linq

Linq - Casting IQueryable to IList returns null - WHY?

I have to be missing something obvious here. I don't get why this cast of the results of a linq query returns null and not the typed list I'm requesting. IList<IMyDataInterface> list = query.ToList() as IList<IMyDataInterface>; The complete code to run this is below. This is a knowledge gap I need to bridge. I have tried all kinds of ...

How do I use ."Include" on a Service Operation for ADO.Net Data Services

I am using ADO.Net Data Services and have a Service Operation that ends up returning the results of some linq to entities statements. As a part of those Linq statements there is a .Include("NavProp") to include a sub-object. When running this service operation it doesn't appear to return that expanded Include. Does anyone know either ...

Inheriting a Linq to SQL class and cast the result of a linq query

I am writing an application where we will need to extend a basic entity into a number of different things (eg employee, vehicle etc). The design is as such that there is a Entity table and a second table with type specific values eg an employee will have an ID Number but a vehicle will have a registration number. I have inherited from ...

Reasons to Learn LINQ

I don't know LINQ, but from reading a lot around this site and others, it's a MUST HAVE skill for C# developers. The problem is I am so booked on projects at work I have no time to pick up LINQ, I need to convince my boss to let me (and fellow coders) set aside some time so that we can become a LINQ house. So.. my question is, what ar...

LINQ to DATASET update with a stored procedure

I have used LINQ to SQL with a update stored procedure to update databases in the past. I wanted to know if there is anything similar in LINQ to Dataset An example of the LINQ to SQL Update: Dim lqUpdate = lqUpdate.sprocUpdate(ColumnName, NewValue, ID) ...

LINQBridge users: is it feature-complete?

For desktop programmers, do you avoid deploying .NET 3.5 framework on client machines for its big footprint? If so, is LINQBridge feature-complete? [EDIT] .NET 3.5 Framework evokes a feeling of OLE 2.0 (aka COM). When 2.0 newly came out, some users then are asking if there will be OLE version 3.0. But there will be none. OLE 2.0 is...

Building Dynamic LINQ Queries based on Combobox Value

I have a combo box in Silverlight. It has a collection of values built out of the properties of one of my LINQ-to-SQL objects (ie Name, Address, Age, etc...). I would like to filter my results based off the value selected in a combo box. Example: Say I want everyone with a last name "Smith". I'd select 'Last Name' from the drop down ...

Best resource for learning LAMBDA expressions

What are the best resources to learn LAMBDA expressions? They still have me a bit confused and I don't use them much. Also LINQ has me a bit confused, since both things are more or less in the same boat, maybe you guys can offer some good LINQ resources too. ...

complex query using LINQ and C#

hello I have a very big problem solving this issue I have 2 tables first table is : which contains a modules (id and name) second table is which contains users ids and their preferred modules' numbers now lets move to the problem I want to generate a list of checkboxes for example for the userid 1 which has the following module...

How can I write my own LINQ provider to query some custom store?

I am planning to write a LINQ provider, so that I can query data in a custom store - for example, let us say, some custom file format. What is a good way to start? Any examples? ...

What's wrong with this linq expression?

List<PageInfo> subPages = new List<PageInfo>(); // ... // some code to populate subPages here... // ... List<Guid> subPageGuids = new List<Guid> {from x in subPages select x.Id}; //doesn't work PageInfo has an Id field which is of type Guid. So x.Id is a System.Guid. 2nd line of code above does not work...I get two errors: The best ...

LINQ - Is it possible with dynamic LINQ to dynamically specify the from clause?

Hi I want to build dynamic linq. But I want to dynamically set the table (from clause) Is this possible? Malcolm ...

LINQ to SQL - Update to increment a non-primary-key field - thread-safe

I have two tables (well, two relevant for this question) : Bets (holds the bets; Columns : Id, , MessagesPosted, ) Bets_Messages (holds the bets' forum messages; Columns : Id, BetId, ) When I insert a new BetMessage in Bets_Messages I want to update (increment to be precise) the corresponding field in Bets. In pure T-SQL that would be...

How to delay loading aproperty with linq to sql external mapping?

I have a table that contains some blob fields that I don't want to load by default. In a dbml file it is possible to set the delay loaded property for such fields. Is there a similar option for external mapping files? ...

Using Linq to get a single column rowset from a stored procedure, How can I clean up this hack job?

I've got a guy who is a wizard at writing stored procs and he can munch 10 tables down to a single column in no time at all. I'm half tempted to invest a couple of days to work with him on returning XML instead of rowsets because I can digest those all day long without any problem. I say that because it is a challenge to get a result of ...

LINQ InsertOnSubmit: NullReferenceException

I have this code: using DC = MV6DataContext; using MV6; // Business Logic Layer // ... public DC.MV6DataContext dc = new DC.MV6DataContext(ConnectionString); IP ip = new IP(Request.UserHostAddress); dc.IPs.InsertOnSubmit(ip); dc.SubmitChanges(); // in Business Logic layer: public class IP : DC.IP { public IP(string address) { ... } ...

Linq SubmitChanges does not work

Hi, I have some code like this: Function GetTypeFromTableName(ByVal _TableName As String, ByVal _DataContext As DataContext) Dim Mytype As Type = (From t In _DataContext.Mapping.GetTables Where t.TableName = "dbo." + _TableName Select t.RowType.Type).SingleOrDefault Return Mytype End Function Dim DBA As ...

C# LINQ Query - Group By

Hi, I'm having a hard time understanding how I can form a LINQ query to do the following: I have a table CallLogs and I want to get back a single result which represents the call that has the longest duration. The row looks like this: [ID] [RemoteParty] [Duration] There can be multiple rows for the same RemoteParty, each which repre...

Linq to Sql Enums and Conditional Operator

Whichever way I do it, it seems something goes wrong when using the conditional operator on enum values in Linq to Sql. For example var ret = from listings in db.Listings select new Listing { ID = listings.ID, //etc OrderStatus = listings.OrderItems.Count > 0 ? listings.OrderItems.First().Order.OrderStatus : OrderStatu...

multiple orderby in this linq code

How do I add a second item to order by with this? I want to order by a goalsScored element too. var theteams = (from teams in xdoc.Descendants("team") orderby (int)teams.Element("points") descending select new Team(teams.Element("teamID").Value, (int)teams.Elem...