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• Cannot implicitly convert type System.Collection.Generic.IEnumberable

  - by Cen

  I'm receiving this error in my Linq statement --- Cannot implicitly convert type 'System.Collections.Generic.IEnumerable' to 'hcgames.ObjectClasses.ShoppingCart.ShoppingCartCartAddon'. An explicit conversion exists (are you missing a cast?) From this query ShoppingCartItems items = Cart.GetAllItems(); ShoppingCartCartAddons addons = Cart.GetAllAddons(); var stuff = from x in items select new ShoppingCartItem() { ProductID = x.ProductID, Quantity = x.Quantity, Name = x.Name, Price = x.Price, Weight = x.Weight, Addons = (from y in addons where y.ShoppingCartItemID == x.ID select y) }; I can not figure out how to cast this properly. Any suggestions? Thanks for your help!

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• Treat multiple IEnumerable objects as a single IEnumerable

  - by MainMa

  Hi, My question seems to be something easy, but I can't figure it out. Let's say I have a "root" IEnumerable of objects. Each object has IEnumerable of strings. How can I obtain a single IEnumerable of those strings? A possible solution is to do: public IEnumerable<string> DoExample() { foreach (var c in rootSetOfObjects) { foreach (var n in c.childSetOfStrings) { yield return n; } } } But maybe there is a magic solution with Linq?

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• Sequence Generators in T-SQL

  - by PaoloFCantoni

  We have an Oracle application that uses a standard pattern to populate surrogate keys. We have a series of extrinsic rows (that have specific values for the surrogate keys) and other rows that have intrinsic values. We use the following Oracle trigger snippet to determine what to do with the Surrogate key on insert: 'IF :NEW.SurrogateKey IS NULL THEN SELECT SurrogateKey_SEQ.NEXTVAL INTO :NEW.SurrogateKey FROM DUAL; END IF;' If the supplied surrogate key is null then get a value from the nominated sequence, else pass the supplied surrogate key through to the row. I can't seem to find an easy way to do this is T-SQL. There are all sorts of approaches, but none of which use the notion of a sequence generator like Oracle and other SQL-92 compliant DBs do. Anybody know of a really efficient way to do this in SQL Server T-SQL? BTW we're using SQL Server 2008 if that's any help. TIA, Paolo

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• How can I access IEnumerable<T> extension methods on my custom subclass of BindingList<T>?

  - by Dan

  I have a custom subclass of BindingList<T> that I want to execute a LINQ query over using the handy extension methods. For example: public int GetSum(MyList<T> list) { return list.Sum(x => x.Value); } But the compiler complains that it can't resolve Sum because it doesn't recognize list as an IEnumerable<T>, which it obviously is, because this works: public int GetSum(MyList<T> list) { return ((IEnumerable<T>)list).Sum(x => x.Value); } Anyone have a clever way I can avoid the ugly and unecessary cast?

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• Will there be IQueryable-like additions to IObservable? (.NET Rx)

  - by Jason

  The new IObservable/IObserver frameworks in the System.Reactive library coming in .NET 4.0 are very exciting (see this and this link). It may be too early to speculate, but will there also be a (for lack of a better term) IQueryable-like framework built for these new interfaces as well? One particular use case would be to assist in pre-processing events at the source, rather than in the chain of the receiving calls. For example, if you have a very 'chatty' event interface, using the Subscribe().Where(...) will receive all events through the pipeline and the client does the filtering. What I am wondering is if there will be something akin to IQueryableObservable, whereby these LINQ methods will be 'compiled' into some 'smart' Subscribe implementation in a source. I can imagine certain network server architectures that could use such a framework. Or how about an add-on to SQL Server (or any RDBMS for that matter) that would allow .NET code to receive new data notifications (triggers in code) and would need those notifications filtered server-side.

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• LINQtoSQL: Query to return List<String>

  - by ctrlShiftBryan

  I have a LINQ query that returns some object like this... var query = from c in db.Customers where ... select c; Then I do this List<String> list = new List<String>(); foreach (ProgramLanguage c in query) { //GetUL returns a String list.Add(GetUL(c.Property,c.Property2)); } Is there a way to combine into something list this? var query = from c in db.Customers where ... select new { GetUL(c.Property,c.Property2) }).ToList<String>();

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• Extraction Event

  - by Anicho

  So I have the following code: public override void Extract(object sender, ExtractionEventArgs e) { if (e.Response.HtmlDocument != null) { var myParam = e.Request.QueryStringParameters.Where(parameter => parameter.Name == QueryName).Select(parameter => parameter.Value).Distinct(); myParam. // add the extracted value to the web performance test context e.WebTest.Context.Add(this.ContextParameterName, myParam.ToString()); e.Success = true; return; } // If the extraction fails, set the error text that the user sees e.Success = false; e.Message = String.Format(CultureInfo.CurrentCulture, "Not Found: {0}", QueryName); } It's returning: System.Linq.Enumerable+<DistinctItem>d_81`1[system.string] I am expecting something along the lines of: 0152-1231-1231-123d My question is how do I extract the querystring's actual value from extractioneventargs. They say it's possible, but I have no idea.

