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  • How to ignore blank elements in linq query

    - by Maestro1024
    How to ignore blank elements in linq query I have a linq query var usersInDatabase = from user in licenseUserTable where user.FirstName == first_name && user.LastName == last_name select user; But if I get here and first_name or last_name is blank then I want to still evaluate the other data item.

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  • Linq to SQL Repository ~theory~ - Generic but now uses Linq to Objects?

    - by Matt Tolliday
    The project I am currently working on used Linq to SQL as an ORM data access technology. Its an MVC3 Web app. The problem I faced was primarily due to the inability to mock (for testing) the DataContext which gets autogenerated by the DBML designer. So to solve this issue (after much reading) I refactored the repository system which was in place - single repository with seperate and duplicated access methods for each table which ended up with something like 300 methods only 10 of which were unique - into a single repository with generic methods taking the table and returning more generic types to the upper reaches of the application. My question revolves more around the design I've used to get thus far and the differences I'm noticing in the structure of the app. 1) Having refactored the code from the dark ages which used classic Linq to SQL queries: public Billing GetBilling(int id) { var result = ( from bil in _bicDc.Billings where bil.BillingId == id select bil).SingleOrDefault(); return (result); } it now looks like: public T GetRecordWhere<T>(Expression<Func<T, bool>> predicate) where T : class { T result; try { result = _dataContext.GetTable<T>().Where(predicate).SingleOrDefault(); } catch (Exception ex) { throw ex; } return result; } and is used by the controller with a query along the lines of: _repository.GetRecordWhere<Billing>(x => x.BillingId == 1); which is fine, and precisely what I wanted to achieve. ...however.... I'm also having to do the following to get precisely the result set i require in the controller class (the highest point of the app in essence)... viewModel.RecentRequests = _model.GetAllRecordsWhere<Billing>(x => x.BillingId == 1) .Where(x => x.BillingId == Convert.ToInt32(BillingType.Submitted)) .OrderByDescending(x => x.DateCreated). Take(5).ToList(); This - as far as my understanding is correct - is now using Linq to Objects rather than the Linq to SQL queries I was previously? Is this okay practise? It feels wrong to me but I dont know why. Probably because the logic of the queries is in the very highest tier of the app, rather than the lowest, but... I defer to you good people for advice. One of the issues I considered was bringing the entire table into memory but I understand that using the Iqeryable return type the where clause is taken to the database and evaluated there. Thus returning only the resultset i require... i may be wrong. And if you've made it this far, well done. Thank you, and if you have any advice it is very much appreciated!!

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  • Bash script throws, "syntax error near unexpected token `}'" when ran

    - by Tab00
    I am trying to write a script to monitor some battery statuses on a laptop running as a server. To accomplish this, I have already started to write this code: #! /bin/bash # A script to monitor battery statuses and send out email notifications #take care of looping the script for (( ; ; )) do #First, we check to see if the battery is present... if(cat /proc/acpi/battery/BAT0/state | grep 'present: *' == present: yes) { #Code to execute if battery IS present #No script needed for our application #you may add scripts to run } else { #if the battery IS NOT present, run this code sendemail -f [email protected] -t 214*******@txt.att.net -u NTA TV Alert -m "The battery from the computer is either missing, or removed. Please check ASAP." -s smtp.gmail.com -o tls=yes -xu [email protected] -xp *********** } #Second, we check into the current state of the battery if(cat /proc/acpi/battery/BAT0/state | grep 'charging state: *' == 'charging state: charging') { #Code to execute if battery is charging sendemail -f [email protected] -t 214*******@txt.att.net -u NTA TV Alert -m "The battery from the computer is charging. This MIGHT mean that something just happened" -s smtp.gmail.com -o tls=yes -xu [email protected] -xp *********** } #If it isn't charging, is it discharging? else if(cat /proc/acpi/battery/BAT0/state | grep 'charging state: *' == 'charging state: discharging') { #Code to run if the battery is discharging sendemail -f [email protected] -t 214*******@txt.att.net -u NTA TV Alert -m "The battery from the computer is discharging. This shouldn't be happening. Please check ASAP." -s smtp.gmail.com -o tls=yes -xu [email protected] -xp *********** } #If it isn't charging or discharging, is it charged? else if(cat /proc/acpi/battery/BAT0/state | grep 'charging state: *' == 'charging state: charged') { #Code to run if battery is charged } done I'm pretty sure that most of the other stuff works correctly, but I haven't been able to try it because it will not run. whenever I try and run the script, this is the error that I get: ./BatMon.sh: line 15: syntax error near unexpected token `}' ./BatMon.sh: ` }' is the error something super simple like a forgotten semicolon? Thanks -Tab00

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  • Building a common syntax and scoping framework.

