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  • How to detect if a LINQ enumeration is materialized?

    - by Peter Lillevold
    Is there some way of detecting whether an enumerable built using LINQ (to Objects in this case) have been materialized or not? Other than trying to inspect the type of the underlying collection? Specifically, since enumerable.ToArray() will build a new array even if the underlying collection already is an array I'm looking for a way of avoiding ToArray() being called twice on the same collection.

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  • How to use Linq to select and group complex child object from a parents list.

    - by Daoming Yang
    How to use Linq to select and group complex child object from a parents list. 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. My goal is to select and group the most popular products from the order list. Can anyone help me with this? Many thanks.

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  • How to map LINQ EntitySet to List property in property setter?

    - by jlp
    In my model I have these entities: public interface IOrder { string Name {get;set;} List<IProduct> OrderedProducts {get;set;} } public interface IProduct {} In partial class generated by linq-to-sql I map these properties on my entity properties: public partial class Order : IOrder { List<IProduct> OrderedProducts { get { return this.L2SQLProducts.Cast<IProduct>.ToList(); } set { this.L2SQLProducts = ??? } } } How should setter look like?

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  • How can I do a multi level parent-child sort using Linq?

    - by Tenacious T
    How can I do a multi-level parent-child sort using Linq if I have a table structure like the one below: [Table: Sections] Id Seq Name ParentSectionId 1 1 TOP NULL 2 1 AAAA 1 3 2 SSSS 1 4 3 DDDD 1 5 1 SectionA1 2 6 2 SectionA2 2 7 1 SectionS1 3 8 3 ASummary 2 Expected sort result: TOP AAAA SectionA1 SectionA2 ASummary SSSS SectionS1 DDDD

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  • nhibernate activerecord linq Contains problem

    - by Robert Ivanc
    Hi, I am having problems with the following query in Castle ActiveRecord 2.12: var q = from o in SodisceFMClientVAR.Queryable where taxnos2.Contains(o.TaxFileNo) select o; taxNos2 is an array of strings. When run I get an exception: + InnerException {"Index was out of range. Must be non-negative and less than the size of the collection.\r\nParameter name: index"} System.Exception {System.ArgumentOutOfRangeException} StackTrace " at Castle.ActiveRecord.ActiveRecordBase.ExecuteQuery(IActiveRecordQuery query)\r\n at Castle.ActiveRecord.Linq.LinqResultWrapper`1.Populate()\r\n at Castle.ActiveRecord.Linq.LinqResultWrapper`1.GetEnumerator()\r\n at NHibernate.Linq.Query`1.GetEnumerator()\r\n at System.Linq.Buffer`1..ctor(IEnumerable`1 source)\r\n at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)\r\n at prosoft.skb.insolventnostDataAccess.InsolventnostDataAccAR.GetOurUsersListLS(ICollection`1 taxNos) in C:\\svn\\skb\\insolventnostWithAR\\prosoft.skb.insolventnostDataAccess\\InsolventnostDataAR.cs:line 214\r\n at prosoft.skb.insolventnostDataFromWS.InsolventnostFromWS.filterByOurUsers(IEnumerable`1 odprtiPostopki) in C:\\svn\\skb\\insolventnostWithAR\\prosoft.skb.insolventnostDataFromWS\\InsolventnostFromWS.cs:line 237\r\n at prosoft.skb.insolventnostDataFromWS.InsolventnostFromWS.SyncData() in C:\\svn\\skb\\insolventnostWithAR\\prosoft.skb.insolventnostDataFromWS\\InsolventnostFromWS.cs:line 53" string Does Contains even work in linq for nhibernate? I couldn't find anything via google... Is there a workaround? Thanks!

