Dependency Injection in .NET with examples?

Question

Can someone explain dependency injection with a basic .NET example and provide a few links to .NET resources to extend on

Answer 1

I've got Dependency Injection with a really simple example like this.

See the class below, you'll get the whole idea. As you see unless you supply file it will use the default one settings file, but you can set a settings file and then the class will use it.

Public Class ProcessFile

Private _SettingsFile As String = "settings.bin"

Public Sub New()
End Sub

Public Sub New(settings As String)
_SettingsFile= settings
End Sub

Public Function ReadFile() As String 
'Do stuff based on the settings stored in the _SettingsFile 
End Function

End Class

Obviously this is the most basic case. In real world you can do the same thing with class types, such as you've got Database Layer and you can switch the underlying database dll by doing dependency injection and you code will work with any database as soon as you can provide the valid class (a class which implements the interface you are using).

After got the basic you can do this on larger scope and totally independent from the application by using DI frameworks like unity.