    - by Ben DeMott
    Hello fellow programmers, I was discussing a project the other day with a colleague of mine and I was curious to see what others had to say or if such a thing already existed. Background There are many programming languages. There are many IDE's and source editors that highlight and edit source code. Following perfectly and exactly the rules of a language to present auto-complete options and understand scopes in the code is rather complex. This task is complex enough that most IDE's implement different source-editors as plugins that often re-implement the same features over and over but in a different way (netbeans). From what I can tell most IDE's and source editors re-implement parsers that use regular expressions, or some meta-syntax Naur Form to describe the languages grammer generically. These parsers are implemented over and over and over again. Question Has anyone attempted to unify or describe a set of features through an API and have a consistent interface to parsing various programming languages and dialects. I'm not describing an IDE - but a consistent API for any program to use to parse and obtain meta-information from the source code. I realize various programming languages offer many different features which are difficult to 'abstract' into a set of features, but I feel this would be a worthwhile venture. It seems to me that this could possibly allow the authors of interpreters to help maintain a central grammer intepreter for their language. the Python foundation could maintain the Python grammer api, ANSI the C grammer api, Oracle the Java grammer API, etc Example usage If this was API existed code documentation generators could theoretically work across all dialects and languages to some level. It wouldn't matter if your project used 5 different languages a single application could document all of them and the comments and doc-tags within. Has anyone attempted this comprehensively?

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  • Changes to the LINQ-to-StreamInsight Dialect

    - by Roman Schindlauer
    In previous versions of StreamInsight (1.0 through 2.0), CepStream<> represents temporal streams of many varieties: Streams with ‘open’ inputs (e.g., those defined and composed over CepStream<T>.Create(string streamName) Streams with ‘partially bound’ inputs (e.g., those defined and composed over CepStream<T>.Create(Type adapterFactory, …)) Streams with fully bound inputs (e.g., those defined and composed over To*Stream – sequences or DQC) The stream may be embedded (where Server.Create is used) The stream may be remote (where Server.Connect is used) When adding support for new programming primitives in StreamInsight 2.1, we faced a choice: Add a fourth variety (use CepStream<> to represent streams that are bound the new programming model constructs), or introduce a separate type that represents temporal streams in the new user model. We opted for the latter. Introducing a new type has the effect of reducing the number of (confusing) runtime failures due to inappropriate uses of CepStream<> instances in the incorrect context. The new types are: IStreamable<>, which logically represents a temporal stream. IQStreamable<> : IStreamable<>, which represents a queryable temporal stream. Its relationship to IStreamable<> is analogous to the relationship of IQueryable<> to IEnumerable<>. The developer can compose temporal queries over remote stream sources using this type. The syntax of temporal queries composed over IQStreamable<> is mostly consistent with the syntax of our existing CepStream<>-based LINQ provider. However, we have taken the opportunity to refine certain aspects of the language surface. Differences are outlined below. Because 2.1 introduces new types to represent temporal queries, the changes outlined in this post do no impact existing StreamInsight applications using the existing types! SelectMany StreamInsight does not support the SelectMany operator in its usual form (which is analogous to SQL’s “CROSS APPLY” operator): static IEnumerable<R> SelectMany<T, R>(this IEnumerable<T> source, Func<T, IEnumerable<R>> collectionSelector) It instead uses SelectMany as a convenient syntactic representation of an inner join. The parameter to the selector function is thus unavailable. Because the parameter isn’t supported, its type in StreamInsight 1.0 – 2.0 wasn’t carefully scrutinized. Unfortunately, the type chosen for the parameter is nonsensical to LINQ programmers: static CepStream<R> SelectMany<T, R>(this CepStream<T> source, Expression<Func<CepStream<T>, CepStream<R>>> streamSelector) Using Unit as the type for the parameter accurately reflects the StreamInsight’s capabilities: static IQStreamable<R> SelectMany<T, R>(this IQStreamable<T> source, Expression<Func<Unit, IQStreamable<R>>> streamSelector) For queries that succeed – that is, queries that do not reference the stream selector parameter – there is no difference between the code written for the two overloads: from x in xs from y in ys select f(x, y) Top-K The Take operator used in StreamInsight causes confusion for LINQ programmers because it is applied to the (unbounded) stream rather than the (bounded) window, suggesting that the query as a whole will return k rows: (from win in xs.SnapshotWindow() from x in win orderby x.A select x.B).Take(k) The use of SelectMany is also unfortunate in this context because it implies the availability of the window parameter within the remainder of the comprehension. The following compiles but fails at runtime: (from win in xs.SnapshotWindow() from x in win orderby x.A select win).Take(k) The Take operator in 2.1 is applied to the window rather than the stream: Before After (from win in xs.SnapshotWindow() from x in win orderby x.A select x.B).Take(k) from win in xs.SnapshotWindow() from b in     (from x in win     orderby x.A     select x.B).Take(k) select b Multicast We are introducing an explicit multicast operator in order to preserve expression identity, which is important given the semantics about moving code to and from StreamInsight. This also better matches existing LINQ dialects, such as Reactive. This pattern enables expressing multicasting in two ways: Implicit Explicit var ys = from x in xs          where x.A > 1          select x; var zs = from y1 in ys          from y2 in ys.ShiftEventTime(_ => TimeSpan.FromSeconds(1))          select y1 + y2; var ys = from x in xs          where x.A > 1          select x; var zs = ys.Multicast(ys1 =>     from y1 in ys1     from y2 in ys1.ShiftEventTime(_ => TimeSpan.FromSeconds(1))     select y1 + y2; Notice the product translates an expression using implicit multicast into an expression using the explicit multicast operator. The user does not see this translation. Default window policies Only default window policies are supported in the new surface. Other policies can be simulated by using AlterEventLifetime. Before After xs.SnapshotWindow(     WindowInputPolicy.ClipToWindow,     SnapshotWindowInputPolicy.Clip) xs.SnapshotWindow() xs.TumblingWindow(     TimeSpan.FromSeconds(1),     HoppingWindowOutputPolicy.PointAlignToWindowEnd) xs.TumblingWindow(     TimeSpan.FromSeconds(1)) xs.TumblingWindow(     TimeSpan.FromSeconds(1),     HoppingWindowOutputPolicy.ClipToWindowEnd) Not supported … LeftAntiJoin Representation of LASJ as a correlated sub-query in the LINQ surface is problematic as the StreamInsight engine does not support correlated sub-queries (see discussion of SelectMany). The current syntax requires the introduction of an otherwise unsupported ‘IsEmpty()’ operator. As a result, the pattern is not discoverable and implies capabilities not present in the server. The direct representation of LASJ is used instead: Before After from x in xs where     (from y in ys     where x.A > y.B     select y).IsEmpty() select x xs.LeftAntiJoin(ys, (x, y) => x.A > y.B) from x in xs where     (from y in ys     where x.A == y.B     select y).IsEmpty() select x xs.LeftAntiJoin(ys, x => x.A, y => y.B) ApplyWithUnion The ApplyWithUnion methods have been deprecated since their signatures are redundant given the standard SelectMany overloads: Before After xs.GroupBy(x => x.A).ApplyWithUnion(gs => from win in gs.SnapshotWindow() select win.Count()) xs.GroupBy(x => x.A).SelectMany(     gs =>     from win in gs.SnapshotWindow()     select win.Count()) xs.GroupBy(x => x.A).ApplyWithUnion(gs => from win in gs.SnapshotWindow() select win.Count(), r => new { r.Key, Count = r.Payload }) from x in xs group x by x.A into gs from win in gs.SnapshotWindow() select new { gs.Key, Count = win.Count() } Alternate UDO syntax The representation of UDOs in the StreamInsight LINQ dialect confuses cardinalities. Based on the semantics of user-defined operators in StreamInsight, one would expect to construct queries in the following form: from win in xs.SnapshotWindow() from y in MyUdo(win) select y Instead, the UDO proxy method is referenced within a projection, and the (many) results returned by the user code are automatically flattened into a stream: from win in xs.SnapshotWindow() select MyUdo(win) The “many-or-one” confusion is exemplified by the following example that compiles but fails at runtime: from win in xs.SnapshotWindow() select MyUdo(win) + win.Count() The above query must fail because the UDO is in fact returning many values per window while the count aggregate is returning one. Original syntax New alternate syntax from win in xs.SnapshotWindow() select win.UdoProxy(1) from win in xs.SnapshotWindow() from y in win.UserDefinedOperator(() => new Udo(1)) select y -or- from win in xs.SnapshotWindow() from y in win.UdoMacro(1) select y Notice that this formulation also sidesteps the dynamic type pitfalls of the existing “proxy method” approach to UDOs, in which the type of the UDO implementation (TInput, TOuput) and the type of its constructor arguments (TConfig) need to align in a precise and non-obvious way with the argument and return types for the corresponding proxy method. UDSO syntax UDSO currently leverages the DataContractSerializer to clone initial state for logical instances of the user operator. Initial state will instead be described by an expression in the new LINQ surface. Before After xs.Scan(new Udso()) xs.Scan(() => new Udso()) Name changes ShiftEventTime => AlterEventStartTime: The alter event lifetime overload taking a new start time value has been renamed. CountByStartTimeWindow => CountWindow