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  • Converting F# Quotations into LINQ Expressions

    - by forki23
    Hi, I can convert a quotation of type Expr<'a -> 'b> to a Linq expression via the following snippet: /// Converts a F# Expression to a LINQ Lambda let toLambda (exp:Expr) = let linq = exp.ToLinqExpression() :?> MethodCallExpression linq.Arguments.[0] :?> LambdaExpression /// Converts a Lambda quotation into a Linq Lamba Expression with 1 parameter let ToLinq (exp : Expr<'a -> 'b>) = let lambda = toLambda exp Expression.Lambda<Func<'a, 'b>>(lambda.Body, lambda.Parameters) Now I want to convert a quotation of type Expr<'a * 'b -> 'c> or maybe even Expr<'a -> 'b -> 'c> to a Linq Lambda Expression of type Expression<Func<'a,'b'c>>. How can I do this? Regards, forki

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  • LINQ Queries And Context

    - by Soo
    Hello SO, I have a slight issue with some code I'm writing if(parameter == 1) { var linq = from a in db.table select a; } else { var linq = from a in db.table where a.id = 1 select a; } foreach(var b in linq) { ... } So basically what's going on is that the variable "linq" is different depending on the value of "parameter". When I try to loop through "linq" with my foreach loop, I get an error about how linq doesn't exist in the current context. What is the best way to work around this type of issue?

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  • Does LINQ require significantly more processing cycles and memory than lower-level data iteration techniques?

    - by Matthew Patrick Cashatt
    Background I am recently in the process of enduring grueling tech interviews for positions that use the .NET stack, some of which include silly questions like this one, and some questions that are more valid. I recently came across an issue that may be valid but I want to check with the community here to be sure. When asked by an interviewer how I would count the frequency of words in a text document and rank the results, I answered that I would Use a stream object put the text file in memory as a string. Split the string into an array on spaces while ignoring punctuation. Use LINQ against the array to .GroupBy() and .Count(), then OrderBy() said count. I got this answer wrong for two reasons: Streaming an entire text file into memory could be disasterous. What if it was an entire encyclopedia? Instead I should stream one block at a time and begin building a hash table. LINQ is too expensive and requires too many processing cycles. I should have built a hash table instead and, for each iteration, only added a word to the hash table if it didn't otherwise exist and then increment it's count. The first reason seems, well, reasonable. But the second gives me more pause. I thought that one of the selling points of LINQ is that it simply abstracts away lower-level operations like hash tables but that, under the veil, it is still the same implementation. Question Aside from a few additional processing cycles to call any abstracted methods, does LINQ require significantly more processing cycles to accomplish a given data iteration task than a lower-level task (such as building a hash table) would?

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  • LINQ 4 XML - What is the proper way to query deep in the tree structure?

