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  • Can someone please explain this lazy evaluation code?

    - by Tejs
    So, this question was just asked on SO: http://stackoverflow.com/questions/2740001/how-to-handle-an-infinite-ienumerable My sample code: public static void Main(string[] args) { foreach (var item in Numbers().Take(10)) Console.WriteLine(item); Console.ReadKey(); } public static IEnumerable<int> Numbers() { int x = 0; while (true) yield return x++; } Can someone please explain why this is lazy evaluated? I've looked up this code in Reflector, and I'm more confused than when I began. Reflector outputs: public static IEnumerable<int> Numbers() { return new <Numbers>d__0(-2); } For the numbers method, and looks to have generated a new type for that expression: [DebuggerHidden] public <Numbers>d__0(int <>1__state) { this.<>1__state = <>1__state; this.<>l__initialThreadId = Thread.CurrentThread.ManagedThreadId; } This makes no sense to me. I would have assumed it was an infinite loop until I put that code together and executed it myself.

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  • Sorting Anonymous Types

    - by strobaek
    I have a question of how to sort an anonymous type. Using Linq2SQL I have the following query, which returns a list of submissions: var submissions = EventSubmissions .Where(s => s.EventId.Equals(eventId)); Consider the following interface (somewhat simplyfied): public interface IQuerySorter { IOrderedQueryable Sort(IQueryable query); IOrderedQueryable<T> Sort<T, U>(IQueryable<T> query, Expression<Func<T,U>> selector); ... } Using this interface allows me to implement a number of 'sorters', e.g. on Date, Rating or whether or not a submission has been nominated (for voting). sortedQuery = sorter.Sort(submissions) So far so good. A submission can be made "votable". I get the number of votes a nominated submission may have using the following query: var withVoteCount = submissions .Select(s => new {NumberOfVotes = s.Votes.Count(), Submission = s}); I would like to sort this new query by NumberOfVotes using my "general" sorter class, but run into the problem that the anonymous type/member does not seem to live outside the repository-method, hence I am unable to sort on it. Any input would be greatly appreciated.

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  • Equality between two enumerables

    - by Berryl
    I have two enumerables with the exact same reference elements, and wondering why Equals wouldn't be true. As a side question, the code below to compare each element works, but there must be a more elegant way Cheers, Berryl var other = (ActivityService) obj; if (!AllAccounts.Count().Equals(other.AllAccounts.Count())) return false; for (int i = 0; i < AllAccounts.Count(); i++) { if (!AllAccounts.ElementAt(i).Equals(other.AllAccounts.ElementAt(i))) { return false; } } return true;

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  • Build and render infinite hierarchical category tree from self-referential category table

    - by FreshCode
    I have a Categories table in which each category has a ParentId that can refer to any other category's CategoryId that I want to display as multi-level HTML list, like so: <ul class="tree"> <li>Parent Category <ul> <li>1st Child Category <!-- more sub-categories --> </li> <li>2nd Child Category <!-- more sub-categories --> </li> </ul> </li> </ul> Presently I am recursively rendering a partial view and passing down the next category. It works great, but it's wrong because I'm executing queries in a view. How can I render the list into a tree object and cache it for quick display every time I need a list of all hierarchical categories?

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  • How can I write a clean Repository without exposing IQueryable to the rest of my application?

    - by Simucal
    So, I've read all the Q&A's here on SO regarding the subject of whether or not to expose IQueryable to the rest of your project or not (see here, and here), and I've ultimately decided that I don't want to expose IQueryable to anything but my Model. Because IQueryable is tied to certain persistence implementations I don't like the idea of locking myself into this. Similarly, I'm not sure how good I feel about classes further down the call chain modifying the actual query that aren't in the repository. So, does anyone have any suggestions for how to write a clean and concise Repository without doing this? One problem I see, is my Repository will blow up from a ton of methods for various things I need to filter my query off of. Having a bunch of: IEnumerable GetProductsSinceDate(DateTime date); IEnumberable GetProductsByName(string name); IEnumberable GetProductsByID(int ID); If I was allowing IQueryable to be passed around I could easily have a generic repository that looked like: public interface IRepository<T> where T : class { T GetById(int id); IQueryable<T> GetAll(); void InsertOnSubmit(T entity); void DeleteOnSubmit(T entity); void SubmitChanges(); } However, if you aren't using IQueryable then methods like GetAll() aren't really practical since lazy evaluation won't be taking place down the line. I don't want to return 10,000 records only to use 10 of them later. What is the answer here? In Conery's MVC Storefront he created another layer called the "Service" layer which received IQueryable results from the respository and was responsible for applying various filters. Is this what I should do, or something similar? Have my repository return IQueryable but restrict access to it by hiding it behind a bunch of filter classes like GetProductByName, which will return a concrete type like IList or IEnumerable?