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  • Languages like Tcl that have configurable syntax?

    - by boost
    I'm looking for a language that will let me do what I could do with Clipper years ago, and which I can do with Tcl, namely add functionality in a way other than just adding functions. For example in Clipper/(x)Harbour there are commands #command, #translate, #xcommand and #xtranslate that allow things like this: #xcommand REPEAT; => DO WHILE .T. #xcommand UNTIL <cond>; => IF (<cond>); ;EXIT; ;ENDIF; ;ENDDO LOCAL n := 1 REPEAT n := n + 1 UNTIL n > 100 Similarly, in Tcl I'm doing proc process_range {_for_ project _from_ dat1 _to_ dat2 _by_ slice} { set fromDate [clock scan $dat1] set toDate [clock scan $dat2] if {$slice eq "day"} then {set incrementor [expr 24 * 60]} if {$slice eq "hour"} then {set incrementor 60} set method DateRange puts "Scanning from [clock format $fromDate -format "%c"] to [clock format $toDate -format "%c"] by $slice" for {set dateCursor $fromDate} {$dateCursor <= $toDate} {set dateCursor [clock add $dateCursor $incrementor minutes]} { # ... } } process_range for "client" from "2013-10-18 00:00" to "2013-10-20 23:59" by day Are there any other languages that permit this kind of, almost COBOL-esque, syntax modification? If you're wondering why I'm asking, it's for setting up stuff so that others with a not-as-geeky-as-I-am skillset can declare processing tasks.

