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• Using LINQ to filter rows of a matrix based on inclusion in an array

  - by Bob Feng

  I have a matrix, IEnumerable<IEnumerable<int>> matrix, for example: { {10,23,16,20,2,4}, {22,13,1,33,21,11 }, {7,19,31,12,6,22}, ... } and another array: int[] arr={ 10, 23, 16, 20} I want to filter the matrix on the condition that I group all rows of the matrix which contain the same number of elements from arr. That is to say the first row in the matrix {10,23,16,20,2,4} has 4 numbers from arr, this array should be grouped with the rest of the rows with 4 numbers from arr. better to use linq, thank you very much!

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• SQL to LINQ translating probem

  - by ognjenb

  I have problem with convertion this SQL statement to LINQ : SELECT a.Id, a.Name, a.ArtiklNumber, a.Notes, a.Weight, l.StartDate AS LastStartDate, l.LocationNameId, loc.Name AS CarrentLocation, a.Reserved FROM Accessories a LEFT OUTER JOIN Location l LEFT JOIN LocationName loc ON l.LocationNameId = loc.Id ON a.Id = (SELECT AccessoriesId FROM Location WHERE AccessoriesId = a.Id HAVING MAX(StartDate) = StartDate ) This is part of my translated code: testEntities6 accessoriesEntities = new testEntities6(); var max_StartDate = (from msd in accessoriesEntities.location from d in accessoriesEntities.device where msd.DeviceId == d.Id select msd.StartDate).Min(); var accessories_query = from accs in accessoriesEntities.accessories join l in accessoriesEntities.location on accs.Id equals l.AccessoriesId join loc in accessoriesEntities.locationname on l.LocationNameId equals loc.Id select new AccessoriesModel { //Accessories Id = accs.Id, Name = accs.Name, ArtiklNumber = accs.ArtiklNumber, Notes = accs.Notes, Weight = accs.Weight, Reserved = accs.Reserved, //Location LocationNameId = l.LocationNameId, StartDate = max_StartDate,//l.StartDate, //Locationname Loc_name = loc.Name };

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• Linq to CSV select by column

  - by griegs

  If I have the following (sample) text file; year,2008,2009,2010 income,1000,1500,2000 dividends,100,200,300 net profit,1100,1700,2300 expenses,500,600,500 profit,600,1100,1800 Is there a way in Linq that I can select the expenses for 2010 only? So far I have the following which gets me all the data; var data = File.ReadAllLines(fileName) .Select( l => { var split = l.CsvSplit(); return split; } ); foreach (var item in data) Console.WriteLine("{0}: ${1}", item[0], item[1]);

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• Select a Dictionary<T1, T2> with LINQ

  - by Rich

  I have used the "select" keyword and extension method to return an IEnumerable<T> with LINQ, but I have a need to return a generic Dictionary<T1, T2> and can't figure it out. The example I learned this from used something in a form similar to the following: IEnumerable<T> coll = from x in y select new SomeClass{ prop1 = value1, prop2 = value2 }; I've also done the same thing with extension methods. I assumed that since the items in a Dictionary<T1, T2> can be iterated as KeyValuePair<T1, T2> that I could just replace "SomeClass" in the above example with "new KeyValuePair<T1, T2> { ...", but that didn't work (Key and Value were marked as readonly, so I could not compile this code). Is this possible, or do I need to do this in multiple steps? Thanks.

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• Linq - Grouping where items fall in multiple groups?

  - by PirateKitten

  Is it possible using Linq to create a group where items fall into more than one group? Using the following trivial example: public class Data { public string ID; public int From; public int To; } And this list: List<Data> data = new List<Data>() { new Data() { ID = "A", From = 1, To = 3 }, // Call this A new Data() { ID = "B", From = 1, To = 2 }, // Call this B new Data() { ID = "C", From = 2, To = 3 } // Call this C }; I'd like to group by each possible integer in the ranges From and To (though instead of finding the min + max I could supply the query with the range I want, for example 1 to 3), and in each group would be a reference to the Data instance where the grouping int fits in its range. Hard to explain, easier to show each group and the instances I'd expect in each: [Group 1] 1 - A, B [Group 2] 2 - A, B, C [Group 3] 3 - A, C Is this possible? Or must groups be mutually exclusive?