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  • Switching from LinqToXYZ to LinqToObjects

    - by spender
    In answering this question, it got me thinking... I often use this pattern: collectionofsomestuff //here it's LinqToEntities .Select(something=>new{something.Name,something.SomeGuid}) .ToArray() //From here on it's LinqToObjects .Select(s=>new SelectListItem() { Text = s.Name, Value = s.SomeGuid.ToString(), Selected = false }) Perhaps I'd split it over a couple of lines, but essentially, at the ToArray point, I'm effectively enumerating my query and storing the resulting sequence so that I can further process it with all the goodness of a full CLR to hand. As I have no interest in any kind of manipulation of the intermediate list, I use ToArray over ToList as there's less overhead. I do this all the time, but I wonder if there is a better pattern for this kind of problem?

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  • ASP.NET MVC pagination problem????

    - by MD_Oppenheimer
    OK, This is starting to get mildly irritating. I tried to implement Twitter style paging using ASP.NET MVC and JQuery my problem is that when not using Request.IsAjaxRequest() (for users with javascript turned off) it works fine, obviously posting back the whole page. when I run the code for Request.IsAjaxRequest(), it skips entries, and does not return result in order. this is the code I have: public ActionResult Index(int? startRow) { StatusUpdatesRepository statusUpdatesRepository = new StatusUpdatesRepository(); if (!startRow.HasValue) startRow = Globals.Settings.StatusUpdatesSection.StatusUpdateCount;//5 Default starting row //Retrieve the first page with a page size of entryCount int totalItems; if (Request.IsAjaxRequest()) { IEnumerable<StatusUpdate> PagedEntries = statusUpdatesRepository.GetLastStatusUpdates(startRow.Value,Globals.Settings.StatusUpdatesSection.StatusUpdateCount, out totalItems); if (startRow < totalItems) AddMoreUrlToViewData(startRow.Value); return View("StatusUpdates", PagedEntries); } //Retrieve the first page with a page size of global setting // First run skip 0 take 5 IEnumerable<StatusUpdate> entries = statusUpdatesRepository.GetLastStatusUpdates(0,startRow.Value, out totalItems); if (startRow < totalItems) AddMoreUrlToViewData(startRow.Value); return View(entries); } private void AddMoreUrlToViewData(int entryCount) { ViewData["moreUrl"] = Url.Action("Index", "Home", new { startRow = entryCount + Globals.Settings.StatusUpdatesSection.StatusUpdateCount }); } My GetLastStatusUpdates function: public IQueryable GetLastStatusUpdates(int startRowIndex, int maximumRows,out int statusUpdatesCount ) { statusUpdatesCount = db.StatusUpdates.Count(); return db.StatusUpdates .Skip(startRowIndex) .Take(maximumRows) .OrderByDescending(s = s.AddedDate); } Really fresh out out of ideas as to why this is not working properly when responding to a Request.IsAjaxRequest(), ie when I turn of javascript in the browser, the code works perfectly, except I don't want to repost the whole page????

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  • Gridview buttonfield works LinkButton doesn't

    - by Karsten
    I've been fighting this problem for many hours now and could really use some help :-) This is the grid <asp:GridView ID="annonceView" runat="server" AutoGenerateColumns="False" DataKeyNames="Id" DataSourceID="dataSourceAnnoncer"> <Columns> <asp:BoundField DataField="Productname" HeaderText="Productname" /> <asp:buttonfield buttontype="Link" commandname="Delete" text="Delete"/> <asp:TemplateField HeaderText="Administration"> <ItemTemplate> <asp:LinkButton ID="lnkBtnDelete" runat="server" Text="Delete" CausesValidation="False" CommandName="Delete" OnClientClick="return confirm('Delete?')" /> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> <asp:LinqDataSource ID="dataSourceAnnoncer" runat="server" ContextTypeName="Namespcae.TheContext" EnableDelete="True" TableName="Annoncer"> </asp:LinqDataSource> Clicking the buttonfield deletes the record just fine. Clicking the LinkButton doesn't work. I get a postback and the grid is shown as empty and no record is deleted. Seems like an empty databinding. I have tried to create a custom OnClick, OnCommand event for the LinkButton, but neither are fired. The OnRowCommand isn't fired either. I don't manually DataBind in the codebehind.