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  • Changes to the LINQ-to-StreamInsight Dialect

    - by Roman Schindlauer
    In previous versions of StreamInsight (1.0 through 2.0), CepStream<> represents temporal streams of many varieties: Streams with ‘open’ inputs (e.g., those defined and composed over CepStream<T>.Create(string streamName) Streams with ‘partially bound’ inputs (e.g., those defined and composed over CepStream<T>.Create(Type adapterFactory, …)) Streams with fully bound inputs (e.g., those defined and composed over To*Stream – sequences or DQC) The stream may be embedded (where Server.Create is used) The stream may be remote (where Server.Connect is used) When adding support for new programming primitives in StreamInsight 2.1, we faced a choice: Add a fourth variety (use CepStream<> to represent streams that are bound the new programming model constructs), or introduce a separate type that represents temporal streams in the new user model. We opted for the latter. Introducing a new type has the effect of reducing the number of (confusing) runtime failures due to inappropriate uses of CepStream<> instances in the incorrect context. The new types are: IStreamable<>, which logically represents a temporal stream. IQStreamable<> : IStreamable<>, which represents a queryable temporal stream. Its relationship to IStreamable<> is analogous to the relationship of IQueryable<> to IEnumerable<>. The developer can compose temporal queries over remote stream sources using this type. The syntax of temporal queries composed over IQStreamable<> is mostly consistent with the syntax of our existing CepStream<>-based LINQ provider. However, we have taken the opportunity to refine certain aspects of the language surface. Differences are outlined below. Because 2.1 introduces new types to represent temporal queries, the changes outlined in this post do no impact existing StreamInsight applications using the existing types! SelectMany StreamInsight does not support the SelectMany operator in its usual form (which is analogous to SQL’s “CROSS APPLY” operator): static IEnumerable<R> SelectMany<T, R>(this IEnumerable<T> source, Func<T, IEnumerable<R>> collectionSelector) It instead uses SelectMany as a convenient syntactic representation of an inner join. The parameter to the selector function is thus unavailable. Because the parameter isn’t supported, its type in StreamInsight 1.0 – 2.0 wasn’t carefully scrutinized. Unfortunately, the type chosen for the parameter is nonsensical to LINQ programmers: static CepStream<R> SelectMany<T, R>(this CepStream<T> source, Expression<Func<CepStream<T>, CepStream<R>>> streamSelector) Using Unit as the type for the parameter accurately reflects the StreamInsight’s capabilities: static IQStreamable<R> SelectMany<T, R>(this IQStreamable<T> source, Expression<Func<Unit, IQStreamable<R>>> streamSelector) For queries that succeed – that is, queries that do not reference the stream selector parameter – there is no difference between the code written for the two overloads: from x in xs from y in ys select f(x, y) Top-K The Take operator used in StreamInsight causes confusion for LINQ programmers because it is applied to the (unbounded) stream rather than the (bounded) window, suggesting that the query as a whole will return k rows: (from win in xs.SnapshotWindow() from x in win orderby x.A select x.B).Take(k) The use of SelectMany is also unfortunate in this context because it implies the availability of the window parameter within the remainder of the comprehension. The following compiles but fails at runtime: (from win in xs.SnapshotWindow() from x in win orderby x.A select win).Take(k) The Take operator in 2.1 is applied to the window rather than the stream: Before After (from win in xs.SnapshotWindow() from x in win orderby x.A select x.B).Take(k) from win in xs.SnapshotWindow() from b in     (from x in win     orderby x.A     select x.B).Take(k) select b Multicast We are introducing an explicit multicast operator in order to preserve expression identity, which is important given the semantics about moving code to and from StreamInsight. This also better matches existing LINQ dialects, such as Reactive. This pattern enables expressing multicasting in two ways: Implicit Explicit var ys = from x in xs          where x.A > 1          select x; var zs = from y1 in ys          from y2 in ys.ShiftEventTime(_ => TimeSpan.FromSeconds(1))          select y1 + y2; var ys = from x in xs          where x.A > 1          select x; var zs = ys.Multicast(ys1 =>     from y1 in ys1     from y2 in ys1.ShiftEventTime(_ => TimeSpan.FromSeconds(1))     select y1 + y2; Notice the product translates an expression using implicit multicast into an expression using the explicit multicast operator. The user does not see this translation. Default window policies Only default window policies are supported in the new surface. Other policies can be simulated by using AlterEventLifetime. Before After xs.SnapshotWindow(     WindowInputPolicy.ClipToWindow,     SnapshotWindowInputPolicy.Clip) xs.SnapshotWindow() xs.TumblingWindow(     TimeSpan.FromSeconds(1),     HoppingWindowOutputPolicy.PointAlignToWindowEnd) xs.TumblingWindow(     TimeSpan.FromSeconds(1)) xs.TumblingWindow(     TimeSpan.FromSeconds(1),     HoppingWindowOutputPolicy.ClipToWindowEnd) Not supported … LeftAntiJoin Representation of LASJ as a correlated sub-query in the LINQ surface is problematic as the StreamInsight engine does not support correlated sub-queries (see discussion of SelectMany). The current syntax requires the introduction of an otherwise unsupported ‘IsEmpty()’ operator. As a result, the pattern is not discoverable and implies capabilities not present in the server. The direct representation of LASJ is used instead: Before After from x in xs where     (from y in ys     where x.A > y.B     select y).IsEmpty() select x xs.LeftAntiJoin(ys, (x, y) => x.A > y.B) from x in xs where     (from y in ys     where x.A == y.B     select y).IsEmpty() select x xs.LeftAntiJoin(ys, x => x.A, y => y.B) ApplyWithUnion The ApplyWithUnion methods have been deprecated since their signatures are redundant given the standard SelectMany overloads: Before After xs.GroupBy(x => x.A).ApplyWithUnion(gs => from win in gs.SnapshotWindow() select win.Count()) xs.GroupBy(x => x.A).SelectMany(     gs =>     from win in gs.SnapshotWindow()     select win.Count()) xs.GroupBy(x => x.A).ApplyWithUnion(gs => from win in gs.SnapshotWindow() select win.Count(), r => new { r.Key, Count = r.Payload }) from x in xs group x by x.A into gs from win in gs.SnapshotWindow() select new { gs.Key, Count = win.Count() } Alternate UDO syntax The representation of UDOs in the StreamInsight LINQ dialect confuses cardinalities. Based on the semantics of user-defined operators in StreamInsight, one would expect to construct queries in the following form: from win in xs.SnapshotWindow() from y in MyUdo(win) select y Instead, the UDO proxy method is referenced within a projection, and the (many) results returned by the user code are automatically flattened into a stream: from win in xs.SnapshotWindow() select MyUdo(win) The “many-or-one” confusion is exemplified by the following example that compiles but fails at runtime: from win in xs.SnapshotWindow() select MyUdo(win) + win.Count() The above query must fail because the UDO is in fact returning many values per window while the count aggregate is returning one. Original syntax New alternate syntax from win in xs.SnapshotWindow() select win.UdoProxy(1) from win in xs.SnapshotWindow() from y in win.UserDefinedOperator(() => new Udo(1)) select y -or- from win in xs.SnapshotWindow() from y in win.UdoMacro(1) select y Notice that this formulation also sidesteps the dynamic type pitfalls of the existing “proxy method” approach to UDOs, in which the type of the UDO implementation (TInput, TOuput) and the type of its constructor arguments (TConfig) need to align in a precise and non-obvious way with the argument and return types for the corresponding proxy method. UDSO syntax UDSO currently leverages the DataContractSerializer to clone initial state for logical instances of the user operator. Initial state will instead be described by an expression in the new LINQ surface. Before After xs.Scan(new Udso()) xs.Scan(() => new Udso()) Name changes ShiftEventTime => AlterEventStartTime: The alter event lifetime overload taking a new start time value has been renamed. CountByStartTimeWindow => CountWindow