    - by Keith Barrows
    I have an XML structure that is 4 deep: <?xml version="1.0" encoding="utf-8"?> <EmailRuleList xmlns:xsd="EmailRules.xsd"> <TargetPST name="Tech Communities"> <Parse emailAsList="true" useJustDomain="false" fromAddress="false" toAddress="true"> <EmailRule address="@aspadvice.com" folder="Lists, ASP" saveAttachments="false" /> <EmailRule address="@sqladvice.com" folder="Lists, SQL" saveAttachments="false" /> <EmailRule address="@xmladvice.com" folder="Lists, XML" saveAttachments="false" /> </Parse> <Parse emailAsList="false" useJustDomain="false" fromAddress="false" toAddress="true"> <EmailRule address="[email protected]" folder="Special Interest Groups|Northern Colorado Architects Group" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Support|SpamBayes" saveAttachments="false" /> </Parse> <Parse emailAsList="false" useJustDomain="false" fromAddress="true" toAddress="false"> <EmailRule address="[email protected]" folder="Support|GoDaddy" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Support|No-IP.com" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Discussions|Orchard Project" saveAttachments="false" /> </Parse> <Parse emailAsList="false" useJustDomain="true" fromAddress="true" toAddress="false"> <EmailRule address="@agilejournal.com" folder="Newsletters|Agile Journal" saveAttachments="false"/> <EmailRule address="@axosoft.ccsend.com" folder="Newsletters|Axosoft Newsletter" saveAttachments="false"/> <EmailRule address="@axosoft.com" folder="Newsletters|Axosoft Newsletter" saveAttachments="false"/> <EmailRule address="@cmcrossroads.com" folder="Newsletters|CM Crossroads" saveAttachments="false" /> <EmailRule address="@urbancode.com" folder="Newsletters|Urbancode" saveAttachments="false" /> <EmailRule address="@urbancode.ccsend.com" folder="Newsletters|Urbancode" saveAttachments="false" /> <EmailRule address="@Infragistics.com" folder="Newsletters|Infragistics" saveAttachments="false" /> <EmailRule address="@zdnet.online.com" folder="Newsletters|ZDNet Tech Update Today" saveAttachments="false" /> <EmailRule address="@sqlservercentral.com" folder="Newsletters|SQLServerCentral.com" saveAttachments="false" /> <EmailRule address="@simple-talk.com" folder="Newsletters|Simple-Talk Newsletter" saveAttachments="false" /> </Parse> </TargetPST> <TargetPST name="[Sharpen the Saw]"> <Parse emailAsList="false" useJustDomain="false" fromAddress="false" toAddress="true"> <EmailRule address="[email protected]" folder="Head Geek|Job Alerts" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Social|LinkedIn USMC" saveAttachments="false"/> </Parse> <Parse emailAsList="false" useJustDomain="false" fromAddress="true" toAddress="false"> <EmailRule address="[email protected]" folder="Head Geek|Job Alerts" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Head Geek|Job Alerts" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Social|Cruise Critic" saveAttachments="false"/> </Parse> <Parse emailAsList="false" useJustDomain="true" fromAddress="true" toAddress="false"> <EmailRule address="@moody.edu" folder="Social|5 Love Languages" saveAttachments="false" /> <EmailRule address="@postmaster.twitter.com" folder="Social|Twitter" saveAttachments="false"/> <EmailRule address="@diabetes.org" folder="Physical|American Diabetes Association" saveAttachments="false"/> <EmailRule address="@membership.webshots.com" folder="Social|Webshots" saveAttachments="false"/> </Parse> </TargetPST> </EmailRuleList> Now, I have both an FromAddress and a ToAddress that is parsed from an incoming email. I would like to do a LINQ query against a class set that was deserialized from this XML. For instance: ToAddress = [email protected] FromAddress = [email protected] Query: Get EmailRule.Include(Parse).Include(TargetPST) where address == ToAddress AND Parse.ToAddress==true AND Parse.useJustDomain==false Get EmailRule.Include(Parse).Include(TargetPST) where address == [ToAddress Domain Only] AND Parse.ToAddress==true AND Parse.useJustDomain==true Get EmailRule.Include(Parse).Include(TargetPST) where address == FromAddress AND Parse.FromAddress==true AND Parse.useJustDomain==false Get EmailRule.Include(Parse).Include(TargetPST) where address == [FromAddress Domain Only] AND Parse.FromAddress==true AND Parse.useJustDomain==true I am having a hard time figuring this LINQ query out. I can, of course, loop on all the bits in the XML like so (includes deserialization into objects): XmlSerializer s = new XmlSerializer(typeof(EmailRuleList)); TextReader r = new StreamReader(path); _emailRuleList = (EmailRuleList)s.Deserialize(r); TargetPST[] PSTList = _emailRuleList.Items; foreach (TargetPST targetPST in PSTList) { olRoot = GetRootFolder(targetPST.name); if (olRoot != null) { Parse[] ParseList = targetPST.Items; foreach (Parse parseRules in ParseList) { EmailRule[] EmailRuleList = parseRules.Items; foreach (EmailRule targetFolders in EmailRuleList) { } } } } However, this means going through all these loops for each and every address. It makes more sense to me to query against the Objects. Any tips appreciated!

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  • linq query - The method or operation is not implemented.

