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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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• 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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• 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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• Does LINQ to Objects caching?

  - by Raj Aththanayake

  Does LINQ to Objects queries cache by LINQ provider when it execute for the second time?

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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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• 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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• 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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• 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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• What Should I know to underestand LINQ better?

  - by Nasser Hajloo

  As LINQ is a good query language in dot net and everyone should be able to work with it. What are the necessary abilities which a programmer should have, before start learning LINQ. And after that, What should he know about LINQ? (important tips)

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• Using Three Flavors of LINQ To Populate a TreeView

  LINQ is a valuable technology. LINQ to XML, LINQ to Objects and LINQ to XSD, in particular, can save valuable time for developers and produce more maintainable code. Michael describes how he used three different flavours of LINQ to map XML to a Treeview component that he used in the QueryPicker control that was the subject of a two-part article here on Simple-Talk.

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• Download LINQPad to learn LINQ

  - by Editor

  LINQPad lets you interactively query SQL databases in a modern query language: LINQ. Say goodbye to SQL Management Studio.LINQPad supports everything in C# 3.0 and Framework 3.5: LINQ to SQL LINQ to Objects LINQ to XML LINQPad is also a great way to learn LINQ: it comes preloaded with 200 examples from the book, C# [...]

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• Converting LINQ to Twitter to Twitter API v1.1

  - by Joe Mayo

  Twitter recently updated their API to v1.1 (Current status: API v1.1). Naturally, LINQ to Twitter  needed to be updated too. This blog post outlines the changes made to LINQ to Twitter during this conversion and highlights important features that LINQ to Twitter developers will want to know. Overall Impact Generally speaking, Twitter API v1.1 is semantically very much the same as it’s predecessor. The base URL changed and so did a few resource segments, but the resources themselves are still intact. The good news is that LINQ to Twitter has always shielded the developer from this plumbing, so the entities, types, and filters didn’t change much at all.  The following sections describe what did  change. Authentication In Twitter API v1.0 authentication was not required for some resources, such as user timelines and search. However, that’s all changed because *all* queries must be authenticated in Twitter API v1.1. LINQ to Twitter has various types of authorizers you can use, supporting whatever OAuth options are available via Twitter.  You can see the LINQ to Twitter documentation, Securing Your Applications, for more info on OAuth support. The New Search One of the larger changes to the API was Search. To be more specific, the Search entity now contains a List<Status>, named Statuses, to hold results.  Additionally, any meta-data associated with the search is now in a property named SearchMetaData. The change to the Search entity and responses is the big change, but the good news is that your Search query syntax doesn’t change. Different Rate Limits The issue of rate limits itself is contentious, but this discussion is focused on the coding experience and I’ll leave the politics to those who prefer to engage in that activity. What’s important here is that both headers and resources have changed. You should review Twitter’s Rate Limit documentation to understand what the changes mean.  A quick explanation is that rate limits are applied individually to each resource in 15 minute time intervals. In LINQ to Twitter these changes surface on the Help entity, via HelpType.RateLimits. The RateLimits query has a Resources filter where you can specify a comma-separated list of categories to return rate limit info for.  The results materialize in the RateLimits dictionary, keyed on category. The Help entity also has a RateLimitsAuthorizationContext, holding the Access Token for the user performing queries – and to whom the rate limits apply. In addition to the new RateLimits query, there are new RateLimit headers that appear in the query response, whose HTTP header name is of the form X-Rate-Limit… which is different from the previous header name. LINQ to Twitter surfaces these headers via the existing properties of the TwitterContext instance. For anyone who retrieved rate limit information via the Headers property of TwitterContext, you should be aware of the new header names.  I haven’t done anything with Feature rate limit properties yet, but they appear to no longer be available – this will require more follow-up. Error Handling Twitter API v1.1 has a new format for Error Codes & Responses. LINQ to Twitter wraps these messages in the TwitterQueryException, which has been updated appropriately. The Message property of TwitterQueryException now reflects the Twitter error message, when available. There’s also a new ErrorCode that’s populated with the message error code. Parameters Most parameters stayed the same, but one of interest is Include Entities (different from LINQ to Twitter data object entities). Entities are metadata hanging off tweets, that provide start/end position in the tweet and other information for mentions, urls, hash tags, and media. Entities used to not be included unless you specified you wanted them. Now, in v1.1, entities are included by default for all APIs that return a Status.  If you were always setting IncludeEntities to true, then you won’t see a change. However, be aware that you’ll now be receiving additional data in your response from Twitter, which will explain a sudden increase in bandwidth utilization. This might or might not  matter to you  depending on the requirements of your application, but you should be aware of it. Everything Else There might be small changes here and there that I haven’t mentioned, but these were the ones you should be most aware of.  Streams didn’t change, but Twitter will be deprecating username/password authentication on public streams, in favor of OAuth, so you’ll be seeing me make that change some time in the future.  Also, Twitter will continue to evolve the API and you can expect that LINQ to Twitter will change accordingly. Summary The big changes to Twitter API were Authentication, Search, Rate Limits, and Error Handling. All API calls must be authenticated. You’ll need to change your code to read Search results differently, but the query is much the same as you use now. There’s a new RateLimits API, one of the Help queries.  Also, the new error messages are integrated into TwitterQueryException. Besides these changes, I expect  most others to be small or affect a smaller percentage of developers.  You can get the latest version of LINQ to Twitter from NuGet or visit the LINQ to Twitter download page at CodePlex.com.   @JoeMayo