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  • Using LINQ to SQL in ASP.NET MVC2 project

    - by mazhar
    Well I am new to this ORM stuff. We have to create a large project. I read about LINQ to SQL. will it be appropriate to use it in the project of high risk. i found no problem with it personally but the thing is that there will be no going back once started.So i need some feedback from the ORM gurus here at the MSDN. Will entity framework will be better? (I am in doubt about LINK to SQL because I have read and heard negative feedback here and there) I will be using MVC2 as the framework. So please give the feedback about LINQ to SQL in this regard. Q2) Also I am a fan of stored procedure as they are precomputed and fasten up the thing and I have never worked without them.I know that LINQ to SQL support stored procedures but will it be feasible to give up stored procedure seeing the beautiful data access layer generated with little effort as we are also in a need of rapid development. Q3) If some changes to some fields required in the database in LINK to SQL how will the changes be accommodated in the data access layer.

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  • Linq, Left Join and Dates...

    - by BitFiddler
    So my situation is that I have a linq-to-sql model that does not allow dates to be null in one of my tables. This is intended, because the database does not allow nulls in that field. My problem, is that when I try to write a Linq query with this model, I cannot do a left join with that table anymore because the date is not a 'nullable' field and so I can't compare it to "Nothing". Example: There is a Movie table, {ID,MovieTitle}, and a Showings table, {ID,MovieID,ShowingTime,Location} Now I am trying to write a statement that will return all those movies that have no showings. In T.SQL this would look like: Select m.* From Movies m Left Join Showings s On m.ID = s.MovieID Where s.ShowingTime is Null Now in this situation I could test for Null on the 'Location' field but this is not what I have in reality (just a simplified example). All I have are non-null dates. I am trying to write in Linq: From m In dbContext.Movies _ Group Join s In Showings on m.ID Equals s.MovieID into MovieShowings = Group _ From ms In MovieShowings.DefaultIfEmpty _ Where ms.ShowingTime is Nothing _ Select ms However I am getting an error saying 'Is' operator does not accept operands of type 'Date'. Operands must be reference or nullable types. Is there any way around this? The model is correct, there should never be a null in the Showings:ShowTime table. But if you do a left join, and there are no show times for a particular movie, then ShowTime SHOULD be Nothing for that movie... Thanks everyone for your help.

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  • Linq - how does it work??

    - by clarkeyboy
    Hey, I have just been looking into Linq with ASP.Net. It is very neat indeed. I was just wondering - how do all the classes get populated? I mean in ASP.Net, suppose you have a Linq file called Catalogue, and you then use a For loop to loop through Catalogue.Products and print each Product name. How do the details get stored? Does it just go through the Products table on page load and create another instance of class Product for each row, effectively copying an entire table into an array of class Product? If so, I think I have created a system very much like this, in the sense that there is a SiteContent module with an instance of each Manager class - for example there is UserManager, ProductManager, SettingManager and alike. UserManager contains an instance of the User class for each row in the Users table. They also contain methods such as Create, Update and Remove. These Managers and their "Items" are created on every page load. This just makes it nice and easy to access users, products, settings etc in every page as far as I, the developer, am concerned. Any any subsequent pages I need to create, I just need to reference SiteContent.UserManager to access a list of users, rather than executing a query from within that page (ie this method separates out data access from the workings of the page, in the same way as using code behind separates out the workings of the page from how the page is layed out). However the problem is that this technique seems rather slow. I mean it is effectively creating a database on every page load, taking data from another database. I have taken measures such as preventing, for example, the ProductManager from being created if it is not referenced on page load. Therefore it does not load data into storage when it is not needed. My question is basically whether my technique does the exact same thing as Linq, in the sense of duplicating data from tables into properties of classes.. Thanks in advance for any advice or answers about this. Regards, Richard Clarke

