linq

"Only one expression can be specified in the select list when the subquery is not introduced with EXISTS."

I have a fairly complex Linq query: var q = from eiods in LinqUtils.GetTable<EIOfficialDesignee>() let eiodent = eiods.Entity join tel in LinqUtils.GetTable<EntityTelephone>() on new { EntityID = eiodent.ID, TelephoneType = EntityTelephone.TTelephone.Office } equals new { tel.EntityID, tel.TelephoneType } ...

.NET: LINQ's Last()

I'm new to LINQ and LINQ to SQL and don't understand what's wrong with this code. The Excetpion.Message I get is "Query operator 'Last' is not supported." What I'm trying to do is get the earliest LastActivityUtc out of the latest 100. The code follows. var postTimes = from post in db.Post where p...

Help me make this LINQ query faster please?

To Set up the scenario, Lets say I have 100000 rows in the table and it grows more and more each day. This queue currently takes over 2 seconds to retrieve only about 40 or 50 rows from the table. The data in this table are grouped by DateTime references so I start off grouping all the data by DateTime because this is the only equal va...

dynamic join in linq 0 c#

var query = from C in db.clients join O in db.orders on c.clientid equals O.clientid join P in db.products on O.productid equals P.productid select new {C,O}; I want to perform a search based on the above join. The input param could be C.ClientID and/or P.ProductName and/or P.ProductType and/or O.ShippingType How woul...

Linq "Could not translate expression... into SQL and could not treat it as a local expression."

I started out with this question, which I sort of answered there, and now I'm asking the more fundamental question here. I've simplified the query down to this: var q = from ent in LinqUtils.GetTable<Entity>() from tel in ent.Telephones.DefaultIfEmpty() select new { Name = ent.FormattedName, Tel = te...

Patterns/Practices for encapsulating predicates

I'm guessing most of us have to deal with this at some point so I thought I'd ask the question. When you have a lot of collections in your BLL and you find that you're writing the same old inline (anonymous) predicates over and over then there's clearly a case for encapsulation there but what's the best way to achieve that? The project...

Stored Proc in RIA Services

Hi I want to load some data with a SP. I've put a SP in a Linq to SQL Class and I don't know how to use it for loading it's data in a datagrid. In LinqToSqlDomainService I can't figure out how to call a SP. What steps should I use. Any samples of this ? All samples use a table. Thank's ...

Simple, linq-able, file based database

Hey, what's the easiest way to use a file-based database with LINQ in C#? It would be best if I could use it without installing extra components. EDIT: I want to use it for a file index. Not the whole file system, but the database should be not too slow and not too big. ...

Retrieving an image from database with Linq to SQL

In my database I have stored images in the "image" data type, showing up as a binary code. I now want to retrieve all images from one column and diplay them on a asp.net page with C#. databaseDataContext db = new databaseDataContext(); var images = from Picture p in db.Pictures select p.pictureThumb; then I use t...

Many-to-Many implementation in linq-to-sql

Does anybody know an example of correct many-to-many implementation in Linq-to-Sql? Usually i use intermediate entity (e.g. CustomerProducts) in DataContext, and join it at every query. The idea is to hide intermediate entity from object level by adding custom properties to partial classes - use collections like IEnumerabe Customer.Prod...

bool column in where clause - linq/c#

Expression<Func<Employee, bool>> employeeWhere = R => true; employeeWhere = R => R.PositionCode == "M"; employeeWhere = R => R.IsActive; //want only ones which are true Will the above build me a query of this : SELECT * FROM EMPLOYEE WHERE POSITIONCODE = "M" && IsActive = 1 This is what I want to return var result = _db.Employ...

Append to an expression - linq/c#

Based on my question from yesterday: link text if I had to append to my existing 'where' expression, how would i append? Expression<Func<Client, bool>> clientWhere = c => true; if (filterByClientFName) { clientWhere = c => c.ClientFName == searchForClientFName; } if (filterByClientLName) { clientWhere = c => c.Clie...

How to find the maximum value for each key in a List of Dictionaries using LINQ?

I have a List of Dictionaries that have keys of type string and values that are ints. Many of the dictionaries have the same keys in them but not all of them. So my question is: using LINQ how would I find the maximum value associated with each distinct key across all of the dictionaries? So for example given the following input: var...

Linq Efficiency question - foreach vs aggregates

Which is more efficient? //Option 1 foreach (var q in baseQuery) { m_TotalCashDeposit += q.deposit.Cash m_TotalCheckDeposit += q.deposit.Check m_TotalCashWithdrawal += q.withdraw.Cash m_TotalCheckWithdrawal += q.withdraw.Check } //Option 2 m_TotalCashDeposit = baseQuery.Sum(q => q.deposit.Cash); m_TotalCheckDeposit = baseQuery....

Group By Dates using Linq

What I have is a set of users with join dates and I want to use GoogleChartSharp to create a chart showing how many users have joined each month. So I have this set of dates (US format) in a list: 01/01/2009 02/01/2009 02/12/2009 03/02/2009 03/12/2009 03/22/2009 Googlechartsharp requires me to do someth...

can't select into class using linq

I have a query that works fine when using an anonymous type but as soon as I try to un-anonymize it it fails to select all values into the class. here is the linq i'm using (in combination with Subsonic 3): var producten = (from p in Premy.All() join pr in Producten.All() on p.dekking equals pr.ID where p.kilometragemax >= 10...

How to update with Linq-To-SQL?

I need to update values but I am looping all the tables values to do it: public static void Update(IEnumerable<Sample> samples , DataClassesDataContext db) { foreach (var sample in db.Samples) { var matches = samples.Where(a => a.Id == sample.Id); if(matches.Any()) { var match = matches.Fi...

Select Rows from a DataSet using LINQ, where the list of RowsID's are in a List<T>

First I have to say, that I am a newby using LINQ. Actually I never used before, but I am having a task where I need to filter a DataTable, using values that will come from a List. So I will like to know if it's possible in LINQ to query on a Datatable using values in the List as Filter values. Some one can give me some hint's Thank you...

HQL vs Linq to objects

I need to get the products in the system that match certain criteria. How should i decide if I should write an HQL and get all products that match the criteria from DB or write a Linq query directly to the main List that contain all products in the system. Which should be better performance vise ...

How do I do this in Entity Framework(multiple where's or Join)?

Hi I have 2 tables that have a relation ship to each other Table A has 1 to many relationship with table B so this make a navigation property into each. Now I need to check a value from Table A(userName) and I need to check a value from table B(ClubId). So in my mind it would be something like Join the tables together Where A.userN...