NotImplementedException in Silverlight and IronPython - wpf

Question

i'm hosting IronPython Scripts in one Silverlight Application and i want to run the script and get one System.Windows.Controls.TextBlock object.
so i use this ironPython code:
import clr
clr.AddReferenceByName("System.Windows.Controls, Version=2.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35")
from System.Windows.Controls import *
tb = TextBlock()
i'm being able to add the reference, but, when i import System.Windows.Controls i get a System.NotImplementedException.
The same happens if i try with "import wpf"
i'm using Silverlight 4 and IronPython 2.7.1 beta2
and this is the code to run the script:
Dim engine = IronPython.Hosting.Python.CreateEngine
Dim scope = engine.CreateScope()
Dim source = engine.CreateScriptSourceFromString(CodeTB.Text)
source.Execute(scope)
ResultLB.Items.Add(scope.GetVariable("hello"))
If scope.ContainsVariable("tb") Then
GuiStack.Children.Add(scope.GetVariable("tb"))
End If
Here is the Stack Trace of the exception:
en Microsoft.Scripting.PlatformAdaptationLayer.FileExists(String path)
en IronPython.Runtime.Importer.LoadModuleFromSource(CodeContext context, String name, String path)
en IronPython.Runtime.Importer.LoadPackageFromSource(CodeContext context, String name, String path)
en IronPython.Runtime.Importer.LoadFromDisk(CodeContext context, String name, String fullName, String str)
en IronPython.Runtime.Importer.ImportFromPathHook(CodeContext context, String name, String fullName, List path, Func`5 defaultLoader)
en IronPython.Runtime.Importer.ImportFromPath(CodeContext context, String name, String fullName, List path)
en IronPython.Runtime.Importer.ImportTopAbsolute(CodeContext context, String name)
en IronPython.Runtime.Importer.ImportModule(CodeContext context, Object globals, String modName, Boolean bottom, Int32 level)
en IronPython.Modules.Builtin.__import__(CodeContext context, String name, Object globals, Object locals, Object fromlist, Int32 level)
en Microsoft.Scripting.Interpreter.FuncCallInstruction`7.Run(InterpretedFrame frame)
en Microsoft.Scripting.Interpreter.Interpreter.Run(InterpretedFrame frame)
en Microsoft.Scripting.Interpreter.LightLambda.Run7[T0,T1,T2,T3,T4,T5,T6,TRet](T0 arg0, T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6)
en IronPython.Runtime.Importer.ImportLightThrow(CodeContext context, String fullName, PythonTuple from, Int32 level)
en IronPython.Runtime.Importer.Import(CodeContext context, String fullName, PythonTuple from, Int32 level)
en IronPython.Runtime.Operations.PythonOps.ImportStar(CodeContext context, String fullName, Int32 level)
en Microsoft.Scripting.Interpreter.ActionCallInstruction`3.Run(InterpretedFrame frame)
en Microsoft.Scripting.Interpreter.Interpreter.Run(InterpretedFrame frame)
en Microsoft.Scripting.Interpreter.LightLambda.Run2[T0,T1,TRet](T0 arg0, T1 arg1)
en IronPython.Compiler.PythonScriptCode.RunWorker(CodeContext ctx)
en IronPython.Compiler.PythonScriptCode.Run(Scope scope)
en IronPython.Compiler.RuntimeScriptCode.InvokeTarget(Scope scope)
en IronPython.Compiler.RuntimeScriptCode.Run(Scope scope)
en Microsoft.Scripting.SourceUnit.Execute(Scope scope, ErrorSink errorSink)
en Microsoft.Scripting.SourceUnit.Execute(Scope scope)
en Microsoft.Scripting.Hosting.ScriptSource.Execute(ScriptScope scope)
en TestApp2.MainPage.ExecuteButton_Click(Object sender, RoutedEventArgs e)
en System.Windows.Controls.Primitives.ButtonBase.OnClick()
en System.Windows.Controls.Button.OnClick()
en System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
en System.Windows.Controls.Control.OnMouseLeftButtonUp(Control ctrl, EventArgs e)
en MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)
And here is the all the source code
Thankyou for everything :)

Answer 1

It should work without any AddReference:
import clr
from System.Windows.Controls import TextBlock
tb = TextBlock()

Answer 2

Thank You, Lukas, the article was very helpful, now the problem is fixed.
Here's my new source code
Dim setup As ScriptRuntimeSetup = Python.CreateRuntimeSetup(Nothing)
setup.HostType = GetType(Microsoft.Scripting.Silverlight.BrowserScriptHost)
Dim runtime As New ScriptRuntime(setup)
Dim engine = IronPython.Hosting.Python.GetEngine(runtime)
Dim scope = engine.CreateScope()
Dim uri As New Uri("System.Windows.Controls.dll", UriKind.Relative)
Dim sri As StreamResourceInfo = Application.GetResourceStream(uri)
Dim ap As New AssemblyPart
Dim asm As Assembly = ap.Load(sri.Stream)
runtime.LoadAssembly(asm)
Dim assamblies As String() = {"mscorlib", "System", "System.Windows", "System.Windows.Browser", "System.Net"}
For Each item In assamblies
runtime.LoadAssembly(runtime.Host.PlatformAdaptationLayer.LoadAssembly(item))
Next
Dim source = engine.CreateScriptSourceFromString(CodeTB.Text, Microsoft.Scripting.SourceCodeKind.Statements)
source.Execute(scope)
ResultLB.Items.Add(scope.GetVariable("hello"))
If scope.ContainsVariable("tb") Then
GuiStack.Children.Add(scope.GetVariable("tb"))
End If