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  • Searching with Linq

    - by Phil
    I have a collection of objects, each with an int Frame property. Given an int, I want to find the object in the collection that has the closest Frame. Here is what I'm doing so far: public static void Search(int frameNumber) { var differences = (from rec in _records select new { FrameDiff = Math.Abs(rec.Frame - frameNumber), Record = rec }).OrderBy(x => x.FrameDiff); var closestRecord = differences.FirstOrDefault().Record; //continue work... } This is great and everything, except there are 200,000 items in my collection and I call this method very frequently. Is there a relatively easy, more efficient way to do this?

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  • How to use linq to find the minimum

    - by Danvil
    I have a class A { public float Score; ... } and a List<A> items and would like to find the A which has minimal score. Using items.Min(x => x.Score) gives the minimal score and not the instance with minimal score. How can I get the instance with only iterating once through my Collection?

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  • Dynamic Linq query issue

    - by Alex
    Hey All, Im trying to query the Netflix OData feed. I have the following query that works fine in LinqPad: from g in Genres from t in g.Titles where g.Name == "Horror" && t.AverageRating == 2 && t.ReleaseYear == 2004 select t But, when I move it over to my Silverlight app, the user selects what to search on so I may or may not have all of the params. That being the case, I need to construct the query at runtime. Ive looked the the Dynamic Query stuff and that will do fine...the issue that I have is that I need an initial acceptable query to append to and this doesn't fly: from g in Genres from t in g.Titles select t; Any additional thoughts would be appreciated. Thanks in advance

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  • LINQ Query returns nothing.

    - by gtas
    Why is this query returns 0 lines? There is a record matching the arguments. Deafkaw.Where(p => (p.ImerominiaKataxorisis >= aDate && p.ImerominiaKataxorisis <= DateTime.Now) && (p.Year == etos && p.IsYpodeigma == false) ).ToList(); Am i missing something?

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  • linq expression in vb.net

    - by Thurein
    Hi, Can any body translate the following c# code to vb. I have tried telarik code converter but I got problem at expression.call and it won't compile at all. private static IOrderedQueryable<T> OrderingHelper<T>(IQueryable<T> source, string propertyName, bool descending, bool anotherLevel) { ParameterExpression param = Expression.Parameter(typeof(T), string.Empty); MemberExpression property = Expression.PropertyOrField(param, propertyName); LambdaExpression sort = Expression.Lambda(property, param); MethodCallExpression call = Expression.Call( typeof(Queryable), (!anotherLevel ? "OrderBy" : "ThenBy") + (descending ? "Descending" : string.Empty), new[] { typeof(T), property.Type }, // error line source.Expression, Expression.Quote(sort)); return (IOrderedQueryable<T>)source.Provider.CreateQuery<T>(call); } thanks Thurein

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  • How to bind gridview using linq/Entity Framework?

    - by Kay
    I need to bind GridView, I am using this code: ProductDBEntities db = new ProductPDBEntities(); var pro = from u in db.Products where u.PID == 1 select u; if (pro != null) { GridView1.DataSource = pro; GridView1.DataBind(); } and getting this error. System.InvalidOperationException: Sequence contains more than one element Can somebody please tell me what am I doin wrong?

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  • Linq DateTime expressions wont compare if only one is nullable

    - by tigermain
    I have been getting the following exception: The binary operator GreaterThanOrEqual is not defined for the types 'System.Nullable`1[System.DateTime]' and 'System.DateTime'. I am getting the left hand expression from a class property which is a nullable datetime variable and my right hand side is using Expression.Constant(new Nullable<DateTime>(DateTime.Now)) However I still get the above exception despite explicitly setting the right hand expression to a nullable type

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  • LINQ to SQL: On load processing of lazy loaded associations

    - by Matt Holmes
    If I have an object that lazy loads an association with very large objects, is there a way I can do processing at the time the lazy load occurs? I thought I could use AssociateWith or LoadWith from DataLoadOptions, but there are very, very specific restrictions on what you can do in those. Basically I need to be notified when an EntitySet< decides it's time to load the associated object, so I can catch that event and do some processing on the loaded object. I don't want to simply walk through the EntitySet when I load the parent object, because that will force all the lazy loaded items to load (defeating the purpose of lazy loading entirely).

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  • LINQ query null reference exception

    - by user289082
    Hi! I have the next query: var bPermisos = from b in ruc.Permisos where b.IdUsuario == cu.Id select new Permisos(){ Id=b.Id, IdUsuario=b.Id, IdPerfil=b.Id, Estatus=b.Estatus }; var qSisPer = from perm in bPermisos select new { perm.IdPerfil,perm.Cat_Perfil.Nivel,perm.Cat_Perfil.Nombre,Nombre_Sistem=perm.Cat_Perfil.Cat_Sistema.Nombre}; And is throwing me an exception, plz help!

