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Posts related to: LINQ
LINQ to SQL and missing Many to Many EntityRefs
LINQ to SQL expects every table to be mapped to have primary keys which is reasonable. However, today I ran into a problem with an existing database and a many to many relationship which did not have a Pk in the link table. The model and underlying XML seemed to map this just fine, however, the actual generated code did not approve of this arrangement.
LINQ to SQL, Lazy Loading and Prefetching
Lazy loading in an ORM can be really useful or a royal pain if you walk through a lot of data. LINQ to SQL uses lazy loading of related entities and entity sets but there are a couple of ways that allow you to do eager loading instead. Both require some extra effort and foresight.
Fun with Func<T,TResult> Delegates, Events and Async Operations
Delegates are powerful for event handling, highly useful in LINQ and a core requirement for async operations. Func<T> makes using delegate based logic a lot easier by providing a generic implemenation that in many cases allows you to skip creation of a separate delegate and instead just point at the Func<T> definition which can be a big timesaver and a nice way to remove delegate defintions from your namespaces.
System.Data.Linq.Binary is not XmlSerializable
LINQ to SQL generates TimeStamp fields as System.Data.Linq.Binary types in the data model it creates. This type unfortunately doesn't serialize and XmlSerializer and therefore Web Services in general fail with a downright serialization failure. It's possible to work around this by using internal scope but it isn't a perfect solution.
LINQ to SQL and Transactions
Using explicit Transactions with Linq to Sql is fairly rare but when you need them you'll find that it natively doesn't provide manual transaction management. Rather you have to rely on the TransactionScope class to provide transaction wrapping. Here's a contrived example, and a couple of different transaction scenarios using TransactionScope to manage multiple L2S data operation as a single transaction.
LINQ to SQL and alternate Providers
I’ve tried an interesting experiment today trying to see if I can get LINQ to SQL to run with a custom ADO.NET Data Provider I’ve created some time ago. Basically I implemented a provider that is a proxy to a remote Web  ‘service’ that can marshal SQL commands via Web Requests on a remote server. I implemented a custom provider for this interface that ships XML across the wire and marshals...
LINQ to SQL DBML fails to build or open
Arrgh. Today I got back to a LINQ to SQL app that’s been sitting idle for some time. It’s a demo app and as I started the app up and compiled the solution I got: Error 1 Build failed due to validation errors in C:\projects2008\TimeTrakker\TimeTrakkerBusiness\model\TimeTrakker.dbml. Open the file and resolve the issues in the Error List, then try rebuilding the project....
LINQPad as a Code Snippet Execution Engine
LINQPad is an awesome tool to quickly execute code. Besides the obvious LINQ testing features that its name implies, LINQPad also can come in quite handy as a generic .NET code snippet execution utility that allows you to run any .NET expression or single statement block. It's a great tool for your toolbox to quickly check behavior of BCL functions for example...
Dynamic Queries and LINQ Expressions
Using LINQ to SQL in some scenarios where dynamic expresions are required on the right side of a LINQ query expression can be tricky. How do you for example allow a query to use a dynamic field in a query and then query its data? Due to the strong typed nature of LINQ direct LINQ syntax can't be used for this sort of query, but there are a several ways to work around this by using dynamic expressions.
LINQ to SQL ObjectTrackingEnabled and Deferred Loading of Related Data
LINQ to SQL supports object tracking by default, but if running queries it's often more efficient to turn off object tracking. This can be done with ObjectTrackingEnabled, but unfortunately this option has a rather severe side effect on deferred object loading.
LINQifying - getting rid of CollectionBase?
If you're sitting on some old types that implement CollectionBase you might find that they don't directly work with LINQ. Here's how you can make these types work with LINQ.
Update to LINQ to SQL Business Object Wrapper Sample
Last night I after I posted the LINQ DataContext post I realized that I hadn't ever updated the LINQ Business Object Layer example app for .NET 3.5 RTM. Although I've long updated the code, since I use it here in a few internal applications as a base business object wrapper around LINQ to SQL, I...
Linq to SQL DataContext Lifetime Management
The DataContext is the central object that holds LINQ to SQL together. This post talks about a few different approaches you can use to hang on to your DataContext in the course of a request, to pass between layers or to manage on a per thread/request level.
LINQ To SQL and the Web.Config ConnectionString Value
I just got had by an odd behavior in the LINQ to SQL model designer when working with a LINQ to SQL Model in a separate class library project. I use LINQ to SQL in a business layer which always lives in a separate assembly and so the model does not live in the same project as the Web (or other)...
Anonymous Types in C# 3.0
One of the most convenient features of C# 3.0 is the ability to create new types 'on the fly' using Anonymous Types. Anonymous Types are essentially compiler generated types that you don't explicitly declare with an official type declaration. Rather you define the type inline as part of the code...