linq

C# Linq: Can you merge DataContexts?

Say I have one database, and this database has a set of tables that are general to all Clients and some tables that are specific to certain clients. Now what I have in mind is creating a primary DataContext that includes only the tables that are general to all the clients, and then create separate DataContexts that contain only the tabl...

Is the Linq Count() faster or slower than List.Count or Array.Length?

Is the Linq Count() method any faster or slower than List<>.Count or Array.Length? ...

Inserting a new entry to Datagrid (WPFToolkit) with Linq-Query doesn't work

I am filtering the list of entries from my DataContext with a Linq-statement. After that I assign them to the the ItemsSource-property of the DataGrid available in the WPFToolkit. The available entries are being shown, but for some reason I am not able to insert a new row into the Datagrid. Surprisingly it all works fine if do not use t...

Return single column with Linq

public string GetNameBySSN(string SSN) { var results = from c in Clients where c.ClientSSN.Equals(IRRCNumber) select c.FirstName; //return results.ToString(); } I want to return a single column value with Linq and not sure if there is way to do a quick easy return. I commented section of c...

LINQ to Objects - Does Not Contain?

I have a collection of Items that each have a collection of Relationships. I have a list of Groups that Items can have Relationships with. I can find all the Items that have a particular relationship but I now want to find all the Items that don't have a Relationship with any of my Groups. I can find the Items that have a relationship...

VerificationException Operation could destabilize the runtime on Simple LINQ Query

Here's the problem. The code below works fine on my development PC, but when I deployed the app, it crashes. Here is the lines of code that are relvant Private TdsTypesList As List(Of TDS_Type) ... TdsTypesList = (From tt In db.TDS_Types Select tt).ToList This is the error I get Exception Source: Anonymously Hosted DynamicMeth...

LINQ to SQL associations!?

Hi I have a Posts class and that post can have one file and that file can have many tags I want to iterate through the files in a post and show all the files tags foreach(File f in Post.Files) { f.Tags } What do I need in this foreach to get the top tag? there will only ever be one. i tried f.Tags.Select(n => n) with no luc...

linq: counting items in subsets of queries

I have a linq query that returs a list of int. I want to count all the items in the list. then count all the items with number 0 and then remove items with 0 from the list. please show simple example,mine is a ugly. ...

Linq: get articles with top vote count

Hi, i have a list of articles, and each article has one or more votes in a collection. It's a entity framework collection, but i don't think that makes a lot of difference for the problem. Navigating goes like this: Article.Votes, where Votes is a collection of vote objects. What i'm looking for is the Linq statement how i can find the...

Generating Linq classes from a SQL Compact 3.5 database using SQLMetal

I am generating Linq classes by running SQLMetal from the command line against a Compact 3.5 database. The Compact 3.5 database is a local database cache (generated by the Sync Framework "Create Local Database Cache wizard). CE seems to support foreign keys constraints, but I am not seeing any, and SQLMetal does not generate them into th...

Use own IComparer<T> with Linq OrderBy

I have a generic List<MyClass> where MyClass has a property "InvoiceNumber" which contains values like: 200906/1 200906/2 .. 200906/10 200906/11 200906/12 My list is bound to a BindingList<T> which supports sorting with linq: protected override void ApplySortCore( PropertyDescriptor property, ListSortDirection directi...

LINQ :: Use static DataContext to prevent Concurrency Problem

Hi i am facing some problems in my project. when i try to update entity it gives me different type of errors. i read from net. these errors are because 1 - I am getting Object of entity class from method which creates DataContext locally and in update method id does not update because here another DataContext is created locally. (eve...

LINQ to NHibernate, "get by array of ids" query

Code: public IList<T> GetByMultipleIds(int[] ids) { List<T> result = _session.Linq<T>() .Where(x => ids.Contains(x.Id)).ToList(); return result; } Throws: An exception of type 'System.NullReferenceException' occurred in NHibernate.DLL but was not handled in user code Additional inform...

How can I reuse expressions within LINQ statements?

I like to reuse expressions for DRY reasons, but how do I reuse the expressions within a LINQ statement? e.g. I have public static class MyExpressions { public static Expression<Func<Product,bool>> IsAGoodProduct() { return (p) => p.Quality>3; } } And would like to use that in LINQ statements, so var goodProds = ...

Linq with hierarchy in the data base. How do I pass on the keys?

Hi all, Here is the scene. Agents -> Organization -> Schools Agents -> Persons -> Educators So each of the 5 tables exist in the data base. The AgentId (GUID -> uniqueidentifier) is generated in the Agents table and I need it to be passed on to Organization -> Schools or Persons -> Educators. But Linq to SQL does not reconize that, an...

LINQ with generic Predicate constraint

I just upgraded my project to .NET 3.5 and thought I had a perfect use for LINQ. My application has a window manager that tracks open windows at runtime and I'm trying to add a FindOpenWindows generic method. What I've done so far: List<Form> openWindows; public List<T> FindOpenWindows<T>(Predicate<T> constraint) { ...

Return Datatype of Linq Query Result

I think I'm missing something really basic. var signatures=from person in db.People where person.Active==true select new{person.ID, person.Lname, person.Fname}; This linq query works, but I have no idea how to return the results as a public method of a class. Examples always seem to show returning the ...

How can I use LINQ to return a list of Countries but place a particular country aribitrarly at the top?

I have a table with a list of countries in it that I'm using to populate a dropdown. How can I construct a LINQ query so it will return the list of countries from that table in alphabetical order, with the exception of placing USA at the top? So, if the table contained: Sweden USA Mexico Denmark It would return: USA Denmark Mexico S...

How do you filter a collection of objects in a base class based on the type of the sub class created?

I wrote this example to help explain. As you can see I have an object hierarchy. I'd like to modify the GetFeatures() function to only return the features added by constructor of object type I instantiated. For example, BasicModel.GetFeatures(new LuxuryModel()) should only return the features "Leather Seats" and "Sunroof". I don't mind u...

LINQ Design and Prototyping

I'm about to start my first LINQ (to Entities) 'enabled' project, and it immediately strikes me how easy it is to draft SQL queries in SQL Server vs. writing and running code to check results. What do people usually do here? Prototype in T-SQL then implement in code, or use a tool, or what? ...