    - by Dejan.S
    I'm doing the Rob Conery mvc storefront and at one place I'm suppose to get categories but I get an error with this linq query and I can not get why. It's exactly the same as his. var culturedName = from ct in ReadOnlyContext.CategoryCultureDetails where ct.Culture.LanguageCode == System.Globalization.CultureInfo.CurrentUICulture.TwoLetterISOLanguageName select new { ct.CategoryName, ct.CategoryId }; return from c in ReadOnlyContext.Categories join cn in culturedName on c.CategoryId equals cn.CategoryId select new Core.Model.Category { Id = c.CategoryId, Name = cn.CategoryName, ParentId = c.ParentId ?? 0, Products = new LazyList<Core.Model.Product>(from p in GetProducts() join cp in ReadOnlyContext.Categories_Products on p.Id equals cp.ProductId where cp.CategoryId == c.CategoryId select p) }; its the return query that mess things up. I have checked and the culturename actually gets data from the database. Appricate your help

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  • ASP.NET MVC <OutputCache> SqlDependency (CommandNotification?) with LINQ queries

    - by sinni800
    Hello, I use LINQ queries in my ASP.NET MVC application and want to use OutputCache in some of my Actions. I hear this should be possible with CommandNotifications. But those seem to only go for self-created SQLCommands, or am I wrong? Can I manually tell SQL server to send SQLDependency notifications if certain tables change? And if yes, how can I attach them to the OutputCache? Another side question: Can you do this with strongly types views too? Thank you in advance...

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  • How dynamic can I make my LINQ To SQL Statements?

    - by mcass20
    I have the need to construct a LINQ To SQL statement at runtime based on input from a user and I can't seem to figure out how to dynamically build the WHERE clause. I have no problem with the following: string Filters = "<value>FOO</value>"; Where("FormattedMessage.Contains(@0)",Filters) But what I really need is to make the entire WHERE clause dynamic. This way I can add multiple conditions at runtime like this (rough idea): foreach (Filter filter in filterlist) { whereclause = whereclause + "&& formattedmessage.contains(filter)"; }

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  • Using LINQ to XML, how can I join two sets of data based on ordinal position?

    - by Donald Hughes
    Using LINQ to XML, how can I join two sets of data based on ordinal position? <document> <set1> <value>A</value> <value>B</value> <value>C</value> </set1> <set2> <value>1</value> <value>2</value> <value>3</value> </set2> </document> Based on the above fragment, I would like to join the two sets together such that "A" and "1" are in the same record, "B" and "2" are in the same record, and "C" and "3" are in the same record.

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  • linq to xml. read. and assign to ViewData..noob

    - by raklos
    I have some xml similar to this: <?xml version="1.0" encoding="utf-8" ?> <data> <resources> <resource key="Title">Alpha</resource> <resource key="ImageName">Small.png</resource> <resource key="Desc">blah</resource> </resources> </data> using linq-xml how can i assign each resource here as a key value pair with the ViewData collection. Thanks.

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  • How to get List of results from list of ID values with LINQ to SQL?

    - by DaveDev
    I have a list of ID values: List<int> MyIDs { get; set; } I'd like to pass this list to an interface to my repository and have it return a List that match the ID values I pass in. List<MyType> myTypes = new List<MyType>(); IMyRepository myRepos = new SqlMyRepository(); myTypes = myRepos.GetMyTypes(this.MyIDs); Currently, GetMyTypes() behaves similarly to this: public MyType GetMyTypes(int id) { return (from myType in db.MyTypes where myType.Id == id select new MyType { MyValue = myType.MyValue }).FirstOrDefault(); } where I iterate through MyIDs and pass each id in and add each result to a list. How do I need to change the LINQ so that I can pass in the full list of MyIDs and get a list of MyTypes out? GetMyTypes() would have a signature similar to public List<MyType> GetMyTypes(List<int> myIds)

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  • LINQ-to-XML to DataGridView: Cannot edit fields -- How to fix?

    - by Pretzel
    I am currently doing LINQ-to-XML and populating a DataGridView with my query just fine. The trouble I am running into is that once loaded into the DataGridView, the values appear to be Un-editable (ReadOnly). Here's my code: var barcodes = (from src in xmldoc.Descendants("Container") where src.Descendants().Count() > 0 select new { Id = (string)src.Element("Id"), Barcode = (string)src.Element("Barcode"), Quantity = float.Parse((string)src.Element("Quantity").Attribute("value")) }).Distinct(); dataGridView1.DataSource = barcodes.ToList(); I read somewhere that the "DataGridView will be in ReadOnly mode when you use Anonymous types." But I couldn't find an explanation why or exactly what to do about it. Any ideas?

