get; set; } public IEnumerable<string> Attachments { get; set; } public int AttachmentCount { get; set; } public long AttachmentSize { get; set; } } i have an IList<InvestorMailing> mailingList. if the attachment size is greater than x, then i need to split my object into chunks. is there an easy linq-y way to do this? Edited: this is how i'm generating my mailings: var groupedMailings = mailingList.GroupBy(g => g.GroupBy); var investorMailings = groupedMailings.Select( g => new DistinctInvestorMailing { Id = g.Select(x => x.Id).FirstOrDefault(), To = g.Key.Trim(), From = g.Select(x => x.From).FirstOrDefault(), FromName = g.Select(x => x.FromName).FirstOrDefault(), Bcc = g.Select(x => x.Bcc).FirstOrDefault(), DeliveryCode = g.Select(x => x.DeliveryCode).FirstOrDefault(), Subject = g.Select(x => x.Subject).FirstOrDefault(), Body = g.Select(x => x.Body).FirstOrDefault(), CommentsOnStatus = g.Select(x => x.CommentsOnStatus).FirstOrDefault(), Attachments = g.Select(x => x.AttachmentPath), AttachmentCount = g.Select(x => x.AttachmentPath).Count(), AttachmentSize = g.Sum(x => x.AttachmentSize), MailType = g.Select(x => x.MessageType).FirstOrDefault() } ).ToList();

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  • A good(elegant) way to retrieve records with counts.

    - by user93422
    Context: ASP.NET MVC 2.0, C#, SQL Server 2007, IIS7 I have 'scheduledMeetings' table in the database. There is a one-to-many relationship: scheduledMeeting - meetingRegistration So that you could have 10 people registered for a meeting. meetingRegistration has fields Name, and Gender (for example). I have a "calendar view" on my site that shows all coming events, as well as gender count for each event. At the moment I use Linq to Sql to pull the data: var meetings = db.Meetings.Select( m => new { MeetingId = m.Id, Girls = m.Registrations.Count(r => r.Gender == 0), Boys = m.Registrations.Count(r=>r.Gender == 1) }); (actual query is half-a-page long) Because there is anonymous type use going on I cant extract it into a method (since I have several different flavors of calendar view, with different information on each, and I dont want to create new class for each). Any suggestions on how to improve this? Is database view is the answer? Or should I go ahead and create named-type? Any feedback/suggestions are welcome. My DataLayer is huge, I want to trim it, just dont know how. Pointers to a good reading would be good too.

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  • How to convert object to string list?

    - by user1381501
    I want to get two values by using linq select query and try to convert object to string list. I am trying to convert list to list. The code as below. I got the error when I convert object to string list : return returnvalue = (List)userlist; public List<string> GetUserList(string username) { List<User> UserList = new List<User>(); List<string> returnvalue=new List<string>(); try { string returnstring = string.Empty; DataTable dt = null; dt = Library.Helper.FindUser(username, 200); foreach (DataRow dr in dt.Rows) { User user = new User(); spuser.id = dr["ID"].ToString(); spuser.name = dr["Name"].ToString(); UserList.Adduser } } catch (Exception ex) { } List<SharePointMentoinUser> userlist = UserList.Select(a => new User { name = (string)a.name, id = (string)a.id }).ToList(); **return returnvalue = (List<string>)userlist;** }

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  • List of running minimum values

    - by scarle88
    Given a sorted list of: new []{1, 2, -1, 3, -2, 1, 1, 2, -1, -3} I want to be able to iterate over the list and at each element return the smallest value iterated so far. So given the list above the resultant list would look like: 1 1 -1 -1 -2 -2 -2 -2 -2 -3 My rough draft code looks like: var items = new []{1, 2, -1, 3, -2, 1, 1, 2, -1, -3}; var min = items.First(); var drawdown = items.Select(i => { if(i < min) { min = i; return i; } else { return min; } }); foreach(var i in drawdown) { Console.WriteLine(i); } But this is not very elegant. Is there an easier to read (linq?) way of doing this? I looked into Aggregate but it seemed to be the wrong tool. Ultimately the list of items will be very long, in the many thousands. So good performance will be an issue to.

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  • LINQ to Entities Projection of Nested List

    - by Matthew
    Assuming these objects... class MyClass { int ID {get;set;} string Name {get;set;} List<MyOtherClass> Things {get;set;} } class MyOtherClass { int ID {get;set;} string Value {get;set;} } How do I perform a LINQ to Entities Query, using a projection like below, that will give me a List? This works fine with an IEnumerable (assuming MyClass.Things is an IEnumerable, but I need to use List) MyClass myClass = (from MyClassTable mct in this.Context.MyClassTableSet select new MyClass { ID = mct.ID, Name = mct.Name, Things = (from MyOtherClass moc in mct.Stuff where moc.IsActive select new MyOtherClass { ID = moc.ID, Value = moc.Value }).AsEnumerable() }).FirstOrDefault(); Thanks in advance for the help!

