C# 4 and .NET 4

1066 ❘ ChaPTer 36 business ApplicAtiOns with wpf
}
}
public IEnumerable Years
{
get
{
F1DataContext.Data = data;
return (from r in data.Races
orderby r.Date ascending
select
new Championship
{
Year = r.Date.Year,
}).Distinct();
}
}
code snippet Formula1Demo/TreeUC.xaml.cs
The Championship class has a simple automatic property for the year. The Races property is of type
Lazy. The Lazy class is new with .NET 4 for lazy initialization. With a
TreeView control, this class comes in very handy. If the data behind the tree is large and you do not want
to load the full tree in advance, but only when a user makes a selection, lazy loading can be done. With
the constructor of the Lazy class, a delegate Func is used. With this delegate,
IEnumerable needs to be returned. The implementation of the Lambda expression, assigned to
the delegate, uses a LINQ query to create a list of F1Race objects that have the Date and Country
property assigned:
public class Championship
{
public int Year { get; set; }
public Lazy Races
{
get
{
return new Lazy(() =>
{
return from r in F1DataContext.Data.Races
where r.Date.Year == Year
orderby r.Date
select new F1Race
{
Date = r.Date,
Country = r.Circuit.Country
};
});
}
}
}
code snippet Formula1Demo/Championship.cs
The F1Race class again defines the Results property that uses the Lazy type to return a list of
F1RaceResult objects:
public class F1Race
{
public string Country { get; set; }
public DateTime Date { get; set; }
public Lazy Results
{
get
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