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• C# LINQ Where Predicate Type Arguments

  - by blu

  I have an XElement with values for mock data. I have an expression to query the xml: Expression<Func<XElement, bool>> simpleXmlFunction = b => int.Parse(b.Element("FooId").Value) == 12; used in: var simpleXml = xml.Elements("Foo").Where(simpleXmlFunction).First(); The design time error is: The type arguments for method 'System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly' The delegate supplied to Where should take in an XElement and return a bool, marking if the item matches the query, I am not sure how to add anything more to the delegate or the where clause to mark the type. Also, the parallel method for the real function against the Entity Framework does not have this issue. What is not correct with the LINQ-to-XML version?

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• What’s New in Delphi XE6 Regular Expressions

  - by Jan Goyvaerts

  There’s not much new in the regular expression support in Delphi XE6. The big change that should be made, upgrading to PCRE 8.30 or later and switching to the pcre16 functions that use UTF-16, still hasn’t been made. XE6 still uses PCRE 7.9 and thus continues to require conversion from the UTF-16 strings that Delphi uses natively to the UTF-8 strings that older versions of PCRE require. Delphi XE6 does fix one important issue that has plagued TRegEx since it was introduced in Delphi XE. Previously, TRegEx could not find zero-length matches. So a regex like (?m)^ that should find a zero-length match at the start of each line would not find any matches at all with TRegEx. The reason for this is that TRegEx uses TPerlRegEx to do the heavy lifting. TPerlRegEx sets its State property to [preNotEmpty] in its constructor, which tells it to skip zero-length matches. This is not a problem with TPerlRegEx because users of this class can change the State property. But TRegEx does not provide a way to change this property. So in Delphi XE5 and prior, TRegEx cannot find zero-length matches. In Delphi XE6 TPerlRegEx’s constructor was changed to initialize State to the empty set. This means TRegEx is now able to find zero-length matches. TRegex.Replace() using the regex (?m)^ now inserts the replacement at the start of each line, as you would expect. If you use TPerlRegEx directly, you’ll need to set State to [preNotEmpty] in your own code if you relied on its behavior to skip zero-length matches. You will need to check existing applications that use TRegEx for regular expressions that incorrectly allow zero-length matches. In XE5 and prior, TRegEx using \d* would match all numbers in a string. In XE6, the same regex still matches all numbers, but also finds a zero-length match at each position in the string. RegexBuddy 4 warns about zero-length matches on the Create panel if you set it to Detailed mode. At the bottom of the regex tree there will be a node saying either “your regular expression may find zero-length matches” or “zero-length matches will be skipped” depending on whether your application allows zero-length matches (XE6 TRegEx) or not (XE–XE5 TRegEx).