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  • split a list using linq

    - by Anonym
    I've the following code: var e = someList.GetEnumerator(); var a = new List<Foo>(); var b = new List<Foo>(); while(e.MoveNext()) { if(CheckCondition(e.Current)) { b.Add(e.Current); break; } a.Add(e.Current); } while(e.MoveNext()) b.Add(e.Current) This looks ugly. Basically, iterate through a list and add elements to one list until some condition kicks in, and add the rest to another list. Is there a better way e.g. using linq ? CheckCondition() is expensive, and the lists can be huge so I'd prefer to not do anything that iterates the lists twice.

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  • exception with Linq to SQL using sdf file

    - by Ben
    Hi, I've set up a project with an SDF local database file and am trying to access it using an LINQ To SQL (".dbml") file. I have used the connection string provided by the sdf file and can instanciate the object with out a problem: thisDataContext = new MyDataContext(GetConnectionString()); However, whenever i try to access any information from it eg var collection = (from MyObject p in thisDataContext.MyTable select p); I get the error - "The table name is not valid. [ Token line number (if known) = 2,Token line offset (if known) = 14,Table name = Person ]" I am using Visual Studio 2008 SP1 .Net 3.5 and SQL 2008 CE. I gather something similar happened for SQL 2005 CE and a Hotfix was released, but i would have thought the fix would have been fixed in this version before release. Does anyone know the fix for this? Thanks

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  • linq Except and custom IEqualityComparer

    - by Joe
    I'm trying to implement a custom comparer on two lists of strings and use the .Except() linq method to get those that aren't one one of the lists. The reason I'm doing a custom comparer is because I need to do a "fuzzy" compare, i.e. one string on one list could be embedded inside a string on the other list. I've made the following comparer ` public class ItemFuzzyMatchComparer : IEqualityComparer { bool IEqualityComparer<string>.Equals(string x, string y) { return (x.Contains(y) || y.Contains(x)); } int IEqualityComparer<string>.GetHashCode(string obj) { if (Object.ReferenceEquals(obj, null)) return 0; return obj.GetHashCode(); } } ` When I debug, the only breakpoint that hits is in the GetHashCode() method. The Equals() never gets touched. Any ideas?

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  • Listing subdirectories 3 levels deep using LINQ C#

    - by paradox
    I'd like to know if there is a better alternative to my following code (preferably using LINQ) #region List and filter directories to only 3 levels deep // List all subdirectories within main directory string[] folders = Directory.GetDirectories(@"C:\pdftest\", "*" ,SearchOption.AllDirectories); List<string> subdirectories = new List<string>(); //Filter away all main directories, now we are left with subdirectories 3 levels deep for (int i = 0; i<folders.Length; i++) { int occurences = folders[i].Split('\\').Length-1; if (occurences==4) subdirectories.Add(folders[i]); } #endregion

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  • dotConnect LINQ to MySQL Issue

    - by Saravanan I M
    I am using dotConnect LINQ to MySQL and i have the following error. what would be the cause for this issue annot convert parameter value of type 'System.String' to MySQL type 'MySqlType.TimeStamp'. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidCastException: Cannot convert parameter value of type 'System.String' to MySQL type 'MySqlType.TimeStamp'. Source Error: Line 93: { Line 94: string loginLowered = login.ToLower(); Line 95: return context.ISVs.Where(u = u.Email == loginLowered).SingleOrDefault() == null; Line 96: Line 97: }

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  • ASP.NET MVC2 - using LINQ-generated class

    - by ile
    There are few things not clear to me about ASP.NET MV2. In database I have table Contacts with several fields, and there is an additional field XmlFields of which type is xml. In that field are stored additional description fields. There are 4 classes: Contact class which corresponds to Contact table and is defined by default when creating LINQ classes ContactListView class which inherits Contact class and has some additional properties ContactXmlView class that contains fields from XmlFields field ContactDetailsView class which merges ContactListView and ContactXmlView into one class and this one is used to display data in view pages ContactListView class has re-defined some properties from Contact class (so that I can add [Required] filter used for validation) - but I get warning message: 'ObjectTest.Models.Contacts.ContactListView.FirstName' hides inherited member 'SA.Model.Contact.FirstName'. Use the new keyword if hiding was intended. ContactDetailsView class is also used in a form when creating new contact and adding it to database. I am not sure if this is correct way, and the warning message confuses me a bit. Any advise about this? Thanks, Ile

