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  • LinqKit stack overflow exception using predicate builder

    - by MLynn
    I am writing an application in C# using LINQ and LINQKit. I have a very large database table with company registration numbers in it. I want to do a LINQ query which will produce the equivalent SQL: select * from table1 where regno in('123','456') The 'in' clause may have thousands of terms. First I get the company registration numbers from a field such as Country. I then add all the company registration numbers to a predicate: var predicate = PredicateExtensions.False<table2>(); if (RegNos != null) { foreach (int searchTerm in RegNos) { int temp = searchTerm; predicate = predicate.Or(ec => ec.regno.Equals(temp)); } } On Windows Vista Professional a stack overflow exception occured after 4063 terms were added. On Windows Server 2003 a stack overflow exception occured after about 1000 terms were added. I had to solve this problem quickly for a demo. To solve the problem I used this notation: var predicate = PredicateExtensions.False<table2>(); if (RegNosDistinct != null) { predicate = predicate.Or(ec => RegNos.Contains(ec.regno)); } My questions are: Why does a stack overflow occur using the foreach loop? I take it Windows Server 2003 has a much smaller stack per process\thread than NT\2000\XP\Vista\Windows 7 workstation versions of Windows. Which is the fastest and most correct way to achieve this using LINQ and LINQKit? It was suggested I stop using LINQ and go back to dynamic SQL or ADO.NET but I think using LINQ and LINQKit is far better for maintainability.

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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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  • LinqKit System.InvalidCastException When Invoking method-provided expression on member property.

    - by mdworkin
    Given a simple parent/child class structure. I want to use linqkit to apply a child lambda expression on the parent. I also want the Lambda expression to be provided by a utility method. public class Foo { public Bar Bar { get; set; } } public class Bar { public string Value { get; set; } public static Expression<Func<Bar, bool>> GetLambdaX() { return c => c.Value == "A"; } } ... Expression<Func<Foo, bool>> lx = c => Bar.GetLambdaX().Invoke(c.Bar); Console.WriteLine(lx.Expand()); The above code throws System.InvalidCastException: Unable to cast object of type 'System.Linq.Expressions.MethodCallExpression' to type 'System.Linq.Expressions.LambdaExpression'. at LinqKit.ExpressionExpander.VisitMethodCall(MethodCallExpression m) at LinqKit.ExpressionVisitor.Visit(Expression exp) at LinqKit.ExpressionVisitor.VisitLambda(LambdaExpression lambda) at LinqKit.ExpressionVisitor.Visit(Expression exp) at LinqKit.Extensions.Expand<TDelegate>(Expression`1 expr) .... Please help!

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  • Howto use predicates in LINQ to Entities for Entity Framework objects

    - by user274947
    I'm using LINQ to Entities for Entity Framework objects in my Data Access Layer. My goal is to filter as much as I can from the database, without applying filtering logic on in-memory results. For that purpose Business Logic Layer passes a predicate to Data Access Layer. I mean Func<MyEntity, bool> So, if I use this predicate directly, like public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.Where(x => isMatched(x)); } I'm getting the exception [System.NotSupportedException] --- {"The LINQ expression node type 'Invoke' is not supported in LINQ to Entities."} Solution in that question suggests to use AsExpandable() method from LINQKit library. But again, using public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.AsExpandable().Where(x => isMatched(x)); } I'm getting the exception Unable to cast object of type 'System.Linq.Expressions.FieldExpression' to type 'System.Linq.Expressions.LambdaExpression' Is there way to use predicate in LINQ to Entities query for Entity Framework objects, so that it is correctly transformed it into a SQL statement. Thank you.

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  • How can I use external expressions in Linq with EF4 (and LINQKit)?