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• Constructor or Explicit cast

  - by Felan

  In working with Linq to Sql I create a seperate class to ferry data to a web page. To simplify creating these ferry objects I either use a specialized constructor or an explicit conversion operator. I have two questions. First which approach is better from a readibility perspective? Second while the clr code that is generated appeared to be the same to me, are there situations where one would be treated different than the other by the compiler (in lambda's or such). Example code (DatabaseFoo uses specialized constructor and BusinessFoo uses explicit operator): public class DatabaseFoo { private static int idCounter; // just to help with generating data public int Id { get; set; } public string Name { get; set; } public DatabaseFoo() { Id = idCounter++; Name = string.Format("Test{0}", Id); } public DatabaseFoo(BusinessFoo foo) { this.Id = foo.Id; this.Name = foo.Name; } } public class BusinessFoo { public int Id { get; set; } public string Name { get; set; } public static explicit operator BusinessFoo(DatabaseFoo foo) { return FromDatabaseFoo(foo); } public static BusinessFoo FromDatabaseFoo(DatabaseFoo foo) { return new BusinessFoo {Id = foo.Id, Name = foo.Name}; } } public class Program { static void Main(string[] args) { Console.WriteLine("Creating the initial list of DatabaseFoo"); IEnumerable<DatabaseFoo> dafoos = new List<DatabaseFoo>() { new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo(), new DatabaseFoo()}; foreach(DatabaseFoo dafoo in dafoos) Console.WriteLine(string.Format("{0}\t{1}", dafoo.Id, dafoo.Name)); Console.WriteLine("Casting the list of DatabaseFoo to a list of BusinessFoo"); IEnumerable<BusinessFoo> bufoos = from x in dafoos select (BusinessFoo) x; foreach (BusinessFoo bufoo in bufoos) Console.WriteLine(string.Format("{0}\t{1}", bufoo.Id, bufoo.Name)); Console.WriteLine("Creating a new list of DatabaseFoo by calling the constructor taking BusinessFoo"); IEnumerable<DatabaseFoo> fufoos = from x in bufoos select new DatabaseFoo(x); foreach(DatabaseFoo fufoo in fufoos) Console.WriteLine(string.Format("{0}\t{1}", fufoo.Id, fufoo.Name)); } }

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• Loading the last related record instantly for multiple parent records using Entity framework

  - by Guillaume Schuermans

  Does anyone know a good approach using Entity Framework for the problem described below? I am trying for our next release to come up with a performant way to show the placed orders for the logged on customer. Of course paging is always a good technique to use when a lot of data is available I would like to see an answer without any paging techniques. Here's the story: a customer places an order which gets an orderstatus = PENDING. Depending on some strategy we move that order up the chain in order to get it APPROVED. Every change of status is logged so we can see a trace for statusses and maybe even an extra line of comment per status which can provide some extra valuable information to whoever sees this order in an interface. So an Order is linked to a Customer. One order can have multiple orderstatusses stored in OrderStatusHistory. In my testscenario I am using a customer which has 100+ Orders each with about 5 records in the OrderStatusHistory-table. I would for now like to see all orders in one page not using paging where for each Order I show the last relevant Status and the extra comment (if there is any for this last status; both fields coming from OrderStatusHistory; the record with the highest Id for the given OrderId). There are multiple scenarios I have tried, but I would like to see any potential other solutions or comments on the things I have already tried. Trying to do Include() when getting Orders but this still results in multiple queries launched on the database. Each order triggers an extra query to the database to get all orderstatusses in the history table. So all statusses are queried here instead of just returning the last relevant one, plus 100 extra queries are launched for 100 orders. You can imagine the problem when there are 100000+ orders in the database. Having 2 computed columns on the database: LastStatus, LastStatusInformation and a regular Linq-Query which gets those columns which are available through the Entity-model. The problem with this approach is the fact that those computed columns are determined using a scalar function which can not be changed without removing the formula from the computed column, etc... In the end I am very familiar with SQL and Stored procedures, but since the rest of the data-layer uses Entity Framework I would like to stick to it as long as possible, even though I have my doubts about performance. Using the SQL approach I would write something like this: WITH cte (RN, OrderId, [Status], Information) AS ( SELECT ROW_NUMBER() OVER (PARTITION BY OrderId ORDER BY Id DESC), OrderId, [Status], Information FROM OrderStatus ) SELECT o.Id, cte.[Status], cte.Information AS StatusInformation, o.* FROM [Order] o INNER JOIN cte ON o.Id = cte.OrderId AND cte.RN = 1 WHERE CustomerId = @CustomerId ORDER BY 1 DESC; which returns all orders for the customer with the statusinformation provided by the Common Table Expression. Does anyone know a good approach using Entity Framework?