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  • NHibernate.Linq to Criteria API translation help needed

    - by Arnis L.
    I'm not sure how to add paging to this: Session.Linq<Article>() .Where(art => art.Tags.Any(t => t.Name == tag)).ToList(). So i decided to use Criteria API. var rowCount = Session.CreateCriteria(typeof(Article)) .SetProjection(Projections.RowCount()).FutureValue<Int32>(); var res = Session.CreateCriteria(typeof(Article)) .Add(/* any help with this? :) */) .SetFirstResult(page * pageSize) .SetMaxResults(pageSize) .AddOrder(new Order("DatePublish", true)) .Future<Article>(); totalCount = rowCount.Value; Any help appreciated.

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  • Subsonic linq using activerecord very slow compared to simplerepository

    - by skiik
    Anyone know anything about why linq queries are about 6 times slower when querying using active record vs simplerepository? The below code runs 6 times slower than when i query the data using a simple repository. This code is executed 1000 times in a loop Thanks in advance string ret = ""; // if (plan == null) { plan =VOUCHER_PLAN.SingleOrDefault(x => x.TENDER_TYPE == tenderType); } if (plan == null) throw new InvalidOperationException("voucher type does not exist." + tenderType); seq = plan.VOUCHER_SEQUENCES.First(); int i = seq.CURRENT_NUMBER; seq.CURRENT_NUMBER += seq.STEP; seq.Save();

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  • Can't Add LINQ to SQL classes to projects in VS2010

    - by MisterJames
    I just ran into something in Visual Studio 2010 RC that wasn't previously happening (like, yesterday). No software changes here, but I did run into some muck yesterday when compiling that required a reboot. I am unable to add LINQ to SQL classes to any project through the add dialog. I have created ASP.NET web sites, ASP.NET MVC projects - both of these as 'templated' and as 'empty' - and there appear to be no templates installed or available. I have made sure that the project targets the 4.0 Framework. I can easily add a new database and the ADO.NET entity framework templates are there. As a workaround I can copy a DBML file to my project, delete all tables and sprocs, update the connection string and use the leftover shell (the designer works fine like this), but it's a pain. Has anyone else had their templates drop? Figured out how to reinstall them?

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  • Any clever way to fix 'string or binary data would be truncated' warning with LINQ

    - by Simon_Weaver
    Is there a clever way to determine which field is causing 'string or binary data would be truncated' with LINQ. I've always ended up doing it manually by stepping through a debugger, but with a batch using 'SubmitChanges' I have to change my code to inserting a single row to find the culprit in a batch of rows. Am I missing something or in this day and age do I really have to still use a brute force method to find the problem. Please dont give me advice on avoiding this error in future (unless its something much cleverer than 'validate your data'). The source data is coming from a different system where I dont have full control anyway - plus I want to be lazy. PS. Does SQL Server 2008 actually tell me the field name. Please tell me it does! I'll upgrade!

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  • LINQ Join for Orderby only

    - by RandomBen
    I am trying to run this code: ItemTaxonomy iTaxonomy = from itemTaxonomy in connection.ItemTaxonomy where itemTaxonomy.Item.ID == itemView.ID orderby itemTaxonomy.Taxonomy.Name select itemTaxonomy; When I compiled it I get the error: Cannot implicitly convert type 'System.Linq.IOrderedQueryable<Website.Models.ItemTaxonomy>' to 'Website.Models.ItemTaxonomy'. An explicit conversion exists (are you missing a cast?) I believe the issue is with orderby itemTaxonomy.Taxonomy.Name but I am just trying to order by the name of Taxonomy items instead of their IDs. Is there a way to do that?

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  • C# Linq: Restructuring object

    - by Ben
    I'd like to take an object like this: SortedList<string, SortedList<int, SortedList<DateTime, double>>> Data and, for a given 'int' value (key of first nested sorted list), restructure it like this: SortedList<DateTime, SortedList<string, double>> or, better yet, this: SortedList<DateTime, double[]> where each 'double[]' has as many elements as there are KeyValue pairs in the SortedList. I'm guessing Linq is the way to go, but can't figure it out. Thanks for any suggestions.