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  • LEFT OUTER JOIN in Linq - How to Force

    - by dodegaard
    I have a LEFT OUTER OUTER join in LINQ that is combining with the outer join condition and not providing the desired results. It is basically limiting my LEFT side result with this combination. Here is the LINQ and resulting SQL. What I'd like is for "AND ([t2].[EligEnd] = @p0" in the LINQ query to not bew part of the join condition but rather a subquery to filter results BEFORE the join. Thanks in advance (samples pulled from LINQPad) - Doug (from l in Users join mr in (from mri in vwMETRemotes where met.EligEnd == Convert.ToDateTime("2009-10-31") select mri) on l.Mahcpid equals mr.Mahcpid into lo from g in lo.DefaultIfEmpty() orderby l.LastName, l.FirstName where l.LastName.StartsWith("smith") && l.DeletedDate == null select g) Here is the resulting SQL -- Region Parameters DECLARE @p0 DateTime = '2009-10-31 00:00:00.000' DECLARE @p1 NVarChar(6) = 'smith%' -- EndRegion SELECT [t2].[test], [t2].[MAHCPID] AS [Mahcpid], [t2].[FirstName], [t2].[LastName], [t2].[Gender], [t2].[Address1], [t2].[Address2], [t2].[City], [t2].[State] AS [State], [t2].[ZipCode], [t2].[Email], [t2].[EligStart], [t2].[EligEnd], [t2].[Dependent], [t2].[DateOfBirth], [t2].[ID], [t2].[MiddleInit], [t2].[Age], [t2].[SSN] AS [Ssn], [t2].[County], [t2].[HomePhone], [t2].[EmpGroupID], [t2].[PopulationIdentifier] FROM [dbo].[User] AS [t0] LEFT OUTER JOIN ( SELECT 1 AS [test], [t1].[MAHCPID], [t1].[FirstName], [t1].[LastName], [t1].[Gender], [t1].[Address1], [t1].[Address2], [t1].[City], [t1].[State], [t1].[ZipCode], [t1].[Email], [t1].[EligStart], [t1].[EligEnd], [t1].[Dependent], [t1].[DateOfBirth], [t1].[ID], [t1].[MiddleInit], [t1].[Age], [t1].[SSN], [t1].[County], [t1].[HomePhone], [t1].[EmpGroupID], [t1].[PopulationIdentifier] FROM [dbo].[vwMETRemote] AS [t1] ) AS [t2] ON ([t0].[MAHCPID] = [t2].[MAHCPID]) AND ([t2].[EligEnd] = @p0) WHERE ([t0].[LastName] LIKE @p1) AND ([t0].[DeletedDate] IS NULL) ORDER BY [t0].[LastName], [t0].[FirstName]

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  • LINQ-to-SQL IN/Contains() for Nullable<T>

    - by Craig Walker
    I want to generate this SQL statement in LINQ: select * from Foo where Value in ( 1, 2, 3 ) The tricky bit seems to be that Value is a column that allows nulls. The equivalent LINQ code would seem to be: IEnumerable<Foo> foos = MyDataContext.Foos; IEnumerable<int> values = GetMyValues(); var myFoos = from foo in foos where values.Contains(foo.Value) select foo; This, of course, doesn't compile, since foo.Value is an int? and values is typed to int. I've tried this: IEnumerable<Foo> foos = MyDataContext.Foos; IEnumerable<int> values = GetMyValues(); IEnumerable<int?> nullables = values.Select( value => new Nullable<int>(value)); var myFoos = from foo in foos where nullables.Contains(foo.Value) select foo; ...and this: IEnumerable<Foo> foos = MyDataContext.Foos; IEnumerable<int> values = GetMyValues(); var myFoos = from foo in foos where values.Contains(foo.Value.Value) select foo; Both of these versions give me the results I expect, but they do not generate the SQL I want. It appears that they're generating full-table results and then doing the Contains() filtering in-memory (ie: in plain LINQ, without -to-SQL); there's no IN clause in the DataContext log. Is there a way to generate a SQL IN for Nullable types?

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  • Does NHibernate LINQ support ToLower() in Where() clauses?

    - by Daniel T.
    I have an entity and its mapping: public class Test { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual string Description { get; set; } } public class TestMap : EntityMap<Test> { public TestMap() { Id(x => x.Id); Map(x => x.Name); Map(x => x.Description); } } I'm trying to run a query on it (to grab it out of the database): var keyword = "test" // this is coming in from the user keyword = keyword.ToLower(); // convert it to all lower-case var results = session.Linq<Test> .Where(x => x.Name.ToLower().Contains(keyword)); results.Count(); // execute the query However, whenever I run this query, I get the following exception: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index Am I right when I say that, currently, Linq to NHibernate does not support ToLower()? And if so, is there an alternative that allows me to search for a string in the middle of another string that Linq to NHibernate is compatible with? For example, if the user searches for kap, I need it to match Kapiolani, Makapuu, and Lapkap.

