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  • Is it possible to create custom methods in entity classes in linq to sql

    - by doekman
    I have a table Site in SQL with (amongst others) three properties idReviewer1, idReviewer2, idReviewer3. Now I would like to create a methods on the entity class of Site to check if a user is a reviewer: partial class Site { public bool IsReviewer(int idUser) { return idReviewer1 == idUser || idReviewer2 == idUser || idReviewer3 == idUser; } } and I use it like this: return from s in db.Sites where s.IsReviewer(user) select s; However, Linq to SQL doesn't know how to translate this to SQL. I get the following error message: Method 'Boolean IsReviewer(Int32)' has no supported translation to SQL. I'd rather not write this: return from s in db.Sites where idReviewer1 == idUser || idReviewer2 == idUser || idReviewer3 == idUser select s; Is there any way to put this functionality in one place, without resorting to SQL?

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  • DataTable linq query iteration

    - by Ravi
    Hi, I want to Enumerate Linq Query. Below i specified example. EX: DataTable _slidingDataTable = new DataTable("test"); for(int i=0; i<5;i++) { DataRow row = _slidingDataTable.NewRow(); startPosition = DateTime.Now; for(int i=0; i<5;i++) { _slidingDataTable.Columns.Add("TransferTime"); row[columnName] = startPosition ; _slidingDataTable.Columns.Add("TransferData"); row[columnName] = "Test"+i; } _slidingDataTable.Rows.Add(row); } var query1 = from myRow in _slidingDataTable.AsEnumerable() where myRow.Field<DateTime>("TransferTime") == startPosition select myRow; This query output should be collection of rows. How to get collection row & iterate.

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  • linq and contains

    - by kusanagi
    i have func public PageOfList<ConsaltQuestion> Filter(int? type, int pageId, EntityCollection<ConsaltCost> ConsaltRoles) { // return _dataContext.ConsaltQuestion.Where((o => o.Type == type || type == null) && (o=>o.Paid == paid)); return (from i in _dataContext.ConsaltQuestion where ((i.Type == type || type == null) && (i.Paid == true) && (ConsaltRoles.Contains(ConsaltCostDetails(i.Type.Value)))) select i).ToList().ToPageOfList(pageId, 20); } it return error LINQ to Entities does not recognize the method 'Boolean Contains(mrhome.Models.ConsaltCost)' method, and this method cannot be translated into a store expression. how can i fix it?

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  • Compare two object lists with LINQ on specific property

    - by Niklas
    I have these two lists (where the Value in a SelectListItem is a bookingid): List<SelectListItem> selectedbookings; List<Booking> availableBookings; I need to find the ids from selectedBookings that are not in availableBookings. The LINQ join below will only get me the bookingids that are in availableBookings, and I'm not sure how to do it the other way around. != won't work since I'm comparing strings. results = ( from s in selectedbookings join a in availableBookings on s.bookingID.ToString() equals a.Value select s);

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  • Using a linq or lambda expression in C# return a collection plus a single value

    - by ahsteele
    I'd like to return a collection plus a single value. Presently I am using a field to create a new list adding a value to the list and then returning the result. Is there a way to do this with a linq or lambda expression? private List<ChargeDetail> _chargeBreakdown = new List<ChargeDetail>(); public ChargeDetail PrimaryChargeDetail { get; set; } public List<ChargeDetail> ChargeBreakdown { get { List<ChargeDetail> result = new List<ChargeDetail>(_chargeBreakdown); result.Add(PrimaryChargeDetail); return result; } }

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  • [LINQ noob] Please help me convert this Python 3.x snippet to .net LINQ.

    - by Hamish Grubijan
    I want to sort elements of a HashSet<string> and join them by a ; character. Python interpreter version: >>> st = {'jhg', 'uywer', 'nbcm', 'utr'} >>> strng = ';'.join(sorted(s)) >>> strng 'ASD;anmbh;ashgg;jhghjg' C# signature of a method I seek: private string getVersionsSorted(HashSet<string> versions); I can do this without using Linq, but I really want to learn it better. Many thanks!

