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• Using 'new' in a projection?

  - by davenewza

  I wish to project a collection from one type (Something) to another type (SomethingElse). Yes, this is a very open-eneded question, but which of the two options below do you prefer? Creating a new instance using new: var result = query.Select(something => new SomethingElse(something)); Using a factory: var result = query.Select(something => SomethingElse.FromSomething(something)); When I think of a projection, I generally think of it as a conversion. Using new gives me this idea that I'm creating new objects during a conversion, which doesn't feel right. Semantically, SomethingElse.FromSomething() most definitely fits better. Although, the second option does require addition code to setup a factory, which could become unnecessarily compulsive.

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• Extension methods on a null object instance – something you did not know

  - by nmarun

  Extension methods gave developers with a lot of bandwidth to do interesting (read ‘cool’) things. But there are a couple of things that we need to be aware of while using these extension methods. I have a StringUtil class that defines two extension methods: 1: public static class StringUtils 2: { 3: public static string Left( this string arg, int leftCharCount) 4: { 5: if (arg == null ) 6: { 7: throw new ArgumentNullException( "arg" ); 8: } 9: return arg.Substring(0, leftCharCount); 10...(read more)

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• Using Subjects to Deploy Queries Dynamically

  - by Roman Schindlauer

  In the previous blog posting, we showed how to construct and deploy query fragments to a StreamInsight server, and how to re-use them later. In today’s posting we’ll integrate this pattern into a method of dynamically composing a new query with an existing one. The construct that enables this scenario in StreamInsight V2.1 is a Subject. A Subject lets me create a junction element in an existing query that I can tap into while the query is running. To set this up as an end-to-end example, let’s first define a stream simulator as our data source: var generator = myApp.DefineObservable(     (TimeSpan t) => Observable.Interval(t).Select(_ => new SourcePayload())); This ‘generator’ produces a new instance of SourcePayload with a period of t (system time) as an IObservable. SourcePayload happens to have a property of type double as its payload data. Let’s also define a sink for our example—an IObserver of double values that writes to the console: var console = myApp.DefineObserver(     (string label) => Observer.Create<double>(e => Console.WriteLine("{0}: {1}", label, e)))     .Deploy("ConsoleSink"); The observer takes a string as parameter which is used as a label on the console, so that we can distinguish the output of different sink instances. Note that we also deploy this observer, so that we can retrieve it later from the server from a different process. Remember how we defined the aggregation as an IQStreamable function in the previous article? We will use that as well: var avg = myApp     .DefineStreamable((IQStreamable<SourcePayload> s, TimeSpan w) =>         from win in s.TumblingWindow(w)         select win.Avg(e => e.Value))     .Deploy("AverageQuery"); Then we define the Subject, which acts as an observable sequence as well as an observer. Thus, we can feed a single source into the Subject and have multiple consumers—that can come and go at runtime—on the other side: var subject = myApp.CreateSubject("Subject", () => new Subject<SourcePayload>()); Subject are always deployed automatically. Their name is used to retrieve them from a (potentially) different process (see below). Note that the Subject as we defined it here doesn’t know anything about temporal streams. It is merely a sequence of SourcePayloads, without any notion of StreamInsight point events or CTIs. So in order to compose a temporal query on top of the Subject, we need to 'promote' the sequence of SourcePayloads into an IQStreamable of point events, including CTIs: var stream = subject.ToPointStreamable(     e => PointEvent.CreateInsert<SourcePayload>(e.Timestamp, e),     AdvanceTimeSettings.StrictlyIncreasingStartTime); In a later posting we will show how to use Subjects that have more awareness of time and can be used as a junction between QStreamables instead of IQbservables. Having turned the Subject into a temporal stream, we can now define the aggregate on this stream. We will use the IQStreamable entity avg that we defined above: var longAverages = avg(stream, TimeSpan.FromSeconds(5)); In order to run the query, we need to bind it to a sink, and bind the subject to the source: var standardQuery = longAverages     .Bind(console("5sec average"))     .With(generator(TimeSpan.FromMilliseconds(300)).Bind(subject)); Lastly, we start the process: standardQuery.Run("StandardProcess"); Now we have a simple query running end-to-end, producing results. What follows next is the crucial part of tapping into the Subject and adding another query that runs in parallel, using the same query definition (the “AverageQuery”) but with a different window length. We are assuming that we connected to the same StreamInsight server from a different process or even client, and thus have to retrieve the previously deployed entities through their names: // simulate the addition of a 'fast' query from a separate server connection, // by retrieving the aggregation query fragment // (instead of simply using the 'avg' object) var averageQuery = myApp     .GetStreamable<IQStreamable<SourcePayload>, TimeSpan, double>("AverageQuery"); // retrieve the input sequence as a subject var inputSequence = myApp     .GetSubject<SourcePayload, SourcePayload>("Subject"); // retrieve the registered sink var sink = myApp.GetObserver<string, double>("ConsoleSink"); // turn the sequence into a temporal stream var stream2 = inputSequence.ToPointStreamable(     e => PointEvent.CreateInsert<SourcePayload>(e.Timestamp, e),     AdvanceTimeSettings.StrictlyIncreasingStartTime); // apply the query, now with a different window length var shortAverages = averageQuery(stream2, TimeSpan.FromSeconds(1)); // bind new sink to query and run it var fastQuery = shortAverages     .Bind(sink("1sec average"))     .Run("FastProcess"); The attached solution demonstrates the sample end-to-end. Regards, The StreamInsight Team