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• How to replace for-loops with a functional statement in C#?

  - by Lernkurve

  A colleague once said that God is killing a kitten every time I write a for-loop. When asked how to avoid for-loops, his answer was to use a functional language. However, if you are stuck with a non-functional language, say C#, what techniques are there to avoid for-loops or to get rid of them by refactoring? With lambda expressions and LINQ perhaps? If so, how? Questions So the question boils down to: Why are for-loops bad? Or, in what context are for-loops to avoid and why? Can you provide C# code examples of how it looks before, i.e. with a loop, and afterwards without a loop?

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• Property in class is IEnumerable<TDto> get TDto.A == a

  - by Miau

  So I have a class is something like this public class Order { //some other stuff ... //setting the internal _orderItems collection ... IEnumerable<OrderItems> OrderItems { get { return _orderItems; } } public class OrderItem { //other stuff public string ProductName {get; set;} } If I have a collection of orders of some sort and have access via linq to the order, something like myOrderRespository.Where(x=>x.OrderItems) Then I only have access to getEnumerator there, waht I would like it to be able to do something like myOrderRespository.Where(x=>x.OrderItems.ProductName == "Blah") Is this possible? this is a made up scenario and its pseudo code I m trying to simplify the problem so its easy to explain ( so please forgive me if there are a few errors) Cheers

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• Please help me translate C# code to Ruby

  - by Valentin Vasilyev

  Here is the code: using System; using System.Collections.Generic; using System.Linq; namespace cs2 { class Program { static void Main(string[] args) { var i=Fibs.TakeWhile(x=>x < 1000).Where(x=>x % 2==0).Sum(); } static IEnumerable<long> Fibs() { long a = 0, b = 1; while (true) { yield return b; b += a; a = b - a; } } } }

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• Perl DBI - run SQL Script with multiple statements

  - by guigui42

  I have a sql file test.sql used to run some SQL (create object / update / delete / insert) that can look like this CREATE TABLE test_dbi1 ( test_dbi_intr_no NUMBER(15) , test_dbi_name VARCHAR2(100); UPDATE mytable SET col1=1; CREATE TABLE test_dbi2 ( test_dbi_intr_no NUMBER(15) , test_dbi_name VARCHAR2(100); Usually, i would just use SQLPLUS (from within Perl) to execute this test.sql using this command : @test.sql Is there a way to do the same thing, using DBI in Perl ? So far, i found DBI can only execute one statement at a time, and without the ";" at the end.

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• Why am I getting "Collection was modified; enumeration operation may not execute" when not modifying

  - by ccornet

  I have two collections of strings: CollectionA is a StringCollection property of an object stored in the system, while CollectionB is a List generated at runtime. CollectionA needs to be updated to match CollectionB if there are any differences. So I devised what I expected to be a simple LINQ method to perform the removal. var strDifferences = CollectionA.Where(foo => !CollectionB.Contains(foo)); foreach (var strVar in strDifferences) { CollectionA.Remove(strVar); } But I am getting a "Collection was modified; enumeration operation may not execute" error on strDifferences... even though it is a separate enumerable from the collection being modified! I originally devised this explicitly to evade this error, as my first implementation would produce it (as I was enumerating across CollectionA and just removing when !CollectionB.Contains(str)). Can anyone shed some insight into why this enumeration is failing?

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• What is my problem with ASP.NET pubslishing?

  - by Shankarooni

  I am done testing my site and I want to upload it to a site like this http://www.university.edu/mydepartment/myname the admin told me the server runs on .NET 3.5. So i used Linq ... now i tried to upload the site by two ways: when i just copy everything (with modification of web.config database settings) i get an error: CS0246: The type or namespace name 'DataClassesDataContext' could not be found (are you missing a using directive or an assembly reference?) Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082 Note here it says version 2.0 did he just lie to me? or its my configuration mistake? anyway, i added the reference, nothing changes. I tried also publishing (Build, publish) with option to keep the pre-comiled site updatable, and I get one line saying: this is a makefile and should be deleted! what is going on?

