Sql – Linq to SQL & Logical partitioning (DAL, BLL)

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We're going to be rebuilding one of our sites in .Net. I've read many articles and really like the idea of separating our project into a data access layer (DAL), Business logic layer (BLL), and presentation layer (we're coming from classic ASP so this is a massive step for us). I also really like Linq to SQL.

Since Linq to SQL is aimed at rapid development, is it really possible with Linq to SQL to have a DAL, BLL, and presentation layer? With Linq to SQL would the DAL return the entities or the linq code which could be possibly modified in the BLL? The relationship between the DAL and BLL with Linq to SQL seems to be a fuzzy topic with no consensus – and since this is such a big jump for us I definitely want to have a good game plan before diving into anything.

Typed Datasets seem more equipped for this, but if I can get something similar with Linq I'd go that route.

I'd like to stay away from nHibernate and other 3rd party libraries.

Best Answer

We're building exactly what you described, and we're using L2S to do it. Agreed that the relationship between the DAL and BLL is a bit fuzzy, but we have a distinct BLL and a distinct DAL. All our logic is in the BLL and all data retrieval/modification is done via calls to the DAL (using LINQ calls).

Our app uses no typed datasets. We've built entity classes to represent our objects. Now that I've spent a couple months building part of this, I don't see us (me) ever going back to datasets.

Also, I wouldn't get hung up on L2S being "aimed at rapid development". This makes it sound like a prototyping tool. We're finding it to be an industrial strength tool. This might be contrary to what Microsoft might now be saying about it, since they would rather people use EF.

Randy

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.net – Entity Framework vs LINQ to SQL

LINQ to SQL only supports 1 to 1 mapping of database tables, views, sprocs and functions available in Microsoft SQL Server. It's a great API to use for quick data access construction to relatively well designed SQL Server databases. LINQ2SQL was first released with C# 3.0 and .Net Framework 3.5.

LINQ to Entities (ADO.Net Entity Framework) is an ORM (Object Relational Mapper) API which allows for a broad definition of object domain models and their relationships to many different ADO.Net data providers. As such, you can mix and match a number of different database vendors, application servers or protocols to design an aggregated mash-up of objects which are constructed from a variety of tables, sources, services, etc. ADO.Net Framework was released with the .Net Framework 3.5 SP1.

This is a good introductory article on MSDN: Introducing LINQ to Relational Data

C# – LINQ query on a DataTable

You can't query against the DataTable's Rows collection, since DataRowCollection doesn't implement IEnumerable<T>. You need to use the AsEnumerable() extension for DataTable. Like so:

var results = from myRow in myDataTable.AsEnumerable()
where myRow.Field<int>("RowNo") == 1
select myRow;

And as @Keith says, you'll need to add a reference to System.Data.DataSetExtensions

AsEnumerable() returns IEnumerable<DataRow>. If you need to convert IEnumerable<DataRow> to a DataTable, use the CopyToDataTable() extension.

Below is query with Lambda Expression,

var result = myDataTable
    .AsEnumerable()
    .Where(myRow => myRow.Field<int>("RowNo") == 1);

Best Answer

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.net – Entity Framework vs LINQ to SQL

C# – LINQ query on a DataTable

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