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  • Is there a way to use Linq projections with extension methods

    - by Acoustic
    I'm trying to use AutoMapper and a repository pattern along with a fluent interface, and running into difficulty with the Linq projection. For what it's worth, this code works fine when simply using in-memory objects. When using a database provider, however, it breaks when constructing the query graph. I've tried both SubSonic and Linq to SQL with the same result. Thanks for your ideas. Here's an extension method used in all scenarios - It's the source of the problem since everything works fine without using extension methods public static IQueryable<MyUser> ByName(this IQueryable<MyUser> users, string firstName) { return from u in users where u.FirstName == firstName select u; } Here's the in-memory code that works fine var userlist = new List<User> {new User{FirstName = "Test", LastName = "User"}}; Mapper.CreateMap<User, MyUser>(); var result = (from u in userlist select Mapper.Map<User, MyUser>(u)) .AsQueryable() .ByName("Test"); foreach (var x in result) { Console.WriteLine(x.FirstName); } Here's the same thing using a SubSonic (or Linq to SQL or whatever) that fails. This is what I'd like to make work somehow with extension methods... Mapper.CreateMap<User, MyUser>(); var result = from u in new DataClasses1DataContext().Users select Mapper.Map<User, MyUser>(u); var final = result.ByName("Test"); foreach(var x in final) // Fails here when the query graph built. { Console.WriteLine(x.FirstName); } The goal here is to avoid having to manually map the generated "User" object to the "MyUser" domain object- in other words, I'm trying to find a way to use AutoMapper so I don't have this kind of mapping code everywhere a database read operation is needed: var result = from u in new DataClasses1DataContext().Users select new MyUser // Can this be avoided with AutoMapper AND extension methods? { FirstName = v.FirstName, LastName = v.LastName };

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  • LINQ Query Returning Multiple Copies Of First Result

    - by Mike G
    I'm trying to figure out why a simple query in LINQ is returning odd results. I have a view defined in the database. It basically brings together several other tables and does some data munging. It really isn't anything special except for the fact that it deals with a large data set and can be a bit slow. I want to query this view based on a long. Two sample queries below show different queries to this view. var la = Runtime.OmsEntityContext.Positions.Where(p => p.AccountNumber == 12345678).ToList(); var deDa = Runtime.OmsEntityContext.Positions.Where(p => p.AccountNumber == 12345678).Select(p => new { p.AccountNumber, p.SecurityNumber, p.CUSIP }).ToList(); The first one should hand back a List. The second one will be a list of anonymous objects. When I do these queries in entities framework the first one will hand me back a list of results where they're all exactly the same. The second query will hand me back data where the account number is the one that I queried and the other values differ. This seems to do this on a per account number basis, ie if I were to query for one account number or another all the Position objects for one account would have the same value (the first one in the list of Positions for that account) and the second account would have a set of Position objects that all had the same value (again, the first one in it's list of Position objects). I can write SQL that is in effect the same as either of the two EF queries. They both come back with results (say four) that show the correct data, one account number with different securities numbers. Why does this happen??? Is there something that I could be doing wrong so that if I had four results for the first query above that the first record's data also appears in the 2-4th's objects??? I cannot fathom what would/could be causing this. I've searched Google for all kinds of keywords and haven't seen anyone with this issue. We partial class out the Positions class for added functionality (smart object) and some smart properties. There are even some constructors that provide some view model type support. None of this is invoked in the request (I'm 99% sure of this). However, we do this same pattern all over the app. The only thing I can think of is that the mapping in the EDMX is screwy. Is there a way that this would happen if the "primary keys" in the EDMX were not in fact unique given the way the view is constructed? I'm thinking that the dev who imported this model into the EDMX let the designer auto select what would be unique. Any help would give a haggered dev some hope!

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  • Linq to XML query returining a list of strings

    - by objectsbinding
    Hi all, I have the following class public class CountrySpecificPIIEntity { public string Country { get; set; } public string CreditCardType { get; set; } public String Language { get; set; } public List<String> PIIData { get; set; } } I have the following XML that I want to query using Linq-to-xml and shape in to the class above <?xml version="1.0" encoding="utf-8" ?> <piisettings> <piifilter country="DE" creditcardype="37" language="ALL" > <filters> <filter>FIRSTNAME</filter> <filter>SURNAME</filter> <filter>STREET</filter> <filter>ADDITIONALADDRESSINFO</filter> <filter>ZIP</filter> <filter>CITY</filter> <filter>STATE</filter> <filter>EMAIL</filter> </filters> </piifilter> <piifilter country="DE" creditcardype="37" Language="en" > <filters> <filter>EMAIL</filter> </filters> </piifilter> </piisettings> I'm using the following query but I'm having trouble with the last attribute i.e. PIIList. var query = from pii in xmlDoc.Descendants("piifilter") select new CountrySpecificPIIEntity { Country = pii.Attribut("country").Value, CreditCardType = pii.Attribute("creditcardype").Value, Language = pii.Attribute("Language").Value, PIIList = (List<string>)pii.Elements("filters") }; foreach (var entity in query) { Debug.Write(entity.Country); Debug.Write(entity.CreditCardType); Debug.Write(entity.Language); Debug.Write(entity.PIIList); } How Can I get the query to return a List to be hydrated in to the PIIList property.

