linq

C# functional quicksort is failing

I'm trying to implement quicksort in a functional style using C# using linq, and this code randomly works/doesn't work, and I can't figure out why. Important to mention: When I call this on an array or list, it works fine. But on an unknown-what-it-really-is IEnumerable, it goes insane (loses values or crashes, usually. sometimes works.)...

Overriding LINQ extension methods

Is there a way to override extension methods (provide a better implementation), without explicitly having to cast to them? I'm implementing a data type that is able to handle certain operations more efficiently than the default extension methods, but I'd like to keep the generality of IEnumerable. That way any IEnumerable can be passed, ...

'Recursive' LINQ calls

Hi, I'm trying to build an XML tree of some data with a parent child relationship, but in the same table. The two fields of importance are CompetitionID ParentCompetitionID Some data might be CompetitionID=1, ParentCompetitionID=null CompetitionID=2, ParentCompetitionID=1 CompetitionID=3, ParentCompetitionID=1 The broken query I ...

Linq to Entities custom ordering via position mapping table

Hi, I have a news table and I would like to implement custom ordering. I have done this before via a positional mapping table which has newsIds and a position. I then LEFT OUTER JOIN the position table ON news.newsId = position.itemId with a select case statement CASE WHEN [position] IS NULL THEN 9999 ELSE [position] END and order ...

Mysql and Subsonic 3 with LINQ: Cannot insert rows

I'm using Susbsonic 3 with the LINQ templates. I've already added a column called 'ID' to my Articles table. When I try to insert a row using the following code var db = new LDB(); int newID = db.Insert.Into<ArticlesTable> ( x => x.Description ).V...

C# asp.net MVC: When to update LastActivityDate?

I'm using asp.net mvc and creating a public website. I need to keep track of users that are online. I see that the standard way in asp.net of doing this is to keep track of LastActivityDate. My question is when should I update this? If I update it every time the users clicks somewhere, I will feel a performance draw back. However if I d...

'And' operator in Linq

I have a query that prints userid in label1 when username is entered.Works fine; but i want to write query for username and password that prints userid. so how can i write it? i tried writing using 'and' operator but dont seems to work. int id = (from auser in lq.logins where auser.username == userNameString //&& auser.Passwo...

IEnumerable and iqueryable

Possible Duplicate: What is the difference between IQueryable<T> and IEnumerable<T>? What is IQueryable and ienumberable ...

filtering problem in LINQ

var query = from d in testPersons.person where d.Name == txtbox select d; txtbox is text box on View page. How change this code to return all names who starts with any part of name? For example: When I type R in text box, on View page, this query should return all names who is start with character R ...

Dynamic group by in linq to objects on Silverlight

How can i do dynamic group by in linq to objects in #siverlight client side? i want to do something like this: var x = "empt.Dept"; var groups = from emp in employees group emp by x into g select new { Dept = g.Key, Count = g.Count() }; I tryed also to use reflection and do something like employee.GetType().GetProperty("Dep...

Update 2 table values in one query in LINQ

Hello, I have 2 tables Table1 with columns [BId,Name,Amount] Table2 with columns [CId,BId, ExpenseType,Expense]. BId Is the foreign key in Table2. The Amount field in Table1 is always higher than Expense in Table2. I need to update the values of Amount (increase or decrease) based on value of Expense and I want to do it in single quer...

How can I use Linq to create an array of dictionaries from XML?

Given the following XML structure: <courses> <course> <title>foo</title> <description>bar</description> </course> ... </courses> How could I create an array of dictionaries such that each dictionary contains all the element/value pairs within a course? What I have right now generates an array whose elements contain a si...

Weighted Average with LINQ

My goal is to get a weighted average from one table, based on another tables primary key. Example Data: Table1 Key WEIGHTED_AVERAGE 0200 0 Table2 ForeignKey LENGTH PCR 0200 105 52 0200 105 60 0200 105 54 0200 105 -1 0200 47 55 I need to get ...

not strongly typed view problem

Controller action: public ActionResult Index() { probaEntities proba = new probaEntities(); probaEntities proba1 = new probaEntities(); probaEntities proba2 = new probaEntities(); var query = from i in proba.name from j in proba1.id_person from k in proba2.last_n...

Convert Python 3.x snippet to C#/LINQ.

I want to sort elements of a HashSet<string> and join them by a ; character. Python interpreter version: >>> st = {'jhg', 'uywer', 'nbcm', 'utr'} >>> strng = ';'.join(sorted(s)) >>> strng 'ASD;anmbh;ashgg;jhghjg' C# signature of a method I seek: private string getVersionsSorted(HashSet<string> versions); I can do this without usin...

Problem with LINQ Generated class and IEnumerable to Excel

Hi all, I wrote a method which exports values to excel file from an IEnumerable parameter. Method worked fine for my little test class and i was happy till i test my method with a LINQ class. Method: public static void IEnumerableToExcel<T>(IEnumerable<T> data, HttpResponse Response) { Response.Clear(); Response.Co...

Select a Column Dynamically using LINQ?

Hi all I am trying to do a very simple dynamic query which will select a column dynamically I mean the selection of column would depend upon another query so I would select x col if cond1 and y if cond2 so I tried using query.Select(colname) using the extension method also tried using Func<> but I am not sure how to go about this I have ...

Delete query in Linq

I have this simple code but it shows error. I dont know where I am going wrong. I shows error in last line.."DeleteOnSubmit" linq_testDataContext db = new linq_testDataContext(); var remove = from aremove in db.logins where aremove.username == userNameString && aremove.Password == pwdString select aremove; db.logins.D...

How to use Linq in Mono?

I can't make System.Linq (aka. Linq-to-objects) work. I am running MonoDevelop 2.2.1 in Ubuntu 10 Lucid Lynx with Mono 2.4.4. They advertise in their site that they implemented Linq, but I can't even find Enumerable.Range or .ToArray(). What's wrong? ...

Linq guru - filtering related entities...

My table structure is as follows: Person 1-M PesonAddress Person 1-M PesonPhone Person 1-M PesonEmail Person 1-M Contract Contract M-M Program Contract M-1 Organization At the end of this query I need a populated object graph where each person has their: PesonAddress's PesonPhone's PesonEmail's PesonPhone's Contract's - and this h...