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  • Creating LINQ to SQL for counting a parameter

    - by Matt
    I'm trying to translate a sql query into LINQ to SQL. I keep getting an error "sequence operators not supported for type 'system.string'" If I take out the distinct count part, it works. Is it not because I'm using the GROUP BY? SELECT COUNT(EpaValue) AS [Leak Count], Location, EpaValue AS [Leak Desc.] FROM ChartMes.dbo.RecourceActualEPA_Report WHERE (EpaName = N'LEAK1') AND (Timestamp) '20100429030000' GROUP BY EpaValue, Location ORDER BY Location, [Leak Count] DESC Dim temp = (From p In db2.RecourceActualEPA_Reports _ Where (p.Timestamp = str1stShiftStart) And (p.Timestamp < str2ndShiftCutoff) _ And (p.EpaName = "Leak1") _ Select p.EpaName.Distinct.Count(), p.Location, p.EpaValue)

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  • LINQ saving images to varbinary

    - by m4rc
    I'm having issues saving images to a varbinary(Max) field using LINQ. I can save files in the region of 10KB to the database no problems, but when it comes to files bigger than that, it's as though it doesn't even try. I've had a look in the SQL Server Profiler and when the file is around 10KB I can see the full insert statement in the detail pane. However, when the file is a bit bigger, the detail pane doesn't show anything, although any data besides the varbinary field is written to the database. The data is in the Data Object just before SubmitChanges so I can't figure out what's happening between now and then!

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  • Linq: comparison with nonexisting value should not cause the exception, but it does

    - by Seacat
    Hello, Given I don't know if the parameter will be null or not and I want to use it in the following way: if Param != null then compare with its id if Param == null then compare with null. Something like that: var c = from cat in context.Categories where ParamCat != null && cat.ParentId == ParamCat.Id || ParamCat == null && cat.ParentId == null select c; If ParamCat is null as soon as I try to get something from c (for example c.Count()) it throws the exception. Usually when we use some kind of condition it stop comparison as soon as condition fail especially if we use AND. For example this code will not cause any exception: if (ParamCat != null && cat.ParentId == RaramCat.Id) { } If so, why the linq code above throw exception? (Null reference) Thanks

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  • Using multiple databases within one application (ASP.NET MVC, LINQ to SQL)

    - by Alex
    I have a web application made for several groups of people not connected with each other. Instead of using one database for all of them, I'm thinking about making separate databases. This will improve the speed of the queries and make me free from checking to what group the user belongs. But since I'm working with LINQ to SQL, my classes are explicitly connected with the databases, so I will have to make separate DataContexts for all of the databases. So how can I solve this problem? Or should I just not bother and use one database only?

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  • Safely dereferencing FirstOrDefault call in Linq c#

    - by samy
    For brevity's sake in my code, i'd like to be able to do the following: having a collection, find the first element matching a lambda expression; if it exists, return the value of a property or function. If it doesn't exist, return null. var stuff = {"I", "am", "many", "strings", "obviously"}; var UpperValueOfAString = stuff.FirstOrDefault(s => s.contains("bvi")).ToUpper(); // would return "OBVIOUSLY" var UpperValueOfAStringWannabe = stuff.FirstOrDefault(s => s.contains("unknown token")).ToUpper(); // would return null Is it possible with some linq-syntax-fu or do i have to check explicitly for the return value before proceeding?

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  • LINQ - Using where or join - Performance difference ?

    - by Patrick Säuerl
    Hi Based on this question: http://stackoverflow.com/questions/3013034/what-is-difference-between-where-and-join-in-linq My question is following: Is there a performance difference in the following two statements: from order in myDB.OrdersSet from person in myDB.PersonSet from product in myDB.ProductSet where order.Persons_Id==person.Id && order.Products_Id==product.Id select new { order.Id, person.Name, person.SurName, product.Model,UrunAdi=product.Name }; and from order in myDB.OrdersSet join person in myDB.PersonSet on order.Persons_Id equals person.Id join product in myDB.ProductSet on order.Products_Id equals product.Id select new { order.Id, person.Name, person.SurName, product.Model,UrunAdi=product.Name }; I would always use the second one just because it´s more clear. My question is now, is the first one slower than the second one? Does it build a cartesic product and filters it afterwards with the where clauses ? Thank you.