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• Passing integer lists in a sql query, best practices

  - by Artiom Chilaru

  I'm currently looking at ways to pass lists of integers in a SQL query, and try to decide which of them is best in which situation, what are the benefots of each, and what are the pitfalls, what should be avoided :) Right now I know of 3 ways that we currently use in our application. 1) Table valued parameter: Create a new Table Valued Parameter in sql server: CREATE TYPE [dbo].[TVP_INT] AS TABLE( [ID] [int] NOT NULL ) Then run the query against it: using (var conn = new SqlConnection(DataContext.GetDefaultConnectionString)) { var comm = conn.CreateCommand(); comm.CommandType = CommandType.Text; comm.CommandText = @" UPDATE DA SET [tsLastImportAttempt] = CURRENT_TIMESTAMP FROM [Account] DA JOIN @values IDs ON DA.ID = IDs.ID"; comm.Parameters.Add(new SqlParameter("values", downloadResults.Select(d => d.ID).ToDataTable()) { TypeName = "TVP_INT" }); conn.Open(); comm.ExecuteScalar(); } The major disadvantages of this method is the fact that Linq doesn't support table valued params (if you create an SP with a TVP param, linq won't be able to run it) :( 2) Convert the list to Binary and use it in Linq! This is a bit better.. Create an SP, and you can run it within linq :) To do this, the SP will have an IMAGE parameter, and we'll be using a user defined function (udf) to convert this to a table.. We currently have implementations of this function written in C++ and in assembly, both have pretty much the same performance :) Basically, each integer is represented by 4 bytes, and passed to the SP. In .NET we have an extension method that convers an IEnumerable to a byte array The extension method: public static Byte[] ToBinary(this IEnumerable intList) { return ToBinaryEnum(intList).ToArray(); } private static IEnumerable<Byte> ToBinaryEnum(IEnumerable<Int32> intList) { IEnumerator<Int32> marker = intList.GetEnumerator(); while (marker.MoveNext()) { Byte[] result = BitConverter.GetBytes(marker.Current); Array.Reverse(result); foreach (byte b in result) yield return b; } } The SP: CREATE PROCEDURE [Accounts-UpdateImportAttempts] @values IMAGE AS BEGIN UPDATE DA SET [tsLastImportAttempt] = CURRENT_TIMESTAMP FROM [Account] DA JOIN dbo.udfIntegerArray(@values, 4) IDs ON DA.ID = IDs.Value4 END And we can use it by running the SP directly, or in any linq query we need using (var db = new DataContext()) { db.Accounts_UpdateImportAttempts(downloadResults.Select(d => d.ID).ToBinary()); // or var accounts = db.Accounts .Where(a => db.udfIntegerArray(downloadResults.Select(d => d.ID).ToBinary(), 4) .Select(i => i.Value4) .Contains(a.ID)); } This method has the benefit of using compiled queries in linq (which will have the same sql definition, and query plan, so will also be cached), and can be used in SPs as well. Both these methods are theoretically unlimited, so you can pass millions of ints at a time :) 3) The simple linq .Contains() It's a more simple approach, and is perfect in simple scenarios. But is of course limited by this. using (var db = new DataContext()) { var accounts = db.Accounts .Where(a => downloadResults.Select(d => d.ID).Contains(a.ID)); } The biggest drawback of this method is that each integer in the downloadResults variable will be passed as a separate int.. In this case, the query is limited by sql (max allowed parameters in a sql query, which is a couple of thousand, if I remember right). So I'd like to ask.. What do you think is the best of these, and what other methods and approaches have I missed?