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  • Comparison operators not supported for type IList when Paging data in Linq to Sql

    - by Dan
    I can understand what the error is saying - it can't compare a list. Not a problem, other than the fact that I don't know how to not have it compare a list when I want to page through a model with a list as a property. My Model: Event : IEvent int Id string Title // Other stuff.. LazyList<EventDate> Dates // The "problem" property Method which pages the data (truncated): public JsonResult JsonEventList(int skip, int take) { var query = _eventService.GetEvents(); // Do some filtering, then page data.. query = query.Skip(skip).Take(take); return Json(query.ToArray()); } As I said, the above is truncated quite a bit, leaving only the main point of the function: filter, page and return JSON'd data. The exception occurs when I enumerate (.ToArray()). The Event object is really only used to list the common objects of all the event types (Meetings, Birthdays, etc - for example). It still implements IEvent like the other types, so I can't just remove the LazyList<EventDate> Dates' property unless I no longer implementIEvent` Anyway, is there a way to avoid this? I don't really want to compare a LazyList when I page, but I do not know how to resolve this issue. Thank you in advance! :)

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  • linq to sql loadwith vs associatewith

    - by stackoverflowuser
    what is the difference between loadwith and associatewith. From the articles i read it seems that loadwith is used to load addition data (eg all orders for the customers). While AssociateWith is used to filter data. Is that a correct understanding? Also it will be nice if someone can explain this with an example based explanation.

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  • LINQ to SQL: making a "double IN" query crashes

    - by Alex
    I need to do the following thing: var a = from c in DB.Customers where (from t1 in DB.Table1 where t1.Date >= DataTime.Now select t1.ID).Contains(c.ID) && (from t2 in DB.Table2 where t2.Date >= DataTime.Now select t2.ID).Contains(c.ID) select a It doesn't want to run. I get the following error: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. But when I try to run var a = from c in DB.Customers where (from t1 in DB.Table1 where t1.Date >= DataTime.Now select t1.ID).Contains(c.ID) select a OR var a = from c in DB.Customers where (from t2 in DB.Table2 where t2.Date = DataTime.Now select t2.ID).Contains(c.ID) select a It works! I'm sure that there both IN queries contain some customers ids.

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  • DB4o Linq query - How to check for null strings

    - by Dave
    Hey there - simple query: var q = (from SomeObject o in container where o.SomeInt > 8 && o.SomeString != null //Null Ref here select o; I always get a null reference exception. If I use String.IsNullOrEmpty(o.SomeString) the query takes about 100 times as long, as if I use && o.SomeString != "" (which is way faster, but obviously not correct). I'm guessing because DB4o needs to activate the objects, in order to pass them in to the IsNullOrEmpty call, and can't use the indexes. My question is, what's a better way to check for nulls in this situation? Is there something like: mystring != Db4o.DBNull.Value, or something? Cheers, Dave

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  • linq multiple order DESCENDING

    - by ile
    .OrderBy(y => y.Year).ThenBy(m => m.Month); How to set descending order? EDIT: I tried this: var result = (from dn in db.DealNotes where dn.DealID == dealID group dn by new { month = dn.Date.Month, year = dn.Date.Year } into date orderby date.Key.year descending orderby date.Key.month descending select new DealNoteDateListView { DisplayDate = date.Key.month + "-" + date.Key.year, Month = date.Key.month, Year = date.Key.year, Count = date.Count() }) //.OrderBy(y => y.Year).ThenBy(m => m.Month) ; And it seems working. Is it wrong to use orderby twice like I used it here?

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  • Hos to group the complex list objects by using Linq

    - by Daoming Yang
    I want to select and group the products, and rank them by the number of times they occur. For example, I have an OrderList each of order object has a OrderProductVariantList(OrderLineList), and each of OrderProductVariant object has ProductVariant, and then the ProductVariant object will have a Product object which contains product information. A friend helped me with the following code. It could be compiled, but it did not return any value/result. I used the watch window for the query and it gave me "The name 'query' does not exist in the current context". Can anyone help me? Many thanks. var query = orderList.SelectMany( o => o.OrderLineList ) // results in IEnumerable<OrderProductVariant> .Select( opv => opv.ProductVariant ) .Select( pv => p.Product ) .GroupBy( p => p ) .Select( g => new { Product = g.Key, Count = g.Count() });

