c# - Import of SVsServiceProvider not working in custom editor

Question

I created a custom editor for a WinForms component which implements UITypeEditor and works fine. The editor should load information from the currently opened solution and I think this should be done with DTE from the VisualStudio SDK.

According to a MSDN article (http://msdn.microsoft.com/en-us/library/ee834473(v=vs.110).aspx) I implemented this exactly like this:

internal class TreeViewTypeEditor : UITypeEditor
{
     [Import]
     internal SVsServiceProvider ServiceProvider = null;

     protected override Control GetEditControl(ITypeDescriptorContext context, object value)
     {
         // ServiceProvider is NULL here!
         DTE dte = (DTE)ServiceProvider.GetService(typeof(DTE));
     }
}

ServiceProvider will always be null but why? What am I doing wrong?