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• Database and logic layer for ASP.NET MVC application

  - by Ismail

  I'm going to start a new project which is going to be small initially but may grow to big over the years. I'm strongly convinced that I'm going to use ASP.NET MVC with jQuery for UI. I want to go for MySQL as database for some reasons but worried on few things. I've a good years of experience working on SQL Server databases and on one project I've had a bad experience creating and managing stored procedures on MySQL database. I'm totally new to Linq but I see that it is easier to use once you are familiar with it. First thing is that accessing data should be easy. So I thought I should use MySQL to Linq but somewhere I read that it is not directly supported but MySQL .NET connector adds support for EntityFramework. I don't know what are the pros and cons of it. I would love if I can implement repository pattern as it allows to apply filter in logic layer rather than in data access layer. Will it be possible if I use Entity Framework? I'm not clear on how I should go about all this or I should just forget every thing and directly use SQL to Linq on SQL Server. I'm also concerned about the performance. Someone told me that if we use Entity framework it fetches lot of data and then filter it. Is that right? So questions basically are - Is MySQL to Linq possible? If yes where can I get more details on it? Pros and cons of using EntityFramework with MySQL? Will it be easy to access data using EntityFramework with MySQL? Will I be able to implement repository patter which allows applying filter in logic layer rather than data access layer (when I use EntityFramework with MySQL) Does it fetches hell lot of data from database and then apply filter on it? If it sounds too many questions from my side in that case, if you can just let me know what you will do (with a considerable reason) in this situation as an experienced person in this area, that should answer my question.

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• Properly handling possible System.NullReferenceException in lambda expressions

  - by Travis Johnson

  Here's the query in question return _projectDetail.ExpenditureDetails .Where(detail => detail.ProgramFund == _programFund && detail.Expenditure.User == _creditCardHolder) .Sum(detail => detail.ExpenditureAmounts.FirstOrDefault( amount => amount.isCurrent && !amount.requiresAudit) .CommittedMonthlyRecord.ProjectedEac); Table Structure ProjectDetails (1 to Many) ExpenditureDetails ExpenditureDetails (1 to Many) ExpenditureAmounts ExpenditureAmounts (1 to 1) CommittedMonthlyRecords ProjectedEac is a decimal field on the CommittedMonthlyRecords. The problem I discovered in a Unit test (albeit an unlikely event), that the following line could be null: detail.ExpenditureAmounts.FirstOrDefault( amount => amount.isCurrent && !amount.requiresAudit) My original query was a nested loop, in where I would be making multiple trips to the database, something I don't want to repeat. I've looked in to what seemed like some similar questions here, but the solution didn't seem to fit. Any ideas?

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• Linq DateTime expressions wont compare if only one is nullable

  - by tigermain

  I have been getting the following exception: The binary operator GreaterThanOrEqual is not defined for the types 'System.Nullable`1[System.DateTime]' and 'System.DateTime'. I am getting the left hand expression from a class property which is a nullable datetime variable and my right hand side is using Expression.Constant(new Nullable<DateTime>(DateTime.Now)) However I still get the above exception despite explicitly setting the right hand expression to a nullable type

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• Lambda expressions and nullable types

  - by Mathew

  I have two samples of code. One works and returns the correct result, one throws a null reference exception. What's the difference? I know there's some magic happening with capturing variables for the lambda expression but I don't understand what's going on behind the scenes here. int? x = null; bool isXNull = !x.HasValue; // this works var result = from p in data.Program where (isXNull) select p; return result.Tolist(); // this doesn't var result2 = from p in data.Program where (!x.HasValue) select p; return result2.ToList();

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• ASP.NET MVC 2: Updating a Linq-To-Sql Entity with an EntitySet

  - by Simon

  I have a Linq to Sql Entity which has an EntitySet. In my View I display the Entity with it's properties plus an editable list for the child entites. The user can dynamically add and delete those child entities. The DefaultModelBinder works fine so far, it correctly binds the child entites. Now my problem is that I just can't get Linq To Sql to delete the deleted child entities, it will happily add new ones but not delete the deleted ones. I have enabled cascade deleting in the foreign key relationship, and the Linq To Sql designer added the "DeleteOnNull=true" attribute to the foreign key relationships. If I manually delete a child entity like this: myObject.Childs.Remove(child); context.SubmitChanges(); This will delete the child record from the DB. But I can't get it to work for a model binded object. I tried the following: // this does nothing public ActionResult Update(int id, MyObject obj) // obj now has 4 child entities { var obj2 = _repository.GetObj(id); // obj2 has 6 child entities if(TryUpdateModel(obj2)) //it sucessfully updates obj2 and its childs { _repository.SubmitChanges(); // nothing happens, records stay in DB } else ..... return RedirectToAction("List"); } and this throws an InvalidOperationException, I have a german OS so I'm not exactly sure what the error message is in english, but it says something along the lines of that the entity needs a Version (Timestamp row?) or no update check policies. I have set UpdateCheck="Never" to every column except the primary key column. public ActionResult Update(MyObject obj) { _repository.MyObjectTable.Attach(obj, true); _repository.SubmitChanges(); // never gets here, exception at attach } I've read alot about similar "problems" with Linq To Sql, but it seems most of those "problems" are actually by design. So am I right in my assumption that this doesn't work like I expect it to work? Do I really have to manually iterate through the child entities and delete, update and insert them manually? For such a simple object this may work, but I plan to create more complex objects with nested EntitySets and so on. This is just a test to see what works and what not. So far I'm disappointed with Linq To Sql (maybe I just don't get it). Would be the Entity Framework or NHibernate a better choice for this scenario? Or would I run into the same problem?

