Sql – LINQ to SQL: Lazy loading an association

linqlinq-to-sqlnetsql

How can I lazy load an association (EntitySet) in LINQ to SQL? You can't set Delay Loaded on Associations in the designer, and I couldn't find a DBML attribute for it either. I looked at DataLoadOptions to see if there was a way to lazy load them that way, but DataLoadOptions really just provides a way to mold the SQL that is generated for properties and associations (and force loading of lazy loaded properties).

This is a very important feature for us, as we have a pretty heavy object graph that gets pushed to the DB. When loading some of the top level objects, I don't want to load their associated sub-entities until the user actually requests that data. It's easy to do for individual properties, but I can't find a way to do it for associations. The EntitySet collection seems to support the concept, so there has to be a way.

Best Answer

Lazy loading is enabled by default in Linq to SQL - EntitySet and EntityRef are used support this feature.

Related Solutions

.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

Related Solutions

.net – Entity Framework vs LINQ to SQL

C# – LINQ query on a DataTable

Related Topic