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• Dynamic Data with Subsonic 3

  - by Ezequiel Bertti

  i want to make a webproject with Subsonic and Dynamic Data... But when i go register the ContextData a don't have it in subsonic with LINQ... in Global.asax.cs a have to do something like this model.RegisterContext(SubSonicRepo, new ContextConfiguration() { ScaffoldAllTables = true }); how can i make it work? have some way to make it work? using entities or LINQ everything work... but using Subsonic with linq it not work...

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• Import Namespace System.Query

  - by GateKiller

  I am trying to load Linq on my .Net 3.5 enabled web server by adding the following to my .aspx page: <%@ Import Namespace="System.Query" %> However, this fails and tells me it cannot find the namespace. The type or namespace name 'Query' does not exist in the namespace 'System' I have also tried with no luck: System.Data.Linq System.Linq System.Xml.Linq I believe that .Net 3.5 is working because var hello = "Hello World" seems to work. Can anyone help please? Cheers, Stephen PS: I just want to clarify that I don't use Visual Studio, I simple have a Text Editor and write my code directly into .aspx files.

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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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• Mocking objects with complex Lambda Expressions as parameters

  - by iCe

  Hi there, I´m encountering this problem trying to mock some objects that receive complex lambda expressions in my projects. Mostly with with proxy objects that receive this type of delegate: Func<Tobj, Fun<TParam1, TParam2, TResult>> I have tried to use Moq as well as RhinoMocks to acomplish mocking those types of objects, however both fail. (Moq fails with NotSupportedException, and in RhinoMocks simpy does not satisgy expectation). This is simplified example of what I´m trying to do: I have a Calculator object that does calculations: public class Calculator { public Calculator() { } public int Add(int x, int y) { var result = x + y; return result; } public int Substract(int x, int y) { var result = x - y; return result; } } I need to validate parameters on every method in the Calculator class, so to keep with the Single Responsability principle, I create a validator class. I wire everything up using a Proxy class, that prevents having duplicate code: public class CalculatorProxy : CalculatorExample.ICalculatorProxy { private ILimitsValidator _validator; public CalculatorProxy(Calculator _calc, ILimitsValidator _validator) { this.Calculator = _calc; this._validator = _validator; } public int Operation(Func&lt;Calculator, Func&lt;int, int, int&gt;&gt; operation, int x, int y) { _validator.ValidateArgs(x, y); var calcMethod = operation(this.Calculator); var result = calcMethod(x, y); _validator.ValidateResult(result); return result; } public Calculator Calculator { get; private set; } } Now, I´m testing a component that does use the CalculatorProxy, so I want to mock it, for example using Rhino Mocks: [TestMethod] public void ParserWorksWithCalcultaroProxy() { var calculatorProxyMock = MockRepository.GenerateMock&lt;ICalculatorProxy&gt;(); calculatorProxyMock.Expect(x =&gt; x.Calculator).Return(_calculator); calculatorProxyMock.Expect(x =&gt; x.Operation(c =&gt; c.Add, 2, 2)).Return(4); var mathParser = new MathParser(calculatorProxyMock); mathParser.ProcessExpression("2 + 2"); calculatorProxyMock.VerifyAllExpectations(); } However I cannot get it to work! Any ideas about how this can be done? Thanks a lot!

