linq

Linq to XML, select all attributes and their values for a given node

I have an xml mapping file that looks something like this <colourMappings> <model name="modelX"> <mapping colour="White" configCode="1"></mapping> <mapping colour="Aluminium" configCode="2"></mapping> <mapping colour="Black" configCode="3"></mapping> <mapping colour="Blue" configCode="4"></mapping> ...

Why is List<>.OrderBy LINQ faster than IComparable+List<>.Sort in Debug mode?

I was interested in whether it would be faster to sort my classes using LINQ, or by implementing the IComparable interface and List.Sort. I was quite surprised when the LINQ code was faster. To do the test, I made a very simple class with the not-so-apt name of TestSort, implementing IComparable. class TestSort: IComparable<TestSort> ...

Do you choose Linq over Forloops?

Given a datatable containing two columns like this: Private Function CreateDataTable() As DataTable Dim customerTable As New DataTable("Customers") customerTable.Columns.Add(New DataColumn("Id", GetType(System.Int32))) customerTable.Columns.Add(New DataColumn("Name", GetType(System.String))) Dim row1 = customerTable.New...

LINQ Grouping: Select row instead of key?

I probably won't be able to explain this well enough, but here it goes... I have a table similar to this: Id | Foreign_Key_Id | A_Number | Some_Other_Info 1 1 100 Red 2 1 200 Blue 3 1 300 Orange 4 2 100 Green 5 2 ...

Linq vs MS Enterprise Library DAAB

At work, we just upgraded from VS2005 to 2010. To this point, we've only used sprocs (I guess out of habit more than anything). I've been playing around with Linq (very simple tutorials - nothing major). As my first actual experience with an ORM, I like it. In addition, I've only recently become familiar with the Enterprise Library bloc...

Late binding operations cannot be converted to an expression tree with LINQ

I currently have a View in MVC where I pass a single set of data to the view. However, I've come across a problem where I am having to use a LINQ query within a For Each loop in the View to pull out additional information from a SQL View of data from another DB. The error I'm getting is Late binding operations cannot be converted to an ...

Is there a better way to aggregate a dictionary using LINQ?

I am trying to build a dictionary from an enumerable, but I need an aggregator for all potentially duplicate keys. Using ToDictionary() directly was occasionally causing duplicate keys. In this case, I have a bunch of time entries ({ DateTime Date, double Hours }), and if multiple time entries occur on the same day, I want the total ti...

Cache delegate of compiled Dynamic Linq Func<> *without* params?

I'm using the Dynamic.ParseLambda method from the Dynamic LINQ library to create expressions, compile each to a Func<>, and cache each in a dictionary: // parse some dynamic expression using this ParseLambda sig: Expression<Func<TArgument,TResult>> funcExpr = System.Linq.Dynamic.ParseLambda<TArgument, TResult>( expressionString, // ...

Linq - InvalidCastException - Why does "where" not filter the invalid types

Had a problem in a complex linq query so I simplified it in LINQPad: void Main() { List<basetype> items = new List<basetype>() { new typeA() { baseproperty = "1", extendedproperty = 1 }, new typeB() { baseproperty = "2", extendedproperty = 1.1 }, new typeA() { baseproperty = "3", extendedproperty = 1 }, ...

Linq Orderby random

i'm using Asp.net MVC with Sharp Architecture. I have this code: return _repositoryKeyWord.FindAll(x => x.Category.Id == idCAtegory) .Take(50).ToList(); How can i order by random? Note: i don't want to order the 50 extracted items, i want order before and then extract 50 items. thks ...

Is there a library to use Linq to directly query databases, dynamically?

I have a very dynamic SQL Server problem to solve. I am developing a tool that verifies matched data in multiple databases. [NOTE: the requirements on this project are pretty strict] I need to make a C# tool that lets a user select any database from a dynamic list, then lets the user select a table (acting as a source db/table). Once th...

Including the EntityObject in a LINQ To Entities Projection Without Including All Columns

I have an entity with three columns, a, b, and c. If I project the ObjectSet to objects of an anonymous class: var ret = e.foos.Select(x => new { a = x.a, b = x.b }).ToList(); Then the actual SQL only includes the columns necessary to populate each object: SELECT [Extent1].[a] AS [a], [Extent1].[b] AS [b] FROM [dbo].[foo] ...

Image retrieval optimisation with LINQ

Hi, I'm working on optimising the image retrieval from the database with LINQ. The approximate image size is 4000 * 1000 pixels which weighs about 400-600KBs. The images are retrieved through a controller which is being called by a webservice. Web service gets called through jQuery. The first image that gets retrieved in about 0.7 - ...

Why linq LinqServerModeData not working?

I work on Northwind database <dxwgv:ASPxGridView ID="ASPxGridView1" runat="server" AutoGenerateColumns="False" DataSourceID="LinqServerModeDataSource1" KeyFieldName="CategoryID"> <Columns> <dxwgv:GridViewCommandColumn VisibleIndex="0"> <EditButton Visible="True...

Can this Linq query be typed as anything other than "var"?

When I do a query that returns an anonymous type var assets = from Product p in Session.CreateLinq<Product>() where bundles.Contains(p.ProductBundle) select new {p.Asset, p.Asset.PropertyTbl}; Can I type the return to anything other than var? ...

In linq how to work on Storprocedure

I work on Northwind database.server MS2008.In linq i active a sp then show me the bellow error: Syntax : <dxwgv:ASPxGridView ID="ASPxGridView1" runat="server" AutoGenerateColumns="False" DataSourceID="LinqServerModeDataSource1" KeyFieldName="CategoryID"> <Columns> <dxwgv:GridViewCom...

Is it still benefitial to think about NHibernate for .Net while there is LINQ to SQL possibility?

Hi, I am not very familiar with both LINQ to SQL and NHibernate. As far as I understand LINQ to SQL is a kind of replacement of NHIbernate for .Net in many ways. So does this mean that LINQ to SQL is a built-in replacament of NHibernate which let's a .Net developer to skip NHibernate and start to work with LINQ to SQL? Thanks ...

What is LINQ exactly ?

Possible Duplicate: Learning about LINQ Hi everyone, I just want to understand what exactly is LINQ in DOTNET? And How does it work? Tx ...

LINQ query - Multiple where with multiple sub queries based on int array

I have a sql query that performs the type of select I'm after: select * from Products p where p.ProductId in ( select distinct ProductId from ProductFacets where ProductId in (select ProductId from ProductFacets where FacetTypeId = 1) and ProductId in (select ProductId from ProductFacets where FacetTypeId = 4) ) There can...

Problem displaying a linq query in a datagridview

Hello: I am working on a C# project that reads an XML file and returns a list of lists. When I want to display a list I do this: IEnumerable<Foo> myFooQuery = from t in myLists.SelectMany( l => l.bar) orderby t.StartTime descending select t; dataGridView1.DataSource = myFooQuer...