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• Linq to SQL EntitySet Binding the MVVM way

  - by Savvas Sopiadis

  Hi everybody! In a WPF application i'm using LINQ to SQL classes (created by SQL Metal, thus implementing POCOs). Let's assume i have a table User and a Table Pictures. These pictures are actually created from one picture, the difference between them may be the size, coloring,... So every user may has more than one Pictures, so the association is 1:N (User:Pictures). My problems: a) how do i bind, in a MVVM manner, a picture control to one picture (i will take one specific picture) in the EntitySet, to show it up? b) everytime a user changes her picture the whole EntitySet should be thrown away and the newly created Picture(s) should be a added. Is this the correct way? e.g. //create the 1st piture object UserPicture1 = new UserPicture(); UserPicture1.Description = "... some description.. "; USerPicture1.Image = imgBytes; //array of bytes //create the 2nd piture object UserPicture2 = new UserPicture(); UserPicture2.Description = "... another description.. "; UserPicture2.Image = DoSomethingWithPreviousImg(imgBytes); //array of bytes //Assuming that the entityset is called Pictures //add these pictures to the corresponding user User.Pictures.Add(UserPicture1); User.Pictures.Add(UserPicture2); //save changes datacontext.Save() Thanks in advance

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• LINQ-to-SQL: ExecuteQuery(Type, String) populates one field, but not the other

  - by Daniel Schaffer

  I've written an app that I use as an agent to query data from a database and automatically load it into my distributed web cache. I do this by specifying an sql query and a type in a configuration. The code that actually does the querying looks like this: List<Object> result = null; try { result = dc.ExecuteQuery(elementType, entry.Command).OfType<Object>().ToList(); } catch (Exception ex) { HandleException(ex, WebCacheAgentLogEvent.DatabaseExecutionError); continue; } elementType is a System.Type created from the type specified in the configuration (using Type.GetType()), and entry.Command is the SQL query. The specific entity type I'm having an issue with looks like this: public class FooCount { [Column(Name = "foo_id")] public Int32 FooId { get; set; } [Column(Name = "count")] public Int32 Count { get; set; } } The SQL query looks like this: select foo_id as foo_id, sum(count) as [count] from foo_aggregates group by foo_id order by foo_id For some reason, when the query is executed, the "Count" property ends up populated, but not the "FooId" property. I tried running the query myself, and the correct column names are returned, and the column names match up with what I've specified in my mapping attributes. Help!

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• Return an empty collection when Linq where returns nothing

  - by ahsteele

  I am using the below statement with the intent of getting all of the machine objects from the MachineList collection (type IEnumerable) that have a MachineStatus of i. The MachineList collection will not always contain machines with a status of i. At times when no machines have a MachineStatus of i I'd like to return an empty collection. My call to ActiveMachines (which is used first) works but InactiveMachines does not. public IEnumerable<Machine> ActiveMachines { get { return Customer.MachineList .Where(m => m.MachineStatus == "a"); } } public IEnumerable<Machine> InactiveMachines { get { return Customer.MachineList .Where(m => m.MachineStatus == "i"); } } Edit Upon further examination it appears that any enumeration of MachineList will cause subsequent enumerations of MachineList to throw an exeception: Object reference not set to an instance of an object. Therefore, it doesn't matter if a call is made to ActiveMachines or InactiveMachines as its an issue with the MachineList collection. This is especially troubling because I can break calls to MachineList simply by enumerating it in a Watch before it is called in code. At its lowest level MachineList implements NHibernate.IQuery being returned as an IEnumerable. What's causing MachineList to lose its contents after an initial enumeration?