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  • How to write simple code in LInq

    - by user281180
    I have the following in my NotSelectedList. public List<TestModel> SelectedList = new List<TestModel>(); public List<TestModel>NotSelectedList = new List<TestModel>(); NotificationDetailsModel projects = new NotificationDetailsModel(); projects.ProjectID = Convert.ToInt32(Row["ProjectID"]); projects.Valid= Convert.ToBoolean(Row["Validity"]); NotSelectedList.Add(projects); How can I write a simple code in LINQ to select from the NotSelectedList where Validity == True and store the data in SelectedList?

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  • linq Multiple Where based on conditions.

    - by Bathan
    I want to query a table with some conditions based on user input. I wrote this : IQueryable turnoQuery = dc.Turno; if (helper.FechaUltimaCitaDesde != DateTime.MinValue) { turnoQuery = turnoQuery.Where(t => t.TurnoFecha >= helper.FechaUltimaCitaDesde); } if (helper.FechaUltimaCitaHasta != DateTime.MinValue) { turnoQuery = turnoQuery.Where(t => t.TurnoFecha <= helper.FechaUltimaCitaHasta); } if (helper.SoloCitasConsumidas) { turnoQuery = turnoQuery.Where(t => t.Estado == Convert.ToInt32(EnmEstadoDelTurno.Consumido)); } else if(helper.AnuladoresDeCitas) { turnoQuery = turnoQuery.Where(t => t.Estado == Convert.ToInt32(EnmEstadoDelTurno.Cancelado) || t.Estado == Convert.ToInt32(EnmEstadoDelTurno.Ausente)); } The problem I'm having is that the "where" clause gets stepped over with the last one. Whats the correct way to do something like this on LINQ? The "helper" object is a custom class storing the user input dates for this example.

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  • Help needed to write a LINQ with GROUP bY(C#3.0)

    - by Newbie
    I have a datatable whose structure is as under Week Dates Key_Factors Factor_Values --- ----- ----------- ------------- 1 29/12/2000 Factor_1 19.20 1 29/12/2000 Factor_2 20.67 1 29/12/2000 Factor_3 10 2 21/12/2007 Factor_1 20.54 2 21/12/2007 Factor_4 21.70 I have a Object model like WeekNumber(int) Dates(Datetime) FactorDictionary (Dictionary<string,double>) I am trying to populate the data from DataTable to my Object Model whose needed output is as under Desired Output ---------------- WeekNumber : 1 Dates : 29/12/2000 FactorDictionary: Key_Factors: Factor_1 Factor_Values:19.20 Key_Factors: Factor_2 Factor_Values:20.67 Key_Factors: Factor_3 Factor_Values:10 WeekNumber : 2 Dates : 21/12/2007 FactorDictionary: Key_Factors: Factor_1 Factor_Values:20.54 Key_Factors: Factor_4 Factor_Values:21.70 i.e. The result is grouped by weeks. Can I achieve the same by using LINQ. I am using C#(3.0) with framework(3.5) Thanks

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  • C# Unit Testing - Generating Mock DataContexts / LINQ -> SQL classes

    - by gav
    Hi All, I am loving the new world that is C#, I've come to a point with my toy programs where I want to start writing some unit tests. My code currently uses a database via a DatabaseDataContext object (*.dbml file), what's the best way to create a mock for this object? Given how easy it is to generate the database LINQ - SQL code and how common a request this must be I'm hoping that VS2010 has built in functionality to help with testing. If I'm way off and this must be done manually could you please enlighten me as to your preferred approach? Many Thanks, Gavin

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  • Linq to Entities (EF): How to get the value of a FK without doing the join

    - by Chu
    I'm using the Linq to Entities. I've got my main table, Employee setup with a field named vendorID. Vendor ID is a foreign key into the Vendors table. As it is right now, the Employee object does not directly expose the vendorID. Instead, I can only access it this way: var employee = (from e in context.Employees.Include("tbl_vendors") where e.employeeID = 1 select e).FirstOrDefault(); //this gets the vendor ID int vendorID = employee.tbl_vendors.vendorID; That is just fine and dandy, but it is extra work on the database because it is forcing a join where none is needed. Is there a way to get that key value without being forced to do a join to the tbl_vendors table?

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  • LINQ Query based on user preferences

    - by Chris Phelps
    How can I do this better (so it actually works : ) I have a LINQ Query that includes an order by that is based on a user preference. The user can decide if they would like the results ordered asc or desc. If fuserclass.SortOrder = "Ascending" Then Dim mydat = (From c In dc.ITRS Order By c.Date Ascending Select c) Else Dim mydat = (From c In dc.ITRS Order By c.Date Descending Select c) End If For each mydata in mydat ***<<<error "mydat is not declared"*** I know I could put my For Each loop inside the If and Else, but that seems silly to have the same code twice. I know you know of a better way : )

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