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  • LINQ TO SQL, Dynamic query with DATE type fields

    - by acanthus
    Hello, I'm building a query with the LINQ dynamic library so I don't know how many potential parameters will I have and I get an error when trying to query DATE type fields: Operator '=' incompatible with operand types 'DateTime' and 'String' When I step through the debugger in the Dynamic.cs it shows that the value is of type string and the field is of type date so the problem is obvious but I have no idea how to approach it. Any ideas? BR

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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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  • 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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  • LINQ compiled query DataBind issue

    - by Brian
    Hello All, I have a pretty extensive reporting page that uses LINQ. There is one main function that returns an IQueryable object. I then further filter / aggregate the returned query depending on the report the user needs. I changed this function to a compiled query, it worked great, and the speed increase was astonishing. The only problem comes when i want to databind the results. I am databinding to a standard asp.net GridView and it works fine, no problems. I am also databinding to an asp.net chart control, this is where my page is throwing an error. this works well: GridView gv = new GridView(); gv.DataSource = gridSource; But this does not: Series s1 = new Series("Series One"); s1.Points.DataBindXY(gridSource, "Month", gridSource, "Success"); The error i receive is this: System.NotSupportedException Specified method is not supported When i look into my gridSource var at run time i see this using a typical linq query: SELECT [t33].[value2] AS [Year], [t33].[value22] AS [Month], [t33].[value3] AS [Calls]...... I see this after i change the query to compiled: {System.Linq.OrderedEnumerable<<>f__AnonymousType15<string,int,int,int,int,int,int,int>,string>} This is obviously the reason why the databindxy is no longer working, but i am not sure how to get around it. Any help would be appreciated! Thanks

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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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  • Using Dynamic LINQ to get a filter for my Web API

    - by Espo
    We are considering using the Dynamic.CS linq-sample included in the "Samples" directory of visual studio 2008 for our WebAPI project to allow clients to query our data. The interface would be something like this (In addition to the normal GET-methods): public HttpResponseMessage List(string filter = null); The plan is to use the dynamic library to parse the "filter"-variable and then execute the query agains the DB. Any thoughts if this is a good idea? Is it a security problem?

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  • Tools to partition dynamic disk

    - by rangalo
    Hi, I have a 1 TB hard-disk with windows 7 pre-installed. I would like to delete, resize some partition and create ext3/swap partitions to install linux. Which tools are available for this ? I tried gparted, it doesn't work.

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  • Linq to XML - update/alter the nodes of an XML Document

    - by knox
    Hello! If got 2 Questions: 1. I've sarted working around with Linq to XML and i'm wondering if it is possible to change a XML document via Linq. I mean, is there someting like XDocument xmlDoc = XDocument.Load("sample.xml"); update item in xmlDoc.Descendants("item") where (int)item .Attribute("id") == id ... 2. I already know how to create and add a new XMLElement by simply using xmlDoc.Element("items").Add(new XElement(......); but how can i remove a single entry. XML sample data: <items> <item id="1" name="sample1" info="sample1 info" web="" /> <item id="2" name="sample2" info="sample2 info" web="" /> </itmes>

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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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  • Check username and password in LINQ query

    - by b0x0rz
    this linq query var users = from u in context.Users where u.UserEMailAdresses.Any(e1 => e1.EMailAddress == userEMail) && u.UserPasswords.Any(e2 => e2.PasswordSaltedHash == passwordSaltedHash) select u; return users.Count(); returns: 1 even when there is nothing in password table. how come? what i am trying to do is get the values of email and passwordHash from two separate tables (UserEMailAddresses and UserPasswords) linked via foreign keys to the third table (Users). it should be simple - checking if email and password mach from form to database. but it is not working for me. i get 1 (for count) even when there are NO entries in the UserPasswords table. is the linq query above completely wrong, or...?

