Creating Data Layer
1) Before we generate our data layer we must create a new connection in Server Explorer which points to Northwind database.
2) We will now generate our data layer using LINQ To SQL. To do this you need to add a new item to the data layer project of type LINQ to SQL Classes. We will name it Northwind as shown below.
3) After adding a LINQ to SQL Class we are presented with a designer surface. Here we can simply drag the tables which will become part of our data layer. For this article we will drag all tables on the designer by selecting them all in one go. Our designer should look like this after dragging all tables on it.
4) We should now build our solution to make sure everything is okay. And that’s it. We have successfully generated our data layer. In Solution Explorer we can see that we have two new files namely Northwind.dbml.layout and Northwind.designer.cs. We can also see that references required to compile and run our code have been added by Visual Studio.
The .cs file contains the code for our data layer. Let’s examine the code that has been generated for us. We will look at the Region class.
[Table(Name="dbo.Region")]
public partial class Region : INotifyPropertyChanging, INotifyPropertyChanged
The class itself is decorated with Table attribute and the Name property has been assigned the actual table name we have in our database. Region class also implements INotifyPropertyChanging and INotifyPropertyChanged interfaces. These interfaces are used for databinding. Region class also contains one property per column. Let’s look at the RegionDescription property.
[Column(Storage="_RegionDescription", DbType="NChar(50) NOT NULL",
CanBeNull=false)]
public string RegionDescription
{
get
{
return this._RegionDescription;
}
set
{
if ((this._RegionDescription != value))
{
this.OnRegionDescriptionChanging(value);
this.SendPropertyChanging();
this._RegionDescription = value;
this.SendPropertyChanged("RegionDescription");
this.OnRegionDescriptionChanged();
}
}
}
Columns are decorated with Column attribute and values are passed in for Storage, DbType and CanBeNull which indicates if the column can be null or not.