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• Cast MyEntity To LinqEntity throw a base controller class

  - by Mohammad Kani

  hi there i design a multilayer we appliction andusing LINQ a my data provider i need to user my own Entites instead o LINQ etities. so i created Entities Project and create my entities in it. when i get data from contex and cast them to my entities , everything is ok. but when i want to cast on of my entities to linq entity , an exception thrown. in my linq entity i add CTYPE operator from and to my entities Exp : Public Class BaseController(Of LinqEntity As {BaseEntity, New}, MyEntity As ModuleEntities.BaseEntityInfo) Implements Interfaces.Base(Of ServiceEntity) 'This methd work fine and cast LinqEntity to MyEntity Public Function GetAll() As List(Of MyEntity ) Dim q = (From x In Context.GetTable(Of LinqEntity)() _ Select x).Cast(Of MyEntityBase) End Function Public Sub Update(ByVal entity As MyEntity) 'here is problem 'cast , direct cast , or anything not work Dim x as LinqEntity = entity Me.Context.GetTable(Of LinqEntity).InsertOnSubmit(entity) Me.Context.SubmiChanges() End Sub

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• extracting only elements with text (or value)

  - by guy

  hay all. i am trying to transform html to xml meaning extracting all elements with text using this code is not working maybe some one has the answer ? System.Xml.Linq.XElement query1 = new System.Xml.Linq.XElement("RawHTMLData", from q in hDoc.Descendants("TABLE") where q.HasElements select new System.Xml.Linq.XElement("TABLE" + (++i).ToString(), from j in q.Elements("TR") where j.HasElements && j.Descendants("div") != null select new System.Xml.Linq.XElement("Row", from hh in j.Descendants("div") where tt => j.Descendants("div").Contains(hh.Value) select(TT(hh)))));

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• How to reflect over T to build an expression tree for a query?

  - by Alex

  Hi all, I'm trying to build a generic class to work with entities from EF. This class talks to repositories, but it's this class that creates the expressions sent to the repositories. Anyway, I'm just trying to implement one virtual method that will act as a base for common querying. Specifically, it will accept a an int and it only needs to perform a query over the primary key of the entity in question. I've been screwing around with it and I've built a reflection which may or may not work. I say that because I get a NotSupportedException with a message of LINQ to Entities does not recognize the method 'System.Object GetValue(System.Object, System.Object[])' method, and this method cannot be translated into a store expression. So then I tried another approach and it produced the same exception but with the error of The LINQ expression node type 'ArrayIndex' is not supported in LINQ to Entities. I know it's because EF will not parse the expression the way L2S will. Anyway, I'm hopping someone with a bit more experience can point me into the right direction on this. I'm posting the entire class with both attempts I've made. public class Provider<T> where T : class { protected readonly Repository<T> Repository = null; private readonly string TEntityName = typeof(T).Name; [Inject] public Provider( Repository<T> Repository) { this.Repository = Repository; } public virtual void Add( T TEntity) { this.Repository.Insert(TEntity); } public virtual T Get( int PrimaryKey) { // The LINQ expression node type 'ArrayIndex' is not supported in // LINQ to Entities. return this.Repository.Select( t => (((int)(t as EntityObject).EntityKey.EntityKeyValues[0].Value) == PrimaryKey)).Single(); // LINQ to Entities does not recognize the method // 'System.Object GetValue(System.Object, System.Object[])' method, // and this method cannot be translated into a store expression. return this.Repository.Select( t => (((int)t.GetType().GetProperties().Single( p => (p.Name == (this.TEntityName + "Id"))).GetValue(t, null)) == PrimaryKey)).Single(); } public virtual IList<T> GetAll() { return this.Repository.Select().ToList(); } protected virtual void Save() { this.Repository.Update(); } }

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• DeleteOnSubmit doesnt exist?

  - by Anders Metnik

  using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; Thats my namespaces.. i was looking for System.Data.Linq; but it doesnt seem to be anywhere, and i guess that is what have been moved to System.Linq, since i have access to most other things in Linq. EDIT: found System.Data:Linq, no difference Here is my method: public void deleteStudienummer(int studienummer) { dbcontent = new DBEntities(); var dQry = from members in dbcontent.Medlemmer where members.Studienummer == studienummer select members; foreach (var member in dQry) { dbcontent.*** } dbcontent.AcceptAllChanges(); Console.WriteLine("delete member should have occured"); } The * was supposed to be DeleteOnSubmit, but i only have DeleteDatabase and DeleteObject, i tried with object but it doesnt work.. Have also tried dbcontent.Medlemmer.* but still not present. And AcceptAllChanges() was supposed to be .submitChanges() but that wasnt present either.

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• LINQ. Grouping by days. How to do this easily?