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• Comparing 2 objects and retrive a list of fields with different values

  - by ajj

  Hi given a class with 35 fields and 2 objects with a certain number of different fields value. is there an clever way to get a list with the fields name where the objext Say obj1.Name = "aaa"; obj1.LastName = "bbb"; obj1.Address = "xcs"; obj2.Name = "aaa"; obj2.LastName = "ccc"; obj2.Address = "jk"; objective: list containing 2 strings LastName and Address I see reflection as the way to go but with 35 fields I am afraid it s to heavy. Any other idea, like linq? Thanks, a.

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• Calculating holidays

  - by Ralph Shillington

  A number of holidays move around from year to year. For example, in Canada Victoria day (aka the May two-four weekend) is the Monday before May 25th, or Thanksgiving is the 2nd Monday of October (in Canada). I've been using variations on this Linq query to get the date of a holiday for a given year: var year = 2011; var month = 10; var dow = DayOfWeek.Monday; var instance = 2; var day = (from d in Enumerable.Range(1,DateTime.DaysInMonth(year,month)) let sample = new DateTime(year,month,d) where sample.DayOfWeek == dow select sample).Skip(instance-1).Take(1); While this works, and is easy enough to understand, I can imagine there is a more elegant way of making this calculation versus this brute force approach. Of course this doesn't touch on holidays such as Easter and the many other lunar based dates.

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• Using VirtualMode on a DataGridView when the number of rows/columns isn't known

  - by Nathan Baulch

  I need to display an unknown length sequence of dictionaries with unknown keys efficiently in a data grid. This sequence is the result of a potentially slow LINQ query that could contain any number of results. At first I thought that VirtualMode on DataGridView was what I was looking for but it appears that the number of rows and columns must be known upfront. I tried adding a single row and column then adding more as needed from the CellValueNeeded event but this doesn't work. Is this even possible with VirtualMode? Or do I need to estimate how many rows are visible on the screen and manually build up the rows/columns? And if so, how do I ensure that a vertical scrollbar is present and react appropriately when a user uses it?

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• How to return arrays with the biggest elements in C#?

  - by theateist

  I have multiple int arrays: 1) [1 , 202,4 ,55] 2) [40, 7] 3) [2 , 48 ,5] 4) [40, 8 ,90] I need to get the array that has the biggest numbers in all positions. In my case that would be array #4. Explanation: arrays #2, #4 have the biggest number in 1st position, so after the first iteration these 2 arrays will be returned ([40, 7] and [40, 8 ,90]) now after comparing 2nd position of the returned array from previous iteration we will get array #4 because 8 7 and so on... Can you suggest an efficient algorithm for this? Doing with Linq will be preferable. UPDATE There is no limitation for the length, but as soon as some number in any position is greater, so this array is the biggest.

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• Auto-generated values for columns in database

  - by Jamal

  Is it a good practice to initialize columns that we can know their values in database, for example identity columns of type unique identifier can have a default value (NEWID()), or columns that shows the record create date can have a default value (GETDATE()). Should I go through all my tables and do this whereever I am sure that I won't need to assign the value manually and the Auto-generated value is correct. I am also thinking about using linq-to-sql classes and setting the "Auto Generated Value" property of these columns to true. Maybe this is what everybody already knows or maybe I am asking a question about a fundamental issue, if so please tell me.

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• How extension methods work in background ?

  - by Freshblood

  I am just cuirous about behind of extension method mechanism.Some questions and answer appear in my mind. MyClass.OrderBy(x=>x.a).OrderBy(x=>x.b); I was guessing that mechanism was first orderby method works and order them by a member then returns sorted items in IEnumarable interface then next Orderby method of IEnumarable Order them for b paramater.But i am wrong when i look at this linq query. MyClass.Orderby(x=>x.a).ThenOrderBy(x=>x.b); this is slightly different and tells me that i am wrong.Because this is not ordering by a then b and not possible to have such result if i was right.This get me confuse enough... Similiar structure is possible to write withot extension methods as first query but second is not possible.This prove i am wrong . Can u explain it ?