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  • LINQ self referencing query

    - by Chris
    I have the following SQL query: select p1.[id], p1.[useraccountid], p1.[subject], p1.[message], p1.[views], p1.[parentid], case when p2.[created] is null then p1.[created] else p2.[created] end as LastUpdate from forumposts p1 left join ( select parentid, max(created) as [created] from forumposts group by parentid ) p2 on p2.parentid = p1.id where p1.[parentid] is null order by LastUpdate desc Using the following class: public class ForumPost : PersistedObject { public int Views { get; set; } public string Message { get; set; } public string Subject { get; set; } public ForumPost Parent { get; set; } public UserAccount UserAccount { get; set; } public IList<ForumPost> Replies { get; set; } } How would I replicate such a query in LINQ? I've tried several variations, but I seem unable to get the correct join syntax. Is this simply a case of a query that is too complicated for LINQ? Can it be done using nested queries some how? The purpose of the query is to find the most recently updated posts i.e. replying to a post would bump it to the top of the list. Replies are defined by the ParentID column, which is self-referencing.

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  • Advanced Linq query using into

    - by dilbert789
    I have this query that someone else wrote, it's over my head so I'm looking for some direction. What is happening currently is that it's taking numbers where there is a goal and no history entered, or history and no goal, this screws up the calculations as both goal and history for the same item are required on each. The three tables involved are: KPIType Goal KPIHistory What I need: Need all rows from KPIType. Need all goals where there is a matching KPIHistory row (Goal.KPItypeID == KPIHistory.KPItypeID ) into results 1 Need all kpiHistory’s where there is a matching Goal row (Goal.KPItypeID == KPIHistory.KPItypeID ) into results 2 Current query: var query = from t in dcs.KPIType.Where(k => k.ID <= 23) join g in dcs.Goal.Where(g => g.Dealership.ID == dealershipID && g.YearMonth >= beginDate && g.YearMonth <= endDate ) on t.ID equals g.KPITypeID into results1 join h in dcs.KPIHistory.Where(h => h.Dealership.ID == dealershipID && h.ForDate >= beginDate && h.ForDate <= endDate ) on t.ID equals h.KPIType.ID into results2 orderby t.DisplayOrder select new { t, Goal = results1, KPIHistory = results2 }; query.ToList().ForEach(q => { results.Add(q.t); }); Thanks, I'm happy to answer questions if more info needed.

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  • LINQ : How to query how to sort result by most similarity/equality

    - by aNui
    I want to do a search for Music instruments which has its informations Name, Category and Origin as I asked in my post. But now I want to sort/group the result by similarity/equality to the keyword such as. If I have the list { Harp, Piano, Drum, Guitar, Guitarrón } and if I queried "p" the result should be { Piano, Harp } but it shows Harp first because of the list's sequence and if I add {Grand Piano} to the list and query "piano" the result shoud be like { Piano, Grand Piano } here's my code static IEnumerable<MInstrument> InstrumentsSearch(IEnumerable<MInstrument> InstrumentsList, string query, MInstrument.Category[] SelectedCategories, MInstrument.Origin[] SelectedOrigins) { var result = InstrumentsList .Where(item => SelectedCategories.Contains(item.category)) .Where(item => SelectedOrigins.Contains(item.origin)) .Where(item => { if ( (" " + item.Name.ToLower()).Contains(" " + query.ToLower()) || item.Name.IndexOf(query) != -1 ) { return true; } return false; } ) .Take(30); return result.ToList<MInstrument>(); } Or the result may be like my old self-invented algorithm that I called "by order of occurence", that is just OK to me. Is there any way to do that, please tell me. Thanks in advance.

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  • LINQ To SQL exception: Local sequence cannot be used in LINQ to SQL implementation of query operator

    - by pcampbell
    Consider this LINQ To SQL query. It's intention is to take a string[] of search terms and apply the terms to a bunch of different fields on the SQL table: string[] searchTerms = new string[] {"hello","world","foo"}; List<Cust> = db.Custs.Where(c => searchTerms.Any(st => st.Equals(c.Email)) || searchTerms.Any(st => st.Equals(c.FirstName)) || searchTerms.Any(st => st.Equals(c.LastName)) || searchTerms.Any(st => st.Equals(c.City)) || searchTerms.Any(st => st.Equals(c.Postal)) || searchTerms.Any(st => st.Equals(c.Phone)) || searchTerms.Any(st => c.AddressLine1.Contains(st)) ) .ToList(); An exception is raised: Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator Question: Why is this exception raised, and how can the query be rewritten to avoid this exception?

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  • C#: Fill DataGridView From Anonymous Linq Query

    - by mdvaldosta
    // From my form BindingSource bs = new BindingSource(); private void fillStudentGrid() { bs.DataSource = Admin.GetStudents(); dgViewStudents.DataSource = bs; } // From the Admin class public static List<Student> GetStudents() { DojoDBDataContext conn = new DojoDBDataContext(); var query = (from s in conn.Students select new Student { ID = s.ID, FirstName = s.FirstName, LastName = s.LastName, Belt = s.Belt }).ToList(); return query; } I'm trying to fill a datagridview control in Winforms, and I only want a few of the values. The code compiles, but throws a runtime error: Explicit construction of entity type 'DojoManagement.Student' in query is not allowed. Is there a way to get it working in this manner?

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