  - by punkouter

  I can't seem to find any god reference on this. I have alot of data in SQL with dates. So I wanted to make a line chart to show this data over time. If I want to show it over a perioud of days then I need to group by days.. But the LOGDATE is the full date.. not the DAY.. So I have this below.. but LINQ doesnt know what 'DayOfYear' property is.. HELP var q = from x in dc.ApplicationLogs let dt = x.LogDate group x by new { dayofyear = dt.Value.DayOfYear } into g select new { iCount = g.Count(), strDate = g.Key };

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• How does Concat() actually join the collections at lower level?

  - by zsharp

  What is Linq actually doing?

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• List<object>.RemoveAll - How to create an appropriate Predicate

  - by CJM

  This is a bit of noob question - I'm still fairly new to C# and generics and completely new to predicates, delegates and lamda expressions... I have a class 'Enquiries' which contains a generic list of another class called 'Vehicles'. I'm building up the code to add/edit/delete Vehicles from the parent Enquiry. And at the moment, I'm specifically looking at deletions. From what I've read so far, it appears that I can use Vehicles.RemoveAll() to delete an item with a particular VehicleID or all items with a particular EnquiryID. My problem is understanding how to feed .RemoveAll the right predicate - the examples I have seen are too simplistic (or perhaps I am too simplistic given my lack of knowledge of predicates, delegates and lambda expressions). So if I had a List<Of Vehicle> Vehicles where each Vehicle had an EnquiryID, how would I use Vehicles.RemoveAll() to remove all vehicles for a given EnquiryID? I understand there are several approaches to this so I'd be keen to hear the differences between approaches - as much as I need to get something working, this is also a learning exercise. As an supplementary question, is a Generic list the best repository for these objects? My first inclination was towards a Collection, but it appears I am out of date. Certainly Generics seem to be preferred, but I'm curious as to other alternatives. Thanks

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• How to properly translate the "var" result of a lambda expression to a concrete type?

  - by CrimsonX

  So I'm trying to learn more about lambda expressions. I read this question on stackoverflow, concurred with the chosen answer, and have attempted to implement the algorithm using a console app in C# using a simple LINQ expression. My question is: how do I translate the "var result" of the lambda expression into a usable object that I can then print the result? I would also appreciate an in-depth explanation of what is happening when I declare the outer => outer.Value.Frequency (I've read numerous explanations of lambda expressions but additional clarification would help) C# //Input : {5, 13, 6, 5, 13, 7, 8, 6, 5} //Output : {5, 5, 5, 13, 13, 6, 6, 7, 8} //The question is to arrange the numbers in the array in decreasing order of their frequency, preserving the order of their occurrence. //If there is a tie, like in this example between 13 and 6, then the number occurring first in the input array would come first in the output array. List<int> input = new List<int>(); input.Add(5); input.Add(13); input.Add(6); input.Add(5); input.Add(13); input.Add(7); input.Add(8); input.Add(6); input.Add(5); Dictionary<int, FrequencyAndValue> dictionary = new Dictionary<int, FrequencyAndValue>(); foreach (int number in input) { if (!dictionary.ContainsKey(number)) { dictionary.Add(number, new FrequencyAndValue(1, number) ); } else { dictionary[number].Frequency++; } } var result = dictionary.OrderByDescending(outer => outer.Value.Frequency); // How to translate the result into something I can print??

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• How to use Linq with Castle ActiveRecord

  - by Ronnie Overby

  I am playing around with Castle ActiveRecord and noticed that the download included the file, Castle.ActiveRecord.Linq.dll. I haven't found any documentation for using Linq with ActiveRecord, only some old blog posts. What is the usage pattern? Is Castle.ActiveRecord.Linq ready for production use? I'm using reflector, pending an answer.

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• Serializing WPF DataTemplates and {Binding Expressions} (from PowerShell?)