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  • Linq-to-SQL- A stored procedure returns field which is not there in Mapped Table Info

    - by jalpesh
    We are using Linq-to-SQL with stored Procedures we need help on one of our problem. We are having user tables which is having all field required for user table like firstname,lastname and other fields that table is also there in our DBML files.Now the problem is that we are having a stored procedure that is mapped to table-User returning a field called fullname (Combination of firstname and lastname)which is not there in usertable. So what is the best way to slove this. Another thing is that one of other stored procedure return inner join of two tables with mix columns in this case how can i mapped that stored procedure with Table mapped info class in our dbml files.

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  • Linq to SQL inheritance and Table per Class - approach needed for multiple roles

    - by Ash Machine
    I am using L2S and an inheritance model for mapping Persons against certain roles. Guy Burstein's excellent blog post explains how to accomplish this: http://blogs.microsoft.co.il/blogs/bursteg/archive/2007/10/01/linq-to-sql-inheritance.aspx However, I have a specific case where a Person has multiple roles. For example 'Jane Doe' is a Contact and a Programmer. In this model, she would need two rows in the People table, one as Contact (PersonType = 1) and one as Programmer (PersonType = 3). If she changes her last name, and that update happens in her role as Contact, I would need to change all instances of 'Jane Doe' to reflect the name change everywhere. What sort of best approach (improved data structure) could be used to change last name within all roles? Finally, I am hoping to avoid overriding each general form update events to include all instances, but that may be the only way. Any suggestions or approaches appreciated.

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  • Select a Column Dynamically using LINQ?

    - by vsj
    Hi all I am trying to do a very simple dynamic query which will select a column dynamically I mean the selection of column would depend upon another query so I would select x col if cond1 and y if cond2 so I tried using query.Select(colname) using the extension method also tried using Func< but I am not sure how to go about this I have read about dynamic extension for linq and also reflection but woth reflection to the GetValue function does not return value for my column in database. please help me out I am jus trying to select a column dynamically at runtime and no condtions really on it.

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  • Using database default values with Linq to SQL codewise

    - by Ivo
    I am using Dynamic Data with linq to SQL and SQL Server 2008. I have a GUID column that gets his value from the default value with newguid(). When I set IsDbGenerated to true in the designer it works like a charm. But when I renew table this property is set back to false again. So I added it to the metadata. For some reason it's not being pickup, "00000000-0000-0000-0000-000000000000" is being inserted in database. The displayname and readonly change are being pick up. What am I missing? [MetadataType(typeof(CMS_Data_HistoryMetadata))] public partial class CMS_Data_History { } [TableName("Content")] public class CMS_Data_HistoryMetadata { [DisplayName("Pagina Title")] public object pageTitleBar { get; set; } [ReadOnly(true)] [DisplayName("Versie")] public object version_date { get; set; } [ColumnAttribute(IsDbGenerated = true)] public object entity_id; }

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  • beginner Linq syntax and EF4 question

    - by user564577
    Question With the following linq code snip I get a list of clients with address filtered by the specifications but the form of the entities returned is not what i had expected. The data is 1 client with 2 addresses and 1 client with 1 address. The query returns 3 rows of clients each with 1 address Client 1 = Address1 Client 1 = Address2 Client 2 = Address3 var query = from t1 in context.Clients.Where(specification.SatisfiedBy()).Include("ClientAddresses") join t2 in context.ClientAddresses.Where(spec.SatisfiedBy()) on t1.ClientKey equals t2.ClientKey select t1; My expectation was a little more like a list with only two clients in it, one client with a collection of two addresses and one client with a collection of one address. Client 1 = Address1 / Address2 Client 2 = Address3 What am I missing??? Thanks!

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  • LINQ Multiple LIKE based on List

    - by Bathan
    I have a list of keywords in an ArrayList and I wanted to be able to build a query to find records in a table based on this keywords. Since the list of keywords is dynamic I cannot build a fixed query here. if I do something like this: foreach (string kw in keywords) { query = query.Where(p => p.Name.StartsWith(kw)); } The "StartsWith" is required here because I need to search those records that actually start with the provided keyword. In T-SQL it Would be something like this Select * from Table where Name like 'keyword1%' or Name like 'keyword2%' or Name like 'keyword3%' or ... But I need to be able to do this in LINQ...Is this possible?

