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  • How do I programmatically translate a LINQ query to readable English text that correctly describes t

    - by eniac
    I am working on a project that uses Albahari's PredicateBuilder library http://www.albahari.com/nutshell/ to create a linq expression dynamically at run time. I would like to find a way to translate this dynamically created linq predicate of type Expression<Func<T, bool>> into a readable english statement at runtime. I'll give a statically created linq statement as an example: from p in Purchases select p where p.Price 100 && p.Description != "Bike". For this linq statement I would want to dynamically generate at runtime an english description along the lines of: "You are searching for purchases where the price is greater than 100 and the description is not bike". Are there any libraries that already exist which accomplish this goal, keep in mind I am using PredicateBuilder to dynamically generate the where predicate. If no solution exists how would you go about building a solution? Thanks!

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  • LINQ causing my obfuscator to break

    - by JL
    I have the following LINQ that is causing my obfuscator to break. .Where(f => f.FileName == fileName).OrderByDescending(f => f.Position).FirstOrDefault(); Is there another way I could reword this LINQ statement to test against my obfuscator? I've reported the bug, but it could take 1-2 months to fix, so I need to try recode this LINQ in the meantime.

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  • Create LINQ to entities OrderBy expression on the fly

    - by AyKarsi
    I'm trying to add the orderby expression on the fly. But when the query below is executed I get the following exception: System.NotSupportedException: Unable to create a constant value of type 'Closure type'. Only primitive types ('such as Int32, String, and Guid') are supported in this context. The strange thing is, I am query exactly those primitive types only. string sortBy = HttpContext.Current.Request.QueryString["sidx"]; ParameterExpression prm = Expression.Parameter(typeof(buskerPosting), "posting"); Expression orderByProperty = Expression.Property(prm, sortBy); // get the paged records IQueryable<PostingListItemDto> query = (from posting in be.buskerPosting where posting.buskerAccount.cmsMember.nodeId == m.Id orderby orderByProperty //orderby posting.Created select new PostingListItemDto { Set = posting }).Skip<PostingListItemDto>((page - 1) * pageSize).Take<PostingListItemDto>(pageSize); Hope somebody can shed some light on this!

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  • Linq ChangeConflictException occurs when submitting DataContext changes

    - by Alex
    System.Data.Linq.ChangeConflictException: 2 of X updates failed. at System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode) at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode) at PROJECT.Controllers.HomeController.ClickProc(Int32 id, String code, String n) This is what I get very often. This action is done thousands of times a day, and I get this exception about once every 5 seconds. From what I understand it happens when something changes in the database in the period between creating DataContext and updating it. Am I right? How can I fix it? Update I just debugged the error and found the following: Table name: dbo.Stats current value: 9852039 original value: 9852038 database value: 9852039 The Stats table is updated constantly. So how can I still make LINQ save the changes. With "classical" SQL Server access through SqlDataCommand I never had problems like that.

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  • How to deal with the limited Linq Support of OData (Open Data Protocol)

    - by user341127
    I have a software, which uses a lot of Linq to SQL. Recently, I want to immigrate to OData (or WCF Data Service) architecture. But I met too many problems in Linq for the Linq support of OData is so limited. I have to modify most of my Linq statements and test them thoroughly again. I am wondering whether there is a system way to solve such a problem instead of my manual work. For example, by an external package. BTW, now I have no confidence to use OData as a kind of architecture. You are appreciated to share your ideas. Thank you in advance, Ying

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  • The question about the basics of LINQ to SQL working

    - by Alex
    I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer Get all customers from the database ("SELECT * FROM Customers"), move them to the Customers array and then make a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

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  • time calculation within LINQ

    - by d daly
    Hi I want a linq query to return a calculated timespan, i have used the timespan function before, but im not sure how to incorporate it into linq. Basically the linq is returning a datetime field which i want to subtract from the current datetime to get days and hours. Any help appreciated! Thanks

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  • C# + Querying XML with LINQ