  - by Jaykul

  Ok, here's the deal: I have code that works in C#, but when I call it from PowerShell, it fails. I can't quite figure it out, but it's something specific to PowerShell. Here's the relevant code calling the library (assuming you've added a reference ahead of time) from C#: public class Test { [STAThread] public static void Main() { Console.WriteLine( PoshWpf.XamlHelper.RoundTripXaml( "<TextBlock Text=\"{Binding FullName}\" xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\"/>" ) ); } } Compiled into an executable, that works fine ... but if you call that method from PowerShell, it returns with no {Binding FullName} for the Text! add-type -path .\PoshWpf.dll [PoshWpf.Test]::Main() I've pasted below the entire code for the library, all wrapped up in a PowerShell Add-Type call so you can just compile it by pasting it into PowerShell (you can leave off the first and last lines if you want to paste it into a new console app in Visual Studio. To output (from PowerShell 2) as an executable, just change the -OutputType parameter to ConsoleApplication and the -OutputAssembly to PoshWpf.exe (or something). Thus, you can see that running the SAME CODE from the executable gives you the correct output. But running the two lines as above or manually calling [PoshWpf.XamlHelper]::RoundTripXaml or [PoshWpf.XamlHelper]::ConvertToXaml from PowerShell just doesn't seem to work at all ... HELP?! Add-Type -TypeDefinition @" using System; using System.ComponentModel; using System.Globalization; using System.Linq; using System.Windows; using System.Windows.Data; using System.Windows.Markup; namespace PoshWpf { public class Test { [STAThread] public static void Main() { Console.WriteLine( PoshWpf.XamlHelper.RoundTripXaml( "<TextBlock Text=\"{Binding FullName}\" xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\"/>" ) ); } } public class BindingTypeDescriptionProvider : TypeDescriptionProvider { private static readonly TypeDescriptionProvider _DEFAULT_TYPE_PROVIDER = TypeDescriptor.GetProvider(typeof(Binding)); public BindingTypeDescriptionProvider() : base(_DEFAULT_TYPE_PROVIDER) { } public override ICustomTypeDescriptor GetTypeDescriptor(Type objectType, object instance) { ICustomTypeDescriptor defaultDescriptor = base.GetTypeDescriptor(objectType, instance); return instance == null ? defaultDescriptor : new BindingCustomTypeDescriptor(defaultDescriptor); } } public class BindingCustomTypeDescriptor : CustomTypeDescriptor { public BindingCustomTypeDescriptor(ICustomTypeDescriptor parent) : base(parent) { } public override PropertyDescriptorCollection GetProperties(Attribute[] attributes) { PropertyDescriptor pd; var pdc = new PropertyDescriptorCollection(base.GetProperties(attributes).Cast<PropertyDescriptor>().ToArray()); if ((pd = pdc.Find("Source", false)) != null) { pdc.Add(TypeDescriptor.CreateProperty(typeof(Binding), pd, new Attribute[] { new DefaultValueAttribute("null") })); pdc.Remove(pd); } return pdc; } } public class BindingConverter : ExpressionConverter { public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType) { return (destinationType == typeof(MarkupExtension)) ? true : false; } public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType) { if (destinationType == typeof(MarkupExtension)) { var bindingExpression = value as BindingExpression; if (bindingExpression == null) throw new Exception(); return bindingExpression.ParentBinding; } return base.ConvertTo(context, culture, value, destinationType); } } public static class XamlHelper { static XamlHelper() { // this is absolutely vital: TypeDescriptor.AddProvider(new BindingTypeDescriptionProvider(), typeof(Binding)); TypeDescriptor.AddAttributes(typeof(BindingExpression), new Attribute[] { new TypeConverterAttribute(typeof(BindingConverter)) }); } public static string RoundTripXaml(string xaml) { return XamlWriter.Save(XamlReader.Parse(xaml)); } public static string ConvertToXaml(object wpf) { return XamlWriter.Save(wpf); } } } "@ -language CSharpVersion3 -reference PresentationCore, PresentationFramework, WindowsBase -OutputType Library -OutputAssembly PoshWpf.dll Again, you can get an executable by just altering the last line like so: "@ -language CSharpVersion3 -reference PresentationCore, PresentationFramework, WindowsBase -OutputType ConsoleApplication -OutputAssembly PoshWpf.exe

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• Does sqlite support linq-to-SQL?

  - by Greg

  Hi Does sqlite support linq-to-SQL?