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  • Extending LINQ classes to my own partial classes in different namespaces?

    - by sah302
    I have a .dbml file which of course contains the auto-generated classes based on my tables. I would however, like to extend them to my own classes. Typically I design such that each of my tables get their own namespace in their own folder containing all of their associated dao and service classes. So if I am dealing with a page that only has to do with 'customers' for instance, I can only include the customerNS. But when using LINQ I seem to be unable to do this. I have tried removing a default namespace from the project, I have tried putting the .dbml file into it's own folder with a custom namespace and then adding a 'using' statement, but no nothing works. I also saw the Entity Namespace, Context Namespace, and Custom Tool Namespace properties associated with the .dbml file and tried setting all these to names x and trying 'using x' in my other class to allow me to extend partial classes, but it just doesn't work. Is this possible or do I have to keep all extended partial classes in the same namespace as the .dbml file?

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  • How can I use linq to build an object from 1 row of data?

    - by Hcabnettek
    Hi All, I have a quick linq question. I have a stored proc that should return one row of data. I would like to use a lambda to build an object. Here's what I'm currently doing which works, but I know I should be able to use First instead of Select except I can't seem to get the syntax correct. Can anyone straighten me out here? Thanks for any help. var location = new GeoLocationDC(); DataSet ds = db.ExecuteDataSet(dbCommand); if(ds.Tables[0].Rows.Count == 1) { var rows = ds.Tables[0].AsEnumerable(); var x = rows.Select( c => new GeoLocationDC { Latitude = Convert.ToInt32(c.Field<string>("LATITUDE")), Longitude = Convert.ToInt32(c.Field<string>("LONGITUDE")) }).ToList(); if(x.Count > 0 ) { location = x[0]; } Cheers, ~ck }

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  • LINQ to SQL for tables across databases. Or View?

    - by BritishDeveloper
    I have a Message table and a User table. Both are in separate databases. There is a userID in the Message table that is used to join to the User table to find things like userName. How can I create this in LINQ to SQL? I can't seem to do a cross database join. Should I create a View in the database and use that instead? Will that work? What will happen to CRUD against it? E.g. if I delete a message - surely it won't delete the user? I'd imagine it would throw an error. What to do? I can't move the tables into the same database!

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  • Using Linq, how to separate a list in to grouped objects by name?

    - by Dr. Zim
    I have a table where a record looks like this varchar(255) Name varchar(255) Text varchar(255) Value Name is the DDL name, Text is what is displayed, and Value is returned upon selection. There are between one and twenty options for each Name. Without iterating though each option like a cursor, is there any way to pull out a list of objects, one for each unique DDL Name, using Linq and C#? A sample of the data: Beds '4 (10)' 4 Beds '5 (1)' 5 Beds '7 (1)' 7 Baths 'NA (13)' NULL Baths '0 (1)' 0 Baths '1 (13)' 1 I was thinking about doing an outer select to get the unique Names, then an inner select to get the list of options for it, then return the set as a List of a set of Lists.

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  • How can I use external expressions in Linq with EF4 (and LINQKit)?

    - by neo
    I want to separate out often used expressions in linq queries. I'm using Entity Framework 4 and also LINQKit but I still don't know how I should do it the right way. Let me give you an example: Article article = dataContainer.Articles.FirstOrDefault(a => a.Id == id); IEnumerable<Comment> comments = (from c in container.Comments where CommentExpressions.IsApproved.Invoke(c) select c); public static class CommentExpressions { public static Expression<Func<Module, bool>> IsApproved { get { return m => m.IsApproved; } } } Of course the IsApproved expression would be something much more complicated. The problem is that the Invoke() won't work because I didn't call .asExpandable() from LINQKit on container.Comments but I can't call it because it's just an ICollection instead of an ObjectSet. So my question is: Do I always have to go through the data context when I want to include external expressions or can I somehow use it on the object I fetched (Article)? Any ideas or best practices? Thanks very much! neo

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