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• Existing LINQ extension method similar to Parallel.For?

  - by Joel Martinez

  The linq extension methods for ienumerable are very handy ... but not that useful if all you want to do is apply some computation to each item in the enumeration without returning anything. So I was wondering if perhaps I was just missing the right method, or if it truly doesn't exist as I'd rather use a built-in version if it's available ... but I haven't found one :-) I could have sworn there was a .ForEach method somewhere, but I have yet to find it. In the meantime, I did write my own version in case it's useful for anyone else: using System.Collections; using System.Collections.Generic; public delegate void Function<T>(T item); public delegate void Function(object item); public static class EnumerableExtensions { public static void For(this IEnumerable enumerable, Function func) { foreach (object item in enumerable) { func(item); } } public static void For<T>(this IEnumerable<T> enumerable, Function<T> func) { foreach (T item in enumerable) { func(item); } } } usage is: myEnumerable.For<MyClass>(delegate(MyClass item) { item.Count++; });

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• SQLce DAL Linq to Sql or EntityFramework

  - by bretddog

  Hi, I'm learning databases, using SqlCe, and need business object to database mapping. Currently I try to decide if to use Linq to Sql, or EntityFramework. (I understand a bit L2S, but haven't familiarized with EF yet) The program will only be debeloped and used by myself, so I have good control of the priorities: I don't need to consider potential change of database type or data storage type, as I'm quite certain SQLce will stay sufficient. I DO expect continued development and changes to the data scheme while the program is in active use; change business object properties (Hence database columns), and possibly overall table scheme. So old data must be transported to new scheme. I also want to keep a decent degree of layer separation DAL/BLL, although this may not be necessary, it is good for me to learn these principles. My question is: With these priorities, would I have any benefit by choosing either Linq2Sql vs. EntityFramwork? (and please explain why) Btw, the project involves very simple table scheme with only 4-5 tables and very simple relations. Thanks!

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• How to select a single object using Linq in vb.net

  - by Hucker

  I have done a lot of searching to what appears to be a simple LINQ problem but I can't figure out how to do grab an object out of a collection that has a specified minimum (or max value) without resorting to a sort like this: > dim customers= GetCustomers() > > dim youngest = (From c in customers > Order By c.age Ascending).ToList.First This (untested code) structure works fine with the exception that the entire customer array must be sorted and placed into a list for the only purpose of extracting the first value. That can't be the best way to get the minimum! Note that I want the whole c record in this case, not the minumum age of a customer that can be done like this (a typical example): > dim customers= GetCustomers() > > dim youngest = (From c in customers > Select c.age).Min Or even > dim customers= GetCustomers() > > dim youngest = (From c in customers > Select c).Min(Function(x) x.age) I can't for the life of me figure out how to get the whole object (or even the index) without resorting to the sort...

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• Nested function inside literal Object...

  - by Andrea

  Hello guys, if in a literal object i try to reference a function using "this" inside a nested property/function, this don't work. Why? A nested property have it's own scope? For example, i want to call f1 from inside d.f2: var object = { a: "Var a", b: "Var b", c: "Var c", f1: function() { alert("This is f1"); }, d: { f2: function() { this.f1(); } }, e: { f3: function() { alert("This is f3"); } } } object.f1(); // Work object.d.f2(); // Don't Work. object.e.f3(); // Work Thanks, Andrea.