    - by user336786
    Hello, I'm learning to use LINQ. I have seen some videos online that have really impressed me. In an effort to learn LINQ myself, I decided to try to write a query to the NOAA web service. If you put "http://www.weather.gov/forecasts/xml/sample_products/browser_interface/ndfdBrowserClientByDay.php?zipCodeList=20001&format=24+hourly&startDate=2010-06-10&numDays=5" in your browser's address bar, you will see some XML. I have successfully retrieved that XML in a C# program. I am loading the XML into a LINQable entity by doing the following: string xml = QueryWeatherService(); XDocument weather = XDocument.Parse(xml); I have a class called DailyForecast defined as follows: public class DailyForecast { public float HighTemperature { get; set; } public float LowTemperature { get; set; } public float PrecipitationPossibility { get; set; } public string WeatherSummary { get; set; } } I'm trying write a LINQ query that adheres to the structure of my DailyForecast class. At this time, I've only gotten to this far: var results = from day in response.Descendants("parameters") select day; Not very far I know. Because of the structure of the XML returned, I'm not sure it is possible to solely use a LINQ query. I think the only way to do this is via a loop and traverse the XML. I'm seeking someone to correct me if I'm wrong. Can someone please tell me if I can get results using purely LINQ that adhere to the structure of the DailyForecast class? If so, how? Thank you!

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  • LINQ version of SQL's LIKE statement

    - by Erwin
    Hi fellow coders I'm new at LINQ, searching the net for LINQ samples that mimic SQL's LIKE statement doesn't satisfy myself. What I want is producing the same query result as this SQL SELECT * FROM table_1 WHERE column_1 LIKE '__0%' I want to query from table_1 where column_1's third character is '0' Is there equivalent statement in LINQ :D thank you

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  • Open source LINQ search engine for website

    - by Noel
    I want to add a search engine to my website. I want it to handler boolean searches and give me a list of results in order or best match. I need it to be able to work with LINQ, because I want to add additional where clauses to the final query that gets run. I am looking for the best open source .NET search engine that works with LINQ. I like lucene.net but the problem is the LINQ interface (LINQ to Lucene) hasn't been updated since 2008. Are there any good options out there?

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  • PHP simplexml Entities

    - by FFish
    What's going one here? $string = <<<XML <?xml version="1.0" encoding="UTF-8"?> <album> <img src="002.jpg" caption="w&aacute;ssup?" /> </album> XML; $xml = simplexml_load_string($string); // $xmlobj = simplexml_load_file("xml.xml"); // same thing echo "<pre>"; var_dump($xml); echo "</pre>"; Error: Warning: simplexml_load_string() [function.simplexml-load-string]: Entity: line 5: parser error : Entity 'aacute' not defined

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  • Entity framework with Linq to Entities performance

    - by mare
    If I have a static method like this public static string GetTicClassificationTitle(string classI, string classII, string classIII) { using (TicDatabaseEntities ticdb = new TicDatabaseEntities()) { var result = from classes in ticdb.Classifications where classes.ClassI == classI where classes.ClassII == classII where classes.ClassIII == classIII select classes.Description; return result.FirstOrDefault(); } } and use this method in various places in foreach loops or just plain calling it numerous times, does it create and open new connection every time? If so, how can I tackle this? Should I cache the results somewhere, like in this case, I would cache the entire Classifications table in Memory Cache? And then do queries vs this cached object? Or should I make TicDatabaseEntities variable static and initialize it at class level? Should my class be static if it contains only static methods? Because right now it is not.. Also I've noticed that if I return result.First() instead of FirstOrDefault() and the query does not find a match, it will issue an exception (with FirstOrDefault() there is no exception, it returns null). Thank you for clarification.

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  • Count number of given object in a list with LINQ

    - by Aaginor
    I have a list which can contain multiple occurrences of the same object. Now I need to count, how often the given object is contained in this list. int count = 0; foreach (IMyObject item in myList) if (item == object2Count) count++; I am sure that this can be done nicer with LINQ, but LINQ is still a mystery to me. My first question is: How would I count the objects via LINQ and the second question: Will this LINQ version be slower or faster? I am using a ObservableCollection and the number of items in the list is usally rather small ... usally not more then 20. Thanks in advance, Frank

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  • Using Linq to SQL change events with attribute-based mapping

    - by R Mene
    I'm writing a new ASP.NET MVC2 application using Linq to SQL. This application depends on an existing SQL database. I am using attribute-based mapping to map my database fields to my Linq to SQL entities. I also need to make use of Linq to SQL's On[Property]Changed methods so I can perform change-auditing of database tables within my application. Whereas the documentation explains how to do this when using Linq to SQL's ORM and dbml files (i.e. by writing partial classes), it is not clear how to do with when using attribute-based mapping or when using XML-based mapping. It would be very helpful if someone could describe how to do this.

