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  • How do I transfer this logic into a LINQ statement?

    - by Geoffrey
    I can't get this bit of logic converted into a Linq statement and it is driving me nuts. I have a list of items that have a category and a createdondate field. I want to group by the category and only return items that have the max date for their category. So for example, the list contains items with categories 1 and 2. The first day (1/1) I post two items to both categories 1 and 2. The second day (1/2) I post three items to category 1. The list should return the second day postings to category 1 and the first day postings to category 2. Right now I have it grouping by the category then running through a foreach loop to compare each item in the group with the max date of the group, if the date is less than the max date it removes the item. There's got to be a way to take the loop out, but I haven't figured it out!

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  • LINQ and paging with a DataTable - can't get Skip working?

    - by Kit Menke
    Ok so this might be a dumb question, but I can't seem to figure it out. I thought I'd try out LINQ against a DataTable. I got my query working and now I'm trying to implement some simple paging. DataTable dataTable = null; dataTable = GetAllDataTables(); var query = from r in dataTable.AsEnumerable() orderby r.Field<string>(Constants.fileName) select r; query.Skip(WPP_PAGE_SIZE * pageIndex).Take(WPP_PAGE_SIZE); My problem is that I get an error at query.Skip(...). Error 1 'System.Data.OrderedEnumerableRowCollection' does not contain a definition for 'Skip' and no extension method 'Skip' accepting a first argument of type 'System.Data.OrderedEnumerableRowCollection' could be found (are you missing a using directive or an assembly reference?) References I have: Microsoft.SharePoint System System.Core System.Data System.Data.DataSetExtensions System.Web System.Xml What am I missing?

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  • Clone LINQ To SQL object Extension Method throws object dispose exception....

    - by gtas
    Hello all, I have this extension method for cloning my LINQ To SQL objects: public static T CloneObjectGraph<T>(this T obj) where T : class { var serializer = new DataContractSerializer(typeof(T), null, int.MaxValue, false, true, null); using (var ms = new System.IO.MemoryStream()) { serializer.WriteObject(ms, obj); ms.Position = 0; return (T)serializer.ReadObject(ms); } } But while i carry objects with not all references loaded, while qyuerying with DataLoadOptions, sometimes it throws the object disposed exception, but thing is I don't ask for references that is not loaded (null). e.g. I have Customer with many references and i just need to carry on memory the Address reference EntityRef< and i don't Load anything else. But while i clone the object this exception forces me to load all the EntitySet< references with the Customer object, which might be too much and slow down the application speed. Any suggestions?

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  • Possible to use Tables of same type in Linq to SQL?

    - by Schneider
    Lets say I've got an object model, where I have many collections of the same type. For example something like class StockMarketData { List<SummaryData> WeeklySummary; List<SummaryData> MonthlySummary; } class SummaryData { DateTime DateTime {get; set;} double Value {get; set;} } Those lists will map onto database tables. If you actually use L2S to generate a model from the database you will get something like: class StockMarketData { List<WeeklySummaryData> WeeklySummary; List<MonthlySummaryData> MonthlySummary; } Even though WeeklySummaryData and MonthlySummaryData have the same shape. Is it possible for Linq to SQL to create tables from a database of summary data, but get each table to contain the same type (such as shown in the top example).

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  • Can anyone tell me if this is possible to do in Linq?

    - by user275561
    So I have been working and trying for a couple of hours. I am creating a BubbleBreaker type of game. I Can do it using for loop or while but I am trying to also get practice in using Linq. Here is what I am trying to do in pesudo code. Each Bubble has a Column and Row Property. If The bubble subtracts one from its Column property and finds the same Color bubble, it should Select it then Subtract -1 and see if two bubbles away there is also a same color bubble. If there is then subtract -2 and so on. So What I am trying to do is var test= _theBubbles.TakeWhile((i, s) => i.BubbleColor== bubble.BubbleColor)//Then somehow tell it to do bubble.Column-s and then Subtract s from bubble.Column So the Idea is to keep looking down the column till the bubble isnt the same

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  • How to pull a RANDOM and UNIQUE record from SQL via LINQ.

    - by Jeremy H
    Okay, I found lots of posts on SO about how to pull a RANDOM item from the database when using LINQ. There seems to be a couple of differnet ways to handle this. What I need to do though is pull a RANDOM item from the database that the user has not seen before. The data I am pulling from the database is very small. Is there any way I can just hit the database once for 1000 records and then randomly scroll through those? Should I put a cookie on the users system recording the IDs of which items they have seen, pull a random record, check to see if it is seen and if so, pull from the database again? That seems like performance issues just waiting to happen. I don't expect anyone to code it for me, I am just looking for concepts and pointing in the right direction of how I should go about this. Need more details? Just let me know!

