linq

Linq Expression in nHibernate...

I have an interface, called IRepository. One of the methods in this interface is: IEnumerable<T> FindByQuery(Expression<Func<T, bool>> predicate); I then have (for example) an IUserRepository, that implements IRepository. In my implementation of IUserRepository, currently called LinqToSqlUserRepository, i have implemented the FindByQ...

DeSerialize DataTable Row Collection into List<T>

I have a DataTable with rows of data. I have a class with properties that match the row column names. How can I have a List that is populated from the DataTable Row information? Do I call something like (MyType)new XmlSerializer(typeof(MyType)).Deserialize(new XMLReader(Table.WriteXML())); ...

How can you coalesce a datetimeoffset in Linq to SQL?

I have a Linq query that orders by a datetimeoffest. The goal is to have the one that is NULL at the top, followed by most recent, 2nd recent, and so on. I started with this. orderby item.Date descending Doing it this way the NULLs go to the bottom. So I changed it to this. orderby (item.Date.HasValue ? item.Date.Value.Ticks : long.M...

LINQ: multiple Where calls only uses last one???

I'm trying to get a query going that will search multiple tags. The tags are db based and I've related them to the entity with a junction table. If I search with 1 tag, I get the correct results, but if I search with 2 tags, I only get the entities that match the second tag. Here's the C# code that builds the IQueryable: var awTable ...

Can multiple compiled linq queries be chained together?

I am trying to chain multiple compiled linq queries together. I have succeeded in chaining two queries together, but I cannot get a chain of three to work correctly. So here is a reduction of my code to recreate the issue. My two questions are: 'Why isn't this working?' and 'Is there a better way to keep the performance benefit of com...

Returning a single value with Linq to SQL

I'm learning Linq to SQL and I'm having trouble grasping it. I'm trying to simply return a single (boolean) value in C# with a Linq query. I want to see if the owner of a story would like an email notification sent when new comments are added. I would like the method that contains the Linq to SQL to return a boolean value. public bo...

using Linq to generate a collection of things to be removed from another collection

I'm familiar with the problem of modifying a collection while looping over it with a foreach loop (i.e. "System.InvalidOperationException: Collection was modified"). However, it doesn't make sense to me that when I use Linq to create a List of keys to delete from a dictionary, then loop over my new List, I get the same exception. Code ...

Iterate through data returned from var to get names and values of columns

I am using Linq to Entities in a method and returning specific columns of data from the method. I don't know what type I'll be returning so I rigged it to return a List. If someone knows a better way than the way I rigged it, PLEASE let me know. See the code below. After returning this data, I then need to iterate through the colum...

How to insert an empty row in a combobox filled by linq?

I have a list of Items, given by Linq from the DB. Now I filled a ComboBox with this list. How I can get an empty row in it? My problem is that in the list the values aren't allowed to be null, so I can't easily add a new empty item. ...

Linq update problem

Hello I have an application with user and admin sections. If an admin updates data with the help of sql datasource then it's updated the database. However, when we retrieve data with linq query then it's showing its old value rather than the updated value. After some time, the linq query automatically shows the correct value. I think ...

A cumbersome linq query

I have the following setup: Tasks, Accounts and Groups tables. Tasks can be assigned to both individual accounts and groups. I've made two supporting tables: TasksAndAccounts and AccountsInGroups. TasksAndAccounts table has the following fields: TaskId, AccountId, GroupId and AccountsInGroups has AccountId and GroupId fields. I'm trying ...

LINQ vs SQL while working with RDBMS

Can I absolutely abandon SQL if I choose LINQ? If Yes, then, Should I absolutely abandon SQL if I choose LINQ? After making a connection to RDBMS using DataContext-class, do I actually need SQL? ...

Cast from filtered custom List<T> with LINQ

I have a custom list which inherits from Generic.List<T> like this: public class TransferFileList<T> : List<TransferFile> { .. } When I set (where 'Files' is a TransferFileList<T>): var files = uploadResponse.Files.Where(x => !x.Success).ToList() the 'files' object resolves as System.Collections.Generic.List<TransferFile>, not Tran...

NHibernate: HasMany components and Where/Contains clause

Hi, I'm trying to work out how to create a query using Linq to NHibernate. I have two classes like this: public class Foo { private ISet<Bar> _bars = new HashedSet<Bar>(); public virtual ISet<Bar> Bars { get { return _bars; } set { _bars = value; } } } public class Bar { public string Name { get; se...

Iterating Linq result set using indexers

Let's ay I have this query: var results = from row in db.Table select row; How can I access this: string name = results[0]["columnName"]; ...

LINQ to SQL Cannot create database [Schema Permissions]

For some integration tests I want to use LINQ to SQL to drop/re-create the test database. I've had this working fine before, however in this project the database is split up into several schemas. When I try to run the ctx.CreateDatabase() command I'm getting this exception: The specified schema name "xyz" either does not exist or...

Composing Linq to Entity Query from multiple parameters

I'm currently building a detailed search and I am trying to figure out how to compose my Linq query to my Entity. basically I have users that can select 1* items in a list control. the part I can't wrap my head around is the following: how can I dynamically build a Where AND( field is equal to this OR field is equal to this OR...) cla...

Linq: Sum of int

I am getting "The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type" When executing Sum() of my empty statement. ResultView works fine, but either var r = from v in DataContext.Visits join bs in DataContext.BaseContents on v.BaseContentID equals bs.Id where (bs.CreatedBy ...

Linq query help

I'm attempting to write a linq query which uses several tables of related data and have gotten stuck. The expected result: I need to return the three most populous metropolitan areas per region by population descending. tables w/sample data: MetroAreas -- ID, Name 2, Greater New York Cities -- ID, Name, StateID 1293912, New York City...

foreach in linq result not working

Don't know what's wrong here, when I run the application it says "Specified method is not supported" pointing at "var result in query" in foreach loop. Please help... var query = from c in entities.Customer select c.CustomerName; List<string> customerNames = new List<string>(); foreach (var result in query) { customerN...