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  • How do I eliminate Error 3002?

    - by Andrew
    Say I have the following table definitions in SQL Server 2008: CREATE TABLE Person (PersonId INT IDENTITY NOT NULL PRIMARY KEY, Name VARCHAR(50) NOT NULL, ManyMoreIrrelevantColumns VARCHAR(MAX) NOT NULL) CREATE TABLE Model (ModelId INT IDENTITY NOT NULL PRIMARY KEY, ModelName VARCHAR(50) NOT NULL, Description VARCHAR(200) NULL) CREATE TABLE ModelScore (ModelId INT NOT NULL REFERENCES Model (ModelId), Score INT NOT NULL, Definition VARCHAR(100) NULL, PRIMARY KEY (ModelId, Score)) CREATE TABLE PersonModelScore (PersonId INT NOT NULL REFERENCES Person (PersonId), ModelId INT NOT NULL, Score INT NOT NULL, PRIMARY KEY (PersonId, ModelId), FOREIGN KEY (ModelId, Score) REFERENCES ModelScore (ModelId, Score)) The idea here is that each Person may have only one ModelScore per Model, but each Person may have a score for any number of defined Models. As far as I can tell, this SQL should enforce these constraints naturally. The ModelScore has a particular "meaning," which is contained in the Definition. Nothing earth-shattering there. Now, I try translating this into Entity Framework using the designer. After updating the model from the database and doing some editing, I have a Person object, a Model object, and a ModelScore object. PersonModelScore, being a join table, is not an object but rather is included as an association with some other name (let's say ModelScorePersonAssociation). The mapping details for the association are as follows: - Association - Maps to PersonModelScore - ModelScore ModelId : Int32 <=> ModelId : int Score : Int32 <=> Score : int - Person PersonId : Int32 <=> PersonId : int On the right-hand side, the ModelId and PersonId values have primary key symbols, but the Score value does not. Upon compilation, I get: Error 3002: Problem in Mapping Fragment starting at line 5190: Potential runtime violation of table PersonModelScore's keys (PersonModelScore.ModelId, PersonModelScore.PersonId): Columns (PersonModelScore.PersonId, PersonModelScore.ModelId) are mapped to EntitySet ModelScorePersonAssociation's properties (ModelScorePersonAssociation.Person.PersonId, ModelScorePersonAssociation.ModelScore.ModelId) on the conceptual side but they do not form the EntitySet's key properties (ModelScorePersonAssociation.ModelScore.ModelId, ModelScorePersonAssociation.ModelScore.Score, ModelScorePersonAssociation.Person.PersonId). What have I done wrong in the designer or otherwise, and how can I fix the error? Many thanks!

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  • Getting "<kml:..." everywhere, updating a Kml file

    - by Rafe Lavelle
    I'm reading in a Kml file, changing the placemarks' names, and saving it again. var KmlFile = XDocument.Load("C:\\Inetpub\\wwwroot\\GeotagService\\Kml\\Photographs.kml"); XNamespace KmlNamespace = "http://www.opengis.net/kml/2.2"; // find the Placemarks in the Photos folder IEnumerable<XElement> Placemarks = KmlFile.Element(KmlNamespace + "kml").Element(KmlNamespace + "Document").Element(KmlNamespace + "Folder").Elements(KmlNamespace + "Placemark"); foreach (XElement p in Placemarks){ p.Element(KmlNamespace + "name").Value = "testing"; } KmlFile.Save("C:\\Inetpub\\wwwroot\\GeotagService\\Kml\\Photographs.kml"); When I save it however, every element is prefixed with <kml:, like this: <kml:Folder> <kml:name>Photos</kml:name> <kml:open>1</kml:open> <kml:Placemark> <kml:name>testing</kml:name> <kml:LookAt> <kml:longitude>-10.02717694938161</kml:longitude> <kml:latitude>53.48672543547379</kml:latitude> <kml:altitude>0</kml:altitude> </kml:LookAt> <kml:styleUrl>#msn_ylw-pushpin1</kml:styleUrl> <kml:Point> <kml:coordinates>-10.02867619360582,53.48651240326751,0</kml:coordinates> </kml:Point> </kml:Placemark>... Tomalak's comment on this question about blank xmlns gives me a clue that it might be inconsistencies between the namespaces of the document and the elements, but I can't see how I'm doing that. Anyone know?