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  • Entity LINQ on many-to-many got error "LINQ to Entities does not recognize the method 'Boolean Conta

    - by user300992
    I have 2 tables (Users and Roles) they are mapped as Many-to-Many in relational db. When I imported to Entity Data Content, they are still staying as the same relationship. Since they are mapped as Many-To-Many in Entity, I can access Users.RoleCollection or Roles.UserCollection However, when I execute this LINQ query, I got "LINQ to Entities does not recognize the method 'Boolean Contains... method, and this method cannot be translated into a store expression." var result (from a in Users from b in Roles where a.RoleCollection.Contains(b) select a); I think I must did something wrong... please help.

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  • help converting sql to linq expression with count

    - by Philip
    I am trying to convert the following SQL into a LINQ expression SELECT COUNT(ID) AS Count, MyCode FROM dbo.Archive WHERE DateSent=@DateStartMonth AND DateSent<=@DateEndMonth GROUP BY MyCode and I have been trying to follow this webpage as an example http://stackoverflow.com/questions/606124/converting-sql-containing-top-count-group-and-order-to-linq-2-entities I got this so far but I am stuck on understanding the new part var res=(from p in db.Archives where (p.DateSent>= dateStartMonth) && (p.DateSent< dateToday) group p by p.MyCode into g select new { ??????MyCode = g.something?, MonthlyCount= g.Count() }); Thanks in advance for helping greatly appreciated Philip

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  • Linq to SQL problem

    - by Ronnie Overby
    I have a local collection of recordId's (integers). I need to retrieve records that have every one of their child records' ids in that local collection. Here is my query: public List<int> OwnerIds { get; private set; } ... filteredPatches = from p in filteredPatches where OwnerIds.All(o => p.PatchesOwners.Select(x => x.OwnerId).Contains(o)) select p; I am getting this error: Local sequence cannot be used in Linq to SQL implementation of query operators except the Contains() operator. I get that .All() isn't supported by Linq to SQL, but is there a way to do what I am trying to do?

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  • How to Add Serialized LINQ to SQL Entities to a Word 2007 Document

    - by Ryan Riley
    I built a template-based document generator using the Open XML SDK (1.0), the Word 2007 Content Control Toolkit and LINQ to SQL (using the CodeSmith PLINQO templates). To do this, I serialized the LINQ to SQL entities to XML by retrieving the entity using DataLoadOptions specified in the source code. This works great, except that to initially populate the XML in my template, I currently have to copy and paste the XML from the Immediate window in VS2008 into the Content Control Toolkit, and it still has all the data from the current entity. I'm looking for two solutions: 1) Is this a good way to build a document generator with Word 2007? 1) How can I generate just the XML I need without the data? I've thought of creating an XSD and then creating an empty XML document, but wasn't sure how to do that programatically so that a business user can get the XML for the template. (That's not a requirement, just a nice-to-have.) Thanks for your feedback, Ryan

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  • LINQ query checks for null

    - by user300992
    I have a userList, some users don't have a name (null). If I run the first LINQ query, I got an error saying "object reference not set to an instance of an object" error. var temp = (from a in userList where ((a.name == "john") && (a.name != null)) select a).ToList(); However, if I switch the order by putting the checking for null in front, then it works without throwing any error: var temp = (from a in userList where ((a.name != null) && (a.name == "john")) select a).ToList(); Why is that? If that's pure C# code (not LINQ), I think both would be the same. I don't have SQL profiler, I am just curious what will be the difference when they are being translated on SQL level.

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  • How to dynamically choose two fields from a Linq query as a result

    - by Dr. Zim
    If you have a simple Linq query like: var result = from record in db.Customer select new { Text = record.Name, Value = record.ID.ToString() }; which is returning an object that can be mapped to a Drop Down List, is it possible to dynamically specify which fields map to Text and Value? Of course, you could do a big case (switch) statement, then code each Linq query separately but this isn't very elegant. What would be nice would be something like: (pseudo code) var myTextField = db.Customer["Name"]; // Could be an enumeration?? var myValueField = db.Customer["ID"]; // Idea: choose the field outside the query var result = from record in db.Customer select new { Text = myTextField, Value = myValueField };

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