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  • How can I transform a DataTable in a group-by date DataTable with LINQ?

    - by alex
    I have a untyped DataTable that looks like this (srcTbl): date col_1 col_2 ... col_n 1.3.2010 00:00 12.5 0 ... 100 1.3.2010 01:00 0 0 ... 100 1.3.2010 22:00 0 0 ... 100 1.3.2010 23:00 12.5 0 ... 100 ... 31.3.2010 00:00 2 0 ... 100 31.3.2010 01:00 2 0 ... 200 I need to sum up the rows grouped by dates to get a DataTable like that (dstTbl): date, col_1 col_2 ... col_n 1.3.2010 15 0 ... 400 ... 31.3.2010 4 0 ... 300 Is this possible by using LINQ and if then how?

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  • How to do Linq aggregates when there might be an empty set?

    - by Shaul
    I have a Linq collection of Things, where Thing has an Amount (decimal) property. I'm trying to do an aggregate on this for a certain subset of Things: var total = myThings.Sum(t => t.Amount); and that works nicely. But then I added a condition that left me with no Things in the result: var total = myThings.Where(t => t.OtherProperty == 123).Sum(t => t.Amount); And instead of getting total = 0 or null, I get an error: System.InvalidOperationException: The null value cannot be assigned to a member with type System.Decimal which is a non-nullable value type. That is really nasty, because I didn't expect that behavior. I would have expected total to be zero, maybe null - but certainly not to throw an exception! What am I doing wrong? What's the workaround/fix?

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  • What are the best blogs for staying up to date on C#, ASP.NET, LINQ, SQL, C++, Ruby, Java, Python?

    - by Arj
    Apologies if this repeats another - but I couldn't fine one like it. My day to day programming spans a fair number of technologies: C#, ASP.NET, LINQ / SQL, C++, Ruby, Java, Python in approximately that order. It's a struggle to keep up to date on any of best practices, new ideas, innovation and improvements, let alone all. Therefore, what would your top 1 blog be in each of these technologies and which technology do you find easiest to stay up to date with? I'd have a bias towards blogs with broad and high level rather than narrow and detailed content / solutions / examples.

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  • ASP.NET MVC / Linq-to-SQL classes: Can I get it to infer readable display names?

    - by Gary McGill
    If I have a table Orders with fields CustomerID, OrderID and OrderDate, then the "Linq-to-SQL classes" generated class will be called Orders, with members called CustomerID, OrderID and OrderDate. So far so good. However, if I then do Html.LabelFor(m => m.OrderDate) then the generated text will be "OrderDate" instead of "Order Date". I tried using Order_Date as the field name, but that didn't work. Is there any way to get it to infer a better display name? [I know that I can use data annotations to specify the display name explicitly, but I really don't want to do that for all my classes/members - I just want it to work by convention.]

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  • What is the max LINQ Expression Trees can do?

    - by yeeen
    What is the maximun that LINQ expression Tree can do? Can it define a class? How about a method, with all the declared name, modifiers, parametertype and return type? Must the program always define the tree himself? Is it possible to generate the tree from a given C# file? Where can I get resources to learn about writing basic to advanced Expression Tree and Expression Tree Visitor? (articles and videos will be great) Thanks for those who are able to help...

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  • Another Permutation Word Conundrum... With Linq?

    - by CraigF
    I have seen many examples of getting all permutations of a given set of letters. Recursion seems to work well to get all possible combinations of a set of letters (though it doesn't seem to take into account if 2 of the letters are the same). What I would like to figure out is, could you use linq (or not) to get all possible combinations of letters down to 3 letter combinations. For example, given the letters: P I G G Y I want an array of all possible cominations of these letters so I can check against a word list (scrabble?) and eventually get a list of all possible words that you can make using those letters (from 3 letters up to the total, in this case 5 letters).

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  • Can I use Linq to project a new typed datarow?