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  • Conditional OrderBy

    - by jeriley
    So, right now I've got a number of columns the user can sort by (Name, County, Active) and that's easy but messy. Looks something like this... Select Case e.SortExpression Case "Name" If (isDescending) Then resultsList.OrderByDescending(Function(a) a.Name).ToList() Else resultsList.OrderBy(Function(a) a.Name).ToList() End If Case "County" ... and so on what I would LIKE to do, is something more ... graceful, like this Private Function SortThatList(ByVal listOfStuff As List(Of Stuff), ByVal isDescending As Boolean, ByVal expression As Func(Of Stuff)) As List(Of Stuff) If (isDescending) Then Return listOfStuff.OrderByDescending(expression) Else : Return listOfStuff.OrderBy(expression) End If End Function but it doesn't like the datatype (Of TKey) ... I've tired Func(Of stuff, boolean) (got something in c# that works nicely like that) but can't seem to get this one to do what I want. Ideas? What's the magic syntax?

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  • how to use Foreign key in L2E or EF?

    - by 5YrsLaterDBA
    I have a User table which has a PrivilegeId foreign key points to a Privilege table and is the primary key there. In Entity Framework, the VS will not generate a PrivilegeId variable under Users for you. It will generate a Privilege property and PrivilegeReference property for you instead. When I load a User, the Privilege property is null by default. That means EF does not load refered entity for you automatically. I think I may did something wrong? I cannot load Privilege separatedly because I have no info about the Privilege at that time. I guess EF should load the refered entities for me but I missed something. anybody can help me?

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  • Using an existing IQueryable to create a new dynamic IQueryable

    - by dnoxs
    I have a query as follows: var query = from x in context.Employees where (x.Salary > 0 && x.DeptId == 5) || x.DeptId == 2 order by x.Surname select x; The above is the original query and returns let's say 1000 employee entities. I would now like to use the first query to deconstruct it and recreate a new query that would look like this: var query = from x in context.Employees where ((x.Salary > 0 && x.DeptId == 5) || x.DeptId == 2) && (x,i) i % 10 == 0 order by x.Surname select x.Surname; This query would return 100 surnames. The syntax is probably incorrect, but what I need to do is attach an additional where clause and modify the select to a single field. I've been looking into the ExpressionVisitor but I'm not entirely sure how to create a new query based on an existing query. Any guidance would be appreciated. Thanks you.

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  • XML to Type - Quick way?

    - by MRFerocius
    Team; How are you doing? Im breaking my head trying to do this that seems simple but I can't figure it out... Suppose I have this XML as a string: <calles> <calle> <nombre>CALLAO AV.</nombre> <altura>1500</altura> <longitud>-58.3918617027</longitud> <latitud>-34.5916734896</latitud> <barrio>Recoleta</barrio> </calle> </calles> And and have this Type I created to map that XML: public class Ubicacion { public string Latitud { get; set; } public string Longitud { get; set; } public string Nombre { get; set; } public string Altura { get; set; } public string Barrio { get; set; } public Ubicacion() { } } I need to take that XML file and create an object with those values... Does somebody know a quick way to do it? with C#? I have been trying this but is not working at all... XElement dir = XElement.Parse(text); Ubicacion informacion = from d in dir.Elements("calle"). select new Ubicacion { Longitud = d.Element("longitud").Value, Latitud = d.Element("latitud").Value, Altura = d.Element("altura").Value, Nombre = d.Element("nombre").Value, Barrio = d.Element("barrio").Value, }; return informacion.Cast<Ubicacion>(); } Any ideas? Thanks!!!

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  • Expression Tree Binary Expression for an 'In' operation

    - by Adam Driscoll
    I'm trying to build an expression tree (still) but getting further! I need to create a BinaryExpression to perform an 'In' comparison between a Member and a collection of items. Hence, the expression should return true if the member is contained within the items. This obviously does not exist: Expression.MakeBinary(ExpressionType.In, memberExpression, constantExpression); constantExpression is a ConstantExpression of type IEnumerable while memberExpression is a MemberExpression of type T. How would I create such an expression?

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  • Settings variable values in a Moq Callback() call

    - by Adam Driscoll
    I think I may be a bit confused on the syntax of the Moq Callback methods. When I try to do something like this: IFilter filter = new Filter(); List<IFoo> objects = new List<IFoo> { new Foo(), new Foo() }; IQueryable myFilteredFoos = null; mockObject.Setup(m => m.GetByFilter(It.IsAny<IFilter>())).Callback( (IFilter filter) => myFilteredFoos = filter.FilterCollection(objects)).Returns(myFilteredFoos.Cast<IFooBar>()); This throws a exception because myFilteredFoos is null during the Cast<IFooBar>() call. Is this not working as I expect? I would think FilterCollection would be called and then myFilteredFoos would be non-null and allow for the cast. FilterCollection is not capable of returning a null which draws me to the conclusion it is not being called. Also, when I declare myFilteredFoos like this: Queryable myFilteredFoos; The Return call complains that myFilteredFoos may be used before it is initialized.