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• Implementation of a general-purpose object structure (property bag)

  - by Thomas Wanner

  We need to implement some general-purpose object structure, much like an object in dynamic languages, that would give us a possibility of creating the whole object graph on-the-fly. This class has to be serializable and somehow user friendly. So far we have made some experiments with class derived from Dictionary<string, object> using the dot notation path to store properties and collections in the object tree. We have also find an article that implements something similar, but it doesn't seem to fit completely into our picture either. Do you know about some good implementations / libraries that deal with a similar problem or do you have any (non-trivial) ideas that could help us with our own implementation ? Also, I probably have to say that we are using .NET 3.5, so we can't take advantage of the new features in .NET 4.0 like dynamic type etc. (as far as I know it's also not possible to use any subset of it in .NET 3.5 solution).

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• Zipping Rx IObservable with infinite number set

  - by Toni Kielo

  I have a IObservable [named rows in the sample below] from Reactive extensions framework and I want to add index numbers to each object it observes. I've tried to implement this using Zip function: rows.Zip(Enumerable.Range(1, int.MaxValue), (row, index) => new { Row = row, Index = index }) .Subscribe(a => ProcessRow(a.Row, a.Index), () => Completed()); .. but unfortunately this throws ArgumentOutOfRangeException: Specified argument was out of the range of valid values. Parameter name: disposables Am I understanding the Zip function wrong or is there a problem with my code? The Range part of the code doesn't seem to be the problem and the IObservable isn't yet receiving any events.

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• stringtemplate .net dynamic object

  - by Mark Milford

  Hi I am using string template to render some content, but the content may be variable so not sure how to pass it in (using .net / c#) Basic idea is I have a List which need to end up as parameters, e.g. List<KeyValuePair<string, object>> ret = new List<KeyValuePair<string, object>>(); ret.Add(new KeyValuePair<string, object>("elem1", true)); ret.Add(new KeyValuePair(string, object>("elem2", false)); Now I want these to show up in string template as: $item.elem1$ $item.elem2$ I can get them to be $elem1$ or $elem2$ but i need them inside of a structure. So I in effect need to convince the string template setAttribute that I'm passing in an object with properties elem1 and elem2 when in fact I have a List of KeyValuePairs. Thanks

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• accessing embedded object with jquery not working in firefox 3.6

  - by taber

  Hi, this code in my plugin used to work just fine: jQuery('#embedded_obj', context).get(0).getVersion(); and in html... <object id="embedded_obj" type="application/x-versionchecker-1.0.0.1"</object Basically trying to get the properties from an embedded object. But it looks like get(0) is returning an html object instead of the actual embedded object. For example, if I do: var launcher = jQuery('#embedded_obj', context).get(0); for(prop in launcher){ alert(prop + ': ' + launcher[prop]); } ... it alerts things like "getElementByNode," "scrollWidth," "clientLeft," "clientTop" etc. Again this worked before Firefox 3.6. Has anyone else seen this or have any ideas/suggestions? Thanks!

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• Traverse list to add elements, C#.

  - by Addie

  I have a list of objects. Each object has an integer quantity and a DateTime variable which contains a month and year value. I'd like to traverse the list and pad the list by adding missing months (with quantity 0) so that all consecutive months are represented in the list. What would be the best way to accomplish this? Example: Original List { Jan10, 3 }, { Feb10, 4 }, { Apr10, 2 }, { May10, 2 }, { Aug10, 3 }, { Sep10, -3 }, { Oct10, 6 }, { Nov10, 3 }, { Dec10, 7 }, { Feb11, 3 } New List { Jan10, 3 }, { Feb10, 4 }, {Mar10, 0}, { Apr10, 2 }, { May10, 2 }, { Jun10, 0 }, { Jul10, 0 } { Aug10, 3 }, { Sep10, -3 }, { Oct10, 6 }, { Nov10, 3 }, { Dec10, 7 }, { Jan11, 0 }, { Feb11, 3 }

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• differences between using wmode="transparent", "opaque", "window" for an embedded object on webpage

  - by Jian Lin

  when embedding a Flash object with the <object and <embed tag, there is an attribute called "wmode". It seems that most of the time, wmode="transparent" is the same as wmode="opaque" as the Flash doesn't actually have any transparent color so that the bottom HTML element is to be shown. As a result, "opaque" should be faster than "transparent" since it require less processing for transparency, yet most of the time i see Flash object embedded with "transparent" instead of "opaque". "opaque" is needed so that other HTML element won't be covered up by the Flash object. (such as a menu item that pops up an extra sub-menu won't be covered up by the Flash object). By the way, is there formal documentation for wmode's "opaque", "transparent", and "window"? I was only able to find blogs that describe it but not the formal documentation. thanks.