    - by itchi
    I currently have a csv file that I'm parsing with an example from here: http://alexreg.wordpress.com/2009/05/03/strongly-typed-csv-reader-in-c/ I then want to loop the records and insert them using a typed dataset xsd to an Oracle database. It's not that difficult, something like: foreach (var csvItem in csvfile) { DataSet.MYTABLEDataTable DT = new DataSet.MYTABLEDataTable(); DataSet.MYTABLERow row = DT.NewMYTABLERow(); row.FIELD1 = csvItem.FIELD1; row.FIELD2 = csvItem.FIELD2; } I was wondering how I would do something with LINQ projection: var test = from csvItem in csvfile select new MYTABLERow { FIELD1 = csvItem.FIELD1, FIELD2 = csvItem.FIELD2 } But I don't think I can create datarows like this without the use of a rowbuilder, or maybe a better constructor for the datarow?

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  • why LINQ 2 SQL sometime add a field like select 1 as test, others valid fields....

    - by Fredou
    I have to concat 2 linq2sql query and I have an issue since the 2 query doesn't return the same number of columns, what is weird is after a .ToList() on the queries, they can concat without problem. The reason is, for some linq2sql reason, I have 2 more column named test and test2 which come from 2 left outer join that linq2sql automatically create, something like "select 1 as test, tablefields" Is there any good reason for that? how to remove this extra "1 as test" field? here a few of examples of what it look like: google result for linq 2 sql "select 1 as test"

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  • Tag filtering Query using T-SQL and Linq-to-SQL?

    - by EdenMachine
    I'm trying to figure out how to allow a user to enter in a string of tags (keywords separated by spaces) in a textbox to filter a grid of results. Here are the tables: PACKETS *PacketID Name PACKETTAGS *PacketTagID PacketID TagID Tags *TagID Name Here is the basic query without the WHERE parameters: SELECT Packets.Name, Tags.Name AS Tag, PacketTags.PacketTagID FROM Packets INNER JOIN PacketTags ON Packets.PacketID = PacketTags.PacketID INNER JOIN Tags ON PacketTags.TagID = Tags.TagID I need to filter out all the Packets that don't have tags that match any of the words BUT ALSO ONLY include the Packets that have the tags entered in the string of text (spaces separate the tags when entered into the textbox) I'm starting with the basics by figuring this out in t-SQL first but ultimately I need to be able to do this in Linq-to-SQL

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  • How to OrderBy on a generic IEnumerable (IEnumerable<T>) using LINQ in C#?

    - by Jeffrey
    In my generic repository I have below method: public virtual IEnumerable<T> GetAll<T>() where T : class { using (var ctx = new DataContext()) { ctx.ObjectTrackingEnabled = false; var table = ctx.GetTable<T>().ToList().AsReadOnly(); return table; } } T is a Linq to Sql class and I want to be able to OrderBy on a particular property. Say if T has property name "SortOrder" then do OrderBy on this property. But I am not sure how I can achieve this. So I need some helps. Thank you!

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  • How to update a table in database using LINQ in F#?

    - by sudaly
    I have seen plenty of examples on how to query the database but nothing on how to update records. Below is the simple code that I wrote to retrieve a table, but can someone explain me how can I modify a field, say lastActiveDate, and update the table on the database Thank you, suday open System open Microsoft.FSharp.Linq let connString = "Server=localhost;Database=myDb;Trusted_Connection=True;" let db = new MyDb(connString) db.Log <- System.Console.Out let res = Query.query <@ seq { for users in db.userAccounts do yield users } @> |> List.ofSeq printfn "Totla users: %d" res.Length

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  • building an ASP NET MVC site, should i go with linq to sql?

    - by aspm
    so i'm about to start a new website from scratch and i've spent about a week trying to figure out what technology to go with. i'm sold on ASP NET MVC. i'm 100% sure i'm going to love using that. but what i am not so sure about yet is using LINQ 2 SQL. so far i've gathered some data... 1) stack overflow uses it - can't be that bad 2) can be REALLY slow if you don't take advantage of compiled queries 3) will always be slower than ADO net, but can be almost just as fast if using #2 in the proper places 4) is NOT the preferred MS solution (there was a thread here on SO about dropping support) i'm itching to use it, but just want to make sure it's the best for me. i come from a heavy ADO/stored procedure and traditional asp net background (this will be my first experience with ASP MVC).

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  • Upgrade to 4.0 Framework, then downgraded, now can't find Linq namespace?

    - by CubanX
    I just upgraded from VS2008 to VS2010. In the process, I allowed it to upgrade my DLL's to 4.0. I've decided that wasn't a good idea and now I've rolled back. It all works fine in VS2010, but when it hits my CI server (CruiseControl.Net), I get an error of: The type or namespace name 'Linq' does not exist in the namespace 'System' (are you missing an assembly reference? 3.5 is on the server, and other projects that use 3.5 build fine, so I don't think it's a framework issue. Anyone have any hints?