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  • Converting html entities into their values in python

    - by tipu
    I use this regex on some input, [^a-zA-Z0-9@#] However this ends up removing lots of html special characters within the input, such as 227;, #1606;, #1588; (i had to remove the & prefix so that it wouldn't show up as the actual value..) is there a way that I can convert them to their values so that it will satisfy the regexp expression? I also have no idea why the text decided to be so big.

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  • How to user IN operator in Linq?

    - by Umapathy
    Query: Select * from pu_Products where Part_Number in ('031832','027861', '028020', '033378') and User_Id = 50 and Is_Deleted = 0 The above mentioned query is in SQL and i need the query might be converted into Linq. Is there any option using the "IN" operator in Linq?. can you convert above mentioned query into Linq?

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  • 'Random' Orderby in webservice using LINQ To Entities

    - by MrDean
    Morning all Now I know there is a reason to this odering but my tiny little brain can't get my head around it. I am using a webservice to pull through data to a webp[age and have the following that is so far pulling data through from UUF1: public string[] GetBuyer(string Memberkey) { try { WebService.EntitiesConnection buyer = new WebService.EntitiesConnection(); return buyer.tblProducts .Where(p => p.MemberId == Memberkey) .OrderBy(p => p.UnitUserfield1) .Select(p => p.UnitUserfield1) .Distinct() .ToArray(); } catch (Exception) { return null; } } This works fine and pulls the data through but in a strange order. Where I would expect results of A B C D E F, it appears to be returning A C E B D F. Could someone point out the error in my ways please?

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  • Translate an IQueryable instance to LINQ syntax in a string

    - by James Dunne
    I would like to find out if anyone has existing work surrounding formatting an IQueryable instance back into a LINQ C# syntax inside a string. It'd be a nice-to-have feature for an internal LINQ-to-SQL auditing framework I'm building. Once my framework gets the IQueryable instance from a data repository method, I'd like to output something like: This LINQ query: from ce in db.EiClassEnrollment join c in db.EiCourse on ce.CourseID equals c.CourseID join cl in db.EiClass on ce.ClassID equals cl.ClassID join t in db.EiTerm on ce.TermID equals t.TermID join st in db.EiStaff on cl.Instructor equals st.StaffID where (ce.StudentID == studentID) && (ce.TermID == termID) && (cl.Campus == campusID) select new { ce, cl, t, c, st }; Generates the following LINQ-to-SQL query: DECLARE @p0 int; DECLARE @p1 int; DECLARE @p2 int; SET @p0 = 777; SET @p1 = 778; SET @p2 = 779; SELECT [t0].[ClassEnrollmentID], ..., [t4].[Name] FROM [dbo].[ei_ClassEnrollment] AS [t0] INNER JOIN [dbo].[ei_Course] AS [t1] ON [t0].[CourseID] = [t1].[CourseID] INNER JOIN [dbo].[ei_Class] AS [t2] ON [t0].[ClassID] = [t2].[ClassID] INNER JOIN [dbo].[ei_Term] AS [t3] ON [t0].[TermID] = [t3].[TermID] INNER JOIN [dbo].[ei_Staff] AS [t4] ON [t2].[Instructor] = [t4].[StaffID] WHERE ([t0].[StudentID] = @p0) AND ([t0].[TermID] = @p1) AND ([t2].[Campus] = @p2) I already have the SQL output working as you can see. I just need to find a way to get the IQueryable to translate into a string representing its original LINQ syntax (with an acceptable translation loss). I'm not afraid of writing it myself, but I'd like to see if anyone else has done this first.

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  • Linq To Entities

    - by JkenshinN
    This has probably been answer already but I am trying to return the primary key after inserting a record to the database. Does anyone know how this is accomplish after the record has been created?

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