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  • Removing table prefixes on ASP.NET MVC DataModel entities

    - by Tim Shults
    My database tables have prefixes on them and when the DataModel generates the EntityObjects they have the prefixes at the beginning of the class name. Is there anyway that I can have those prefixes ignored when the DataModel is updating/creating the classes? I've found the below question, but with no solution. http://stackoverflow.com/questions/1800065/removing-table-prefix-in-linq2sql-setup/2525827#2525827 Thanks in advance, Tim Shults

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  • How can I combine several Expressions into a fast method?

    - by chillitom
    Suppose I have the following expressions: Expression<Action<T, StringBuilder>> expr1 = (t, sb) => sb.Append(t.Name); Expression<Action<T, StringBuilder>> expr2 = (t, sb) => sb.Append(", "); Expression<Action<T, StringBuilder>> expr3 = (t, sb) => sb.Append(t.Description); I'd like to be able to compile these into a method/delegate equivalent to the following: void Method(T t, StringBuilder sb) { sb.Append(t.Name); sb.Append(", "); sb.Append(t.Description); } What is the best way to approach this? I'd like it to perform well, ideally with performance equivalent to the above method. UPDATE So, whilst it appears that there is no way to do this directly in C#3 is there a way to convert an expression to IL so that I can use it with System.Reflection.Emit?

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  • XElement Path Validation

    - by cw
    Hello, I am trying to validate Elements and Attributes exist in an XElement. Basically, I was wondering if anyone had a generic way to check if a give path is null. I don't have access to System.Xml.XPath (doing this for compact framework). Basically what I have is: <root value"1000"> <element1>test<element1> <element2>1<element2> .... <element30> <subElement1>stuff</subElement1> </element30> </root> Now I know you can "if this is null do this and that". But since there is upwards of 30 elements that can be under root, which are optional elements, I need a way to grab the value if it exists and convert it to the correct type (which I know) in a nice compact way. Any suggestions?

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  • How to avoid "The name 'ConfigurationManager' does not exist in the current context" error?

    - by 5YrsLaterDBA
    I am using VS2008. I have a project connect with a database and the connection string is read from App.config via ConfigurationManager. We are using L2E. Now I added a helper project, AndeDataViewer, to have a simple UI to display data from the database for testing/verification purpose. I don't want to create another set of Entity Data Model in the helper project. I just added all related files as a link in the new helper project. When I compile, I got the following error: Error 15 The name 'ConfigurationManager' does not exist in the current context C:\workspace\SystemSoftware\SystemSoftware\src\systeminfo\RuntimeInfo.cs 24 40 AndeDataViewer I think I may need to add another project setting/config related file's link to the helper project from the main project? There is no App.config file in the new helper project. But it looks I cannot add that file's link to the helper project. Any ideas?

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  • Linq2XML not getting content of a node that contains html tags

    - by Dante
    Hi, I have an XML file that I'm trying to parse with Linq2XML. One of the nodes contains a bit of html, that I cannot retrieve. The XML resembles to: <?xml version="1.0" encoding="ISO-8859-1"?> <root> <image><img src="/Images/m1cznk4a6fh7.jpg" /></image> <contentType>Banner</contentType> </root> The code is: XDocument document = XDocument.Parse(content.XML); XElement imageElement = document.Descendants("image").SingleOrDefault(); image = imageElement.Value; // Doesn't get the content, while if I specify .Descendants("contentType") it works Any ideas? Thank you in advance

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  • Add WhereParameters to LinqDataSource in Selecting event

    - by Steven
    I have a repeater using a LinqDataSource as a data source. When a query string is entered, I'd like to filter the results, but ONLY when a query string is entered. If there is no query string, the results should not be filtered, all results should be returned. I'm trying to add a WhereParameter to my LinqDataSource in the Selecting event of the LinqDataSource, but it's not working. Here's my code: protected void ldsImages_Selecting(object sender, LinqDataSourceSelectEventArgs e) { if (Request.QueryString["id"] != null) { e.WhereParameters.Add("ImageTypeID", Request.QueryString["id"]); } }

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