    - by neo
    I want to separate out often used expressions in linq queries. I'm using Entity Framework 4 and also LINQKit but I still don't know how I should do it the right way. Let me give you an example: Article article = dataContainer.Articles.FirstOrDefault(a => a.Id == id); IEnumerable<Comment> comments = (from c in container.Comments where CommentExpressions.IsApproved.Invoke(c) select c); public static class CommentExpressions { public static Expression<Func<Module, bool>> IsApproved { get { return m => m.IsApproved; } } } Of course the IsApproved expression would be something much more complicated. The problem is that the Invoke() won't work because I didn't call .asExpandable() from LINQKit on container.Comments but I can't call it because it's just an ICollection instead of an ObjectSet. So my question is: Do I always have to go through the data context when I want to include external expressions or can I somehow use it on the object I fetched (Article)? Any ideas or best practices? Thanks very much! neo

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  • Generated SQL with PredicateBuilder, LINQPad and operator ANY

    - by Sig. Tolleranza
    I previously asked a question about chaining conditions in Linq To Entities. Now I use LinqKit and everything works fine. I want to see the generated SQL and after reading this answer, I use LinqPad. This is my statement: var predProduct = PredicateBuilder.True<Product>(); var predColorLanguage = PredicateBuilder.True<ColorLanguage>(); predProduct = predProduct.And(p => p.IsComplete); predColorLanguage = predColorLanguage.And(c => c.IdColorEntity.Products.AsQueryable().Any(expr)); ColorLanguages.Where(predColorLanguage).Dump(); The code works in VS2008, compile and produce the correct result set, but in LinqPad, I've the following error: NotSupportedException: The overload query operator 'Any' used is not Supported. How can I see the generated SQL if LINQPad fails?

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  • C# PredicateBuilder Entities: The parameter 'f' was not bound in the specified LINQ to Entities quer

    - by Neothor
    I needed to build a dynamic filter and I wanted to keep using entities. Because of this reason I wanted to use the PredicateBuilder from albahari. I created the following code: var invoerDatums = PredicateBuilder.True<OnderzoeksVragen>(); var inner = PredicateBuilder.False<OnderzoeksVragen>(); foreach (var filter in set.RapportInvoerFilter.ToList()) { if(filter.IsDate) { var date = DateTime.Parse(filter.Waarde); invoerDatums = invoerDatums.Or(o => o.Van >= date && o.Tot <= date); } else { string temp = filter.Waarde; inner = inner.Or(o => o.OnderzoekType == temp); } } invoerDatums = invoerDatums.And(inner); var onderzoeksVragen = entities.OnderzoeksVragen .AsExpandable() .Where(invoerDatums) .ToList(); When I ran the code there was only 1 filter which wasn't a date filter. So only the inner predicate was filled. When the predicate was executed I got the following error. The parameter 'f' was not bound in the specified LINQ to Entities query expression. While searching for an answer I found the following page. But this is already implemented in the LINQKit. Does anyone else experienced this error and know how to solve it?

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  • WPF Application Slow Unresponsive when demonstrating using remote sharing software

    - by Kev
    After spending 14 hours on this I think its time to share my woes and see if anyone has experienced this issue before. Ill describe the issue and tests I have done to rule out certain things. Ok so I have a WPF application which loads in data from an SQL database. I am using DevExpress Components for datagrids, ribbons etc.. and FluentNhibernate to provide a session for database operations. I am also using log4net to log events to a textfile. Using the application on my laptop with SQL Express 2008 works fine.. the application starts up, retrieves 1000 records and I can tab through the controls on the ribbon. Now, I decided to demo the application to a third party and used remote login/sharing software online to share my desktop with the other person so as I could load the application on my laptop and they could view me using the application. Now, the application takes approx 45 seconds to load... 30 seconds with a blank database where as, when im not sharing out my screen using the online software the application loads in about 7-10 seconds. As well as that, even using the controls in the application during the demo were very sticky, slow and unresponsive. During the sharing session though however I was able to use other applications without any problems.. everything else worked fine. But I cannot understand how my application works ok under normal conditions , even browsing the net at the same time etc... BUT totally fails to perform correctly when I am sharing a session with another user... the CPU usage shot up to 100% too at times when the application was trying to start up... Please see below a list of 3rd party dlls I am using as references in my project. DevExpress dlls FluidKit PixelLab.WPF PixelLab.Common Galasoft WPF Kit FluentNHibernate NHibernate Nhibernate.ByteCode.Castle Skype4ComLib TXTEXTControl log4net LinqKit All of these DLLs are in the output folder with the application dlls created from the class assemblys in the project. So when installed via an installer on a machine the dlls will be in the same application folder as the application file itself. Many thanks

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