Hello, I get this error when trying to compile with winforms
_________________________
Compiling...

Microsoft (R) C# Compiler Version 7.00.8905 [