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  • Parallelizing some LINQ to XML

    - by Lol coder
    How can I make this code run in parallel? List<Crop> crops = new List<Crop>(); //Get up to 10 pages of data. for (int i = 1; i < 10; i++) { //i is basically used for paging. XDocument document = XDocument.Load(string.Format(url, i)); crops.AddRange(from c in document.Descendants("CropType") select new Crop { //The data here. }); }

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  • LINQ-TO-XML not returning all value

    - by mmcglynn
    I am trying to get all values in the select. using item.Count shows the correct number of values, but only one .Value is returned from the loop. Why? Dim fooXML As XDocument = XDocument.Load(Server.MapPath("xml/foo.xml")) Dim query = _ From c In fooXML...<foobaryear> _ Select c...<event> For Each item In query Response.Write(item.Value) Next

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  • LINQ, Left Join, Only Get where null in join table

    - by kmehta
    Hi. I am trying to do a left outer join on two tables, but I only want to return the results from the first table where the second table does not have a record (null). var agencies = from a in agencyList join aa in joinTable on a.AgencyId equals aa.AgencyId into joined from aa in joined.DefaultIfEmpty() where aa == null) select a; But this does not exclude the non null values of aa, and returns all the records just the same as if the 'where aa == null' was not there. Any help is appreciated. Thanks.

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  • LINQ to Sql: Insert instead of Update

    - by Christina Mayers
    I am stuck with this problems for a long time now. Everything I try to do is insert a row in my DB if it's new information - if not update the existing one. I've updated many entities in my life before - but what's wrong with this code is beyond me (probably something pretty basic) I guess I can't see the wood for the trees... private Models.databaseDataContext db = new Models.databaseDataContext(); internal void StoreInformations(IEnumerable<EntityType> iEnumerable) { foreach (EntityType item in iEnumerable) { EntityType type = db.EntityType.Where(t => t.Room == item.Room).FirstOrDefault(); if (type == null) { db.EntityType.InsertOnSubmit(item); } else { type.Date = item.Date; type.LastUpdate = DateTime.Now(); type.End = item.End; } } } internal void Save() { db.SubmitChanges(); } Edit: just checked the ChangeSet, there are no updates only inserts. For now I've settled with foreach (EntityType item in iEnumerable) { EntityType type = db.EntityType.Where(t => t.Room == item.Room).FirstOrDefault(); if (type != null) { db.Exams.DeleteOnSubmit(type); } db.EntityType.InsertOnSubmit(item); } but I'd love to do updates and lose these unnecessary delete statements.

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  • Linq Aggregate function

    - by Nyla Pareska
    I have a List like "test", "bla", "something", "else" But when I use the Aggrate on it and in the mean time call a function it seems to me that after 2 'iterations' the result of the first gets passed in? I am using it like : myList.Aggregate((current, next) => someMethod(current) + ", "+ someMethod(next)); and while I put a breakpoint in the someMethod function where some transformation on the information in the myList occurs, I notice that after the 3rd call I get a result from a former transformation as input paramter.

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  • SQL & Linq To SQL Help

    - by cre-johnny07
    I have a table which is some thing like below.. Date ID 2009-07-01 1 2009-07-01 2 2009-07-01 3 2009-08-01 4 2009-08-01 5 2009-08-01 6 2009-09-01 7 2009-09-01 8 2009-10-01 9 2009-10-01 10 2009-11-01 11 .... Now I need to write a query which will show a output like below. Date Start End 2009-07 1 3 2009-08 4 6 2009-09 7 8 ... How can I do this.. Any help would be highly appreciated Thanking In Advance Johnny

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  • Like query ing LINQ to Object

    - by Pankaj
    Hello All i have a US states list List<string> state // contain all 51 US states Now i have a string which contain some text like okl (it means Oklahoma for me). what i want i want 'like' query in List state and get Oklahoma state.

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  • LINQ Data Context Not Showing Methods

    - by CccTrash
    For some reason my DataContext is not showing all the normal methods like SubmitChanges() etc in the intellisense. It also won't compile if I type in db.SubmitChanges(); Any idea what I'm doing wrong? Normally I don't have this issue, I have several other projects that work fine... Image of what I'm talking about:

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  • Linq - get compare with transliterated value of fields

    - by Maxim
    Hi! I have a table (sql server). One of its columns ('Name') Contains Cyrillic values. From parameters i recieve value, that contains in this field but the are transliterated. i mean something like: var q = from r in m_DataContext.Table where CTransliteration.Transliterate(r.Name).Contains(trans_text) select r; How can i transliterate value on-fly?

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