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• Php/ODBC encoding problem

  - by JohnM2

  I use ODBC to connect to SQL Server from PHP. In PHP I read some string (nvarchar column) data from SQL Server and then want to insert it to mysql database. When I try to insert such value to mysql database table I get this mysql error: Incorrect string value: '\xB3\xB9ow...' for column 'name' at row 1 For string with all ASCII characters everything is fine, the problem occurs when non-ASCII characters (from some European languages) exist. So, in more general terms: there is a Unicode string in MS SQL Server database, which is retrieved by PHP trough ODBC. Then it is put in sql insert query (as value for utf-8 varchar column) which is executed for mysql database. Can someone explain to me what is happening in this situation in terms of encoding? At which step what character encoding convertions may take place? I use: PHP 5.2.5, MySQL5.0.45-community-nt, MS Sql Server 2005.

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• Convert date from access to SQL Server with SSIS

  - by Arne

  Hi, I want to convert a database from access to SQL Server using SSIS. I cannot convert the date/time columns of the access db. SSIS says something like: conversion between DT_Date and DT_DBTIMESTAMP is not supported. (Its translated from my German version, might be different in English version). In Access I have Date/Time column, in SQL Server I have datetime. In the dataflow chart of the SSIS I have a OLE DB source for the access db, an sql server target and a data conversion. In the data conversion I convert the columns to date[DT_DATE]. They are connected like this: AccessDB -> conversion -> SQL DB What am I doing wrong? How can I convert the Access date columns to SQL Server date columns?

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• Error(2,7): PLS-00428: an INTO clause is expected in this SELECT statement

  - by omgzor

  I'm trying to create this trigger and getting the following compiler errors: create or replace TRIGGER RESTAR_PLAZAS AFTER INSERT ON PLAN_VUELO BEGIN SELECT F.NRO_VUELO, M.CAPACIDAD, M.CAPACIDAD - COALESCE(( SELECT count(*) FROM PLAN_VUELO P WHERE P.NRO_VUELO = F.NRO_VUELO ), 0) as PLAZAS_DISPONIBLES FROM VUELO F INNER JOIN MODELO M ON M.ID = F.CODIGO_AVION; END RESTAR_PLAZAS; Error(2,7): PL/SQL: SQL Statement ignored Error(8,5): PL/SQL: ORA-00933: SQL command not properly ended Error(8,27): PLS-00103: Encountered the symbol "end-of-file" when expecting one of the following: begin case declare end exception exit for goto if loop mod null pragma raise return select update while with <an identifier> <a double-quoted delimited-identifier> <a bind variable> << close current delete fetch lock insert open rollback savepoint set sql execute commit forall merge pipe Error(2,1): PLS-00428: an INTO clause is expected in this SELECT statement What's wrong with this trigger?

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• LINQ2SQL: how to merge two columns from the same table into a single list

  - by TomL

  this is probably a simple question, but I'm only a beginner so... Suppose I have a table containing home-work locations (cities) certain people use. Something like: ID(int), namePerson(string), homeLocation(string), workLocation(string) where homeLocation and workLocation can both be null. Now I want all the different locations that are used merged into a single list. Something like: var homeLocation = from hm in Places where hm.Home != null select hm.Home; var workLocation = from wk in Places where wk.Work != null select wk.Work; List<string> locationList = new List<string>(); locationList = homeLocation.Distinct().ToList<string>(); locationList.AddRange(workLocation.Distinct().ToList<string>()); (which I guess would still allow duplicates if they have the same value in both columns, which I don't really want...) My question: how this be put into a single LINQ statement? Thanks in advance for your help!

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• How would you write this C# code succinctly in Ruby?

  - by Valentin Vasilyev

  Here is the code: using System; using System.Collections.Generic; using System.Linq; namespace cs2 { class Program { static void Main(string[] args) { var i=Fibs().TakeWhile(x=>x < 1000).Where(x=>x % 2==0).Sum(); } static IEnumerable<long> Fibs() { long a = 0, b = 1; while (true) { yield return b; b += a; a = b - a; } } } } If it is possible, please give an example.

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• Do I need to include all fields in my entity framework model

  - by Jim B

  Quick question for everyone: Do I need to include all the database table fields on my EF model? For example; I've created a sub-model that only deals with tblPayment and associated tables. Now, I need to write a LINQ query to get some information about items. I would typically get this by joining tblPayment to tblInvoice to tblInvoiceItem to finally tblOrderItem. I'm wondering if when I add in those other tables, do I need to include all the fields for tblInvoice and tblInvoiceItem? Ideally; I'd just like to keep the fields I'd need to join on, as that would limit the possibility of my sub-model breaking if other fields on those tables are modified/deleted. Can I do this?

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