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• Proper way to use Linq with WPF

  - by Ingó Vals

  I'm looking for a good guide into the right method of using Linq to Sql together with WPF. Most guides only go into the bare basics like how to show data from a database but noone I found goes into how to save back to the database. Can you answer or point out to me a guide that can answer these questions. I have a separate Data project because the same data will also be used in a web page so I have the repository method. That means I have a seperate class that uses the DataContext and there are methods like GetAllCompanies() and GetCompanyById ( int id ). 1) Where there are collections is it best to return as a IQueryable or should I return a list? Inside the WPF project I have seen reccomendations to wrap the collection in a ObservabgleCollection. 2) Why should I use ObservableCollection and should I use it even with Linq / IQueryable Some properties of the linq entities should be editable in the app so I set them to two-way mode. That would change the object in the observableCollection. 3) Is the object in the ObservableCollection still a instance of the original linq entity and so is the change reflected in the database ( when submitchanges is called ) I should have somekind of save method in the repository. But when should I call it? What happens if someone edits a field but decides not to save it, goes to another object and edits it and then press save. Doesn't the original change also save? When does it not remember the changes to a linq entity object anymore. Should I instance the Datacontext class in each method so it loses scope when done. 4) When and how to call the SubmitChanges method 5) Should I have the DataContext as a member variable of the repository class or a method variable To add a new row I should create a new object in a event ( "new" button push ) and then add it to the database using a repo method. 6) When I add the object to the database there will be no new object in the ObservableCollection. Do I refresh somehow. 7) I wan't to reuse the edit window when creating new but not sure how to dynamically changing from referencing selected item from a listview to this new object. Any examples you can point out.

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• Access the value of a member expression

  - by Schotime

  If i have a product. var p = new Product { Price = 30 }; and i have the following linq query. var q = repo.Products().Where(x=>x.Price == p.Price).ToList() In an IQueryable provider, I get a MemberExpression back for the p.Price which contains a Constant Expression, however I can't seem to get the value "30" back from it. Cheers.

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• c# Lambda Expression built with LinqKit does not compile

  - by Frank Michael Kraft

  This lambda does not compile, but I do not understand why. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Linq.Expressions; using LinqKit; namespace ConsoleApplication2 { class Program { static void Main(string[] args) { var barModel = new BarModel(); string id = "some"; Console.WriteLine(barModel.subFor(id).ToString()); // output: m => (True AndAlso (m.key == value(ConsoleApplication2.Bar`1+<>c__DisplayClass0[ConsoleApplication2.Model]).id)) Console.ReadKey(); var subworkitems = barModel.list.Where(barModel.subFor(id).Compile()); // Exception {"variable 'm' of type 'ConsoleApplication2.Model' referenced from scope '', but it is not defined"} Console.WriteLine(subworkitems.ToString()); Console.ReadKey(); } } class Bar<TModel> { public Bar(Expression<Func<TModel, string>> foreignKeyExpression) { _foreignKeyExpression = foreignKeyExpression; } private Expression<Func<TModel, string>> _foreignKeyExpression { get; set; } public Expression<Func<TModel, bool>> subFor(string id) { var ex = forTargetId(id); return ex; } public Expression<Func<TModel, bool>> forTargetId(String id) { var fc = _foreignKeyExpression; Expression<Func<TModel, bool>> predicate = m => true; var result = predicate.And(m => fc.Invoke(m) == id).Expand(); return result; } } class Model { public string key; public string value; } class BarModel : Bar<Model> { public List<Model> list; public BarModel() : base(m => m.key) { list = new List<Model>(); } } }

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