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  • LINQ query for tag system: Matching any of several tags?

    - by David Veeneman
    I am just getting started with LINQ. I am creating an Entity Framework app that uses the canonical Post and Tag model. A Post contains an ID, Text, and Tags, and a Tag contains an ID, a Name, and Posts. A previous thread on StackOverflow showed me how to query for a Post that matches all Tag objects (A and B and C) in a search list. But how would I query for a Post that matches any Tag (A or B or C) in the list? Thanks for your help.

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  • Why did the following linq to sql query generate a subquery?

    - by Xaisoft
    I did the following query: var list = from book in books where book.price > 50 select book; list = list.Take(50); I would expect the above to generate something like: SELECT top 50 id, title, price, author FROM Books WHERE price > 50 but it generates: SELECT [Limit1].[C1] as [C1] [Limit1].[id] as [Id], [Limit1].[title] as [title], [Limit1].[price] as [price], [Limit1].[author] FROM (SELECT TOP (50) [Extent1].[id] as as [Id], [Extent1].[title] as [title], [Extent1].[price] as [price], [Extent1].[author] as [author] FROM Books as [Extent1] WHERE [Extent1].[price] > 50 ) AS [Limit1] Why does the above linq query generate a subquery and where does the C1 come from?

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  • How to format complex chained Linq statements for readibility?

    - by Joan Venge
    I have some code like this: var effects = xElement.Elements ( "Effects" ).Elements ( "Effect" ).Select ( e => new Effect ( ( EffectType ) Enum.Parse ( typeof ( EffectType ), ( string ) e.Elements ( "Type" ).FirstOrDefault ( ) ), e.Elements ( "Options" ).Any ( ) ? e.Elements ( "Options" ).Select ( o => ( object ) o.Elements ( "Option" ).Select ( n => n.Value ).First ( ) ) : null ) ) .ToList ( ); But currently this doesn't look as readable and I am not sure where I should add a new line and/or indent for readability. Any suggestions I could use to make consistent, readable linq blocks?

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  • Linq GroupBy - how to specify the grouping key at runtime?

    - by toasteroven
    is there a good way to do a Linq GroupBy where the grouping key is determined at runtime? e.g. I want the grouping key to be built from a user-selected list of fields - can you do this? I know I can do it easily if I convert everything to a table of strings, but I was wondering if there was an elegant or clever way to accomplish this otherwise. class Item { public int A, B; public DateTime D; public double X, Y, Z; } I have a List<Item> called data. I want to do things like retrieve the sum of X grouped by A, or the sums of X, Y, and Z, grouped by A and B. but what fields go into the grouping should be able to be specified at runtime in some way.

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  • Please help me convert this C# 2.0 snippet to Linq.

    - by Hamish Grubijan
    This is not a homework ;) I need to both A) optimize the following code (between a TODO and a ~TODO) and B) convert it to [P]Linq. Better readability is desired. It might make sense to provide answers to A) and B) separately. Thanks! lock (Status.LockObj) { // TODO: find a better way to merge these dictionaries foreach (KeyValuePair<Guid, Message> sInstance in newSInstanceDictionary) { this.sInstanceDictionary.Add(sInstance.Key, sInstance.Value); } foreach (KeyValuePair<Guid, Message> sOperation in newSOperationDictionary) { this.sOperationDictionary.Add(sOperation.Key, sOperation.Value); } // ~TODO }

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  • Is there a way to make this C# method shorter and more readable with the help of Linq?

    - by Hamish Grubijan
    The following works, but I figured - since it is all based on IEnumerable, Linq can come handy here is well. By the way, is there an equivalent to Directory.GetFiles() which would return an IEnumerable instead of the array? If it exists, then would it make the code run any faster? The last part of the question is inspired by Python language which favors lightweight generators over concrete lists. private IEnumerable<string> getFiles(string strDirectory, bool bCompressedOnly) { foreach (var strFile in Directory.GetFiles(strDirectory)) { // Don't add any existing Zip files since we don't want to delete previously compressed files. if (!bCompressedOnly || Path.GetExtension(strFile).ToLower().Equals(".zip")) { yield return strFile; } } foreach (var strDir in Directory.GetDirectories(strDirectory)) { foreach (var strFile in getFiles(strDir, bCompressedOnly)) { yield return strFile; } } }

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