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• linq to sql delete

  - by mazhar

  how would i delete in linq to sql with groupfeature object

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• Extracting the Date from a DateTime in Entity Framework 4 and LINQ

  - by Ken Cox [MVP]

  In my current ASP.NET 4 project, I’m displaying dates in a GridDateTimeColumn of Telerik’s ASP.NET Radgrid control. I don’t care about the time stuff, so my DataFormatString shows only the date bits: <telerik:GridDateTimeColumn FilterControlWidth="100px"   DataField="DateCreated" HeaderText="Created"    SortExpression="DateCreated" ReadOnly="True"    UniqueName="DateCreated" PickerType="DatePicker"    DataFormatString="{0:dd MMM yy}"> My problem was that I couldn’t get the built-in column filtering (it uses Telerik’s DatePicker control) to behave.  The DatePicker assumes that the time is 00:00:00 but the data would have times like 09:22:21. So, when you select a date and apply the EqualTo filter, you get no results. You would get results if all the time portions were 00:00:00. In essence, I wanted my Entity Framework query to give the DatePicker what it wanted… a Date without the Time portion. Fortunately, EF4 provides the TruncateTime  function. After you include Imports System.Data.Objects.EntityFunctions You’ll find that your EF queries will accept the TruncateTime function. Here’s my routine: Protected Sub RadGrid1_NeedDataSource _     (ByVal source As Object, _      ByVal e As Telerik.Web.UI.GridNeedDataSourceEventArgs) _     Handles RadGrid1.NeedDataSource     Dim ent As New OfficeBookDBEntities1     Dim TopBOMs = From t In ent.TopBom, i In ent.Items _                   Where t.BusActivityID = busActivityID _       And i.BusActivityID And t.ItemID = i.RecordID _       Order By t.DateUpdated Descending _       Select New With {.TopBomID = t.TopBomID, .ItemID = t.ItemID, _                        .PartNumber = i.PartNumber, _                        .Description = i.Description, .Notes = t.Notes, _                        .DateCreated = TruncateTime(t.DateCreated), _                        .DateUpdated = TruncateTime(t.DateUpdated)}     RadGrid1.DataSource = TopBOMs End Sub Now when I select March 14, 2011 on the DatePicker, the filter doesn’t stumble on time values that don’t make sense. Full Disclosure: Telerik gives me (and other developer MVPs) free copies of their suite.

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• Crazy Linq: performing System.ComponentModel.DataAnnotations validation in a single statement

  - by Daniel Cazzulino

  public static IEnumerable&lt;ValidationResult&gt; Validate(object component) { return from descriptor in TypeDescriptor.GetProperties(component).Cast&lt;PropertyDescriptor&gt;() from validation in descriptor.Attributes.OfType&lt;System.ComponentModel.DataAnnotations.ValidationAttribute&gt;() where !validation.IsValid(descriptor.GetValue(component)) select new ValidationResult( validation.ErrorMessage ?? string.Format(CultureInfo.CurrentUICulture, "{0} validation failed.", validation.GetType().Name), new[] { descriptor.Name }); } ...Read full article

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• Linq To Dataset: Display the contents of several tables in a data control

  In several cases we will be required to work with data in different datasets, or on the same dataset but at different DataTables

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• Fixing LINQ Error: Sequence contains no elements

  - by ChrisD

  I’ve read some posts regarding this error when using the First() or Single() command.   They suggest using FirstOrDefault() or SingleorDefault() instead. But I recently encountered it when using a Sum() command in conjunction with a Where():   Code Snippet var effectiveFloor = policies.Where(p => p.PricingStrategy == PricingStrategy.EstablishFloor).Max(p => p.Amount);   When the Where() function eliminated all the items in the policies collection, the Sum() command threw the “Sequence contains no elements” exception.   Inserting the DefaultIfEmpty() command between the Where() and Sum(), prevents this error: Code Snippet var effectiveFloor = policies.Where(p => p.PricingStrategy == PricingStrategy.EstablishFloor).DefaultIfEmpty().Max(p => p.Amount);   but now throws a Null Reference exception!   The Fix: Using a combination of DefaultIfEmpty() and a null check in the Sum() command solves this problem entirely: Code Snippet var effectiveFloor = policies.Where(p => p.PricingStrategy == PricingStrategy.EstablishFloor).DefaultIfEmpty().Max(p =>  p==null?0 :p.Amount);

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• How to profile LINQ to Entities queries in your asp.net applications - part 3

  - by nikolaosk

  In this post I will continue exploring ways on how to profile database activity when using the Entity Framework as the data access layer in our applications. If you want to read the first post of the series click here . If you want to read the second post of the series click here . In this post I will use the excellent (best tool for EF profiling) which is called Entity Framework Profiler. You can download the trial - fully functional edition of this tool from here . I will use the previous example...(read more)

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