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• Scope of object properties & methods

  - by Anish

  In the article Show love to the object literal, it's said: When we have several scripts in a page, the global variables & functions will get overwritten if their name repeats. One solution is to make the variables as properties & functions as methods of an object, and access them via the object name. But will this prevent the issue of variables getting into the global namespace? <script> var movie = { name: "a", trailer: function(){ //code } }; </script> In the above code which elements gets added to the global namespace? a) Just the object name - movie b) Object name as well as the properties and methods inside it – movie, movie.name, movie.trailer()

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• Traverse list to add elements using .NET

  - by Addie

  I have a list of objects. Each object has an integer quantity and a DateTime variable which contains a month and year value. I'd like to traverse the list and pad the list by adding missing months (with quantity 0) so that all consecutive months are represented in the list. What would be the best way to accomplish this? Example: Original List { Jan10, 3 }, { Feb10, 4 }, { Apr10, 2 }, { May10, 2 }, { Aug10, 3 }, { Sep10, -3 }, { Oct10, 6 }, { Nov10, 3 }, { Dec10, 7 }, { Feb11, 3 } New List { Jan10, 3 }, { Feb10, 4 }, {Mar10, 0}, { Apr10, 2 }, { May10, 2 }, { Jun10, 0 }, { Jul10, 0 } { Aug10, 3 }, { Sep10, -3 }, { Oct10, 6 }, { Nov10, 3 }, { Dec10, 7 }, { Jan11, 0 }, { Feb11, 3 }

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• .Remove(object) on a List<T> returned from LINQ to SQL compiled query won't delete the Object right

  - by soldieraman

  I am returning two lists from the database using LINQ to SQL compiled query. While looping the first list I remove duplicates from the second list as I dont want to process already existing objects again. eg. //oldCustomers is a List returned by my Compiled Linq to SQL Statmenet that I have added a .ToList() at the end to //Same goes for newCustomers for (Customer oC in oldCustomers) { //Do some processing newCustomers.Remove(newCusomters.Find(nC=> nC.CustomerID == oC.CusomterID)); } for (Cusomter nC in newCustomers) { //Do some processing } DataContext.SubmitChanges() I expect this to only save the changes that have been made to the customers in my processing and not Remove or Delete any of my customers from the database. Correct? I have tried it and it works fine - but I am trying to know if there is any rare case it might actually get removed

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• slowly rotate an object towards another object

  - by numerical25

  I have an object that points in the direction of another object (i.e. it rotates to the direction that the second objects x and y coordinates are at) below is the code I use. var distx = target.x - x; var disty = target.y - y; var angle:Number = Math.atan2(disty, distx); var vx:Number = Math.cos(angle) * cspeed; var vy:Number = Math.sin(angle) * cspeed; rotation = angle * 180/Math.PI; x += vx; y += vy; as you can see. Not only does it rotate towards the target object, but it also moves towards it too. When I play the movie, the object instantly points to the targeted object and moves towards it. I would like for it to slowly turn towards the object instead of instantly turning towards it. anyone know how to do this.

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• Cannot Translate to SQL using Select(x => Func(x))

  - by Dan

  I'm slowly learning the ins and outs of LINQtoSQL, but this is confusing me. Here is the statement I have: IQueryable<IEvent> events = (from e in db.getEvents() select e).Select(x => SelectEvent(x, null)); What the SelectEvent does can be explained in this answer here. I am not using the .toList() function as I don't want potentially thousands of records brought into memory. public IEvent SelectEvent(SqlServer.Event ev, EventType? type) { // Create an object which implements IEvent // I don't have the code in front of me, so forgive the lack of code } My question is really for the Select() method. I get the "Cannot translate to SQL" error and the Select() is listed in the error message. Clueless on this one :-/.

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