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  • Linq to SQL and Realtime Data

    - by Jeremy
    I have an application that needs to constantly (every 50ms), call to an MVC action, and pickup/drop off data. I am using Linq to SQL and MVC because of how simple they are to implement, and I know that they aren't perfect when it comes to performance, but it works relatively well, but the best speed I can get with my current approach is 200ms (without requests overlapping). Each call to the site will create a new instance of the datacontext, query/insert it and return that data. Is there a way to have the datacontext static, but submitchanges say every 5 seconds, so that i am pretty much hitting an in-memory version of the data?

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  • Datatable -filter records with linq based on some internal index

    - by Karan
    Hello Guys, I have a datatable with plenty of records. And i have a range like lowerRange = 10 and upperRange = 200. I want the pull the records starting at row 10 till row 200. Now i don't want to add any new index based column into the datatable. Is there any way with the help of linq, i can pull the set of rows based on some internal datatable index? I guess, the datatable must be maintaining some row index implicitly. Please suggest.

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  • Convert Python 3.x snippet to C#/LINQ.

    - by Hamish Grubijan
    I want to sort elements of a HashSet<string> and join them by a ; character. Python interpreter version: >>> st = {'jhg', 'uywer', 'nbcm', 'utr'} >>> strng = ';'.join(sorted(s)) >>> strng 'ASD;anmbh;ashgg;jhghjg' C# signature of a method I seek: private string getVersionsSorted(HashSet<string> versions); I can do this without using Linq, but I really want to learn it better. Many thanks!

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  • linq .net with dynamically generated controls

    - by Stuart
    This is a very strange problem and i really dont have a clue whats causing it. What is supposed to happen is that a call to the BLL then DAL returns some data via a linq SPROC call. The retunred IMultipleResults object is processed and all results stored in a hashtable. The hashtable is stored in session and then the UI layer uses these results to dynamically generate some gridviews. Easy you would think. But if i run the code i dont get any gridviews. If i take out the call to the BLL and DAL the gridviews appear but with nothing in them? Why is it the page renders correctly when i take out the call to get the data? Thanks.

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  • Linq to SQL - design question.

    - by UshaP
    HI, Currently i have one big datacontex with 35 tables (i dragged all my DB tables to the designer). I must admit it is very comfortable cause i have ORM to my full DB and query with linq is easy and simple. My questions are: 1. Would you consider it bad design to have one datacontext with 35 tables or should i split it to logic units? 2. Is there any performance penalties for using such a big datacontext? Thanks, Pini.

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  • Getting differences between collections in LINQ

    - by dotnetdev
    Hi, I have a collection of image paths, and a larger collection of Image objects (Which contain a path property). I have the code to check for any matching images, but if there are supposed to be four matching image paths (as that is how many are in the first collection), and there is less than this, how can I get the missing one without writing loops? List<string> ImagesToCheck = new List<string>() { "", "s", "ssdd" }; IEnumerable<HtmlImage> Images = manager.ActiveBrowser.Find.AllControls<HtmlImage>(); var v = from i in Images where ImagesToCheck.Any(x => x == i.Src) select i; if (v.Count() < 3) { } So I need to get the items which are not in the collection titled v, but are in ImagesToCheck. How could I do this with LINQ? Thanks

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  • Performing multiple operations if condition is satisfied in ternary operator in linq

    - by user1575914
    I am a beginner in LINQ.I want to perform some conditional operation lik follows, (from emp in Employees let DOB=emp.BirthDate.GetValueOrDefault() let year=DOB.Year let month=DOB.Month let EmpAgeInYearsToday=DateTime.Now.Year-year let EmpAgeInMonthToday=DateTime.Now.Month-month let temp_year=(EmpAgeInYearsToday-1) let ExactNoOfMonths_temp=EmpAgeInMonthToday<0?temp_year:EmpAgeInMonthToday let ExactNoOfMonths=EmpAgeInMonthToday<0?EmpAgeInMonthToday+12&temp_year:EmpAgeInMonthToday select new{emp.EmployeeID,DOB, EmployeeAgeToday=EmpAgeInYearsToday+" Years "+ExactNoOfMonths+" Months ").Dump(); Here, let ExactNoOfMonths=EmpAgeInMonthToday<0?EmpAgeInMonthToday+12&temp_year:EmpAgeInMonthToday This part is not working. How to achieve this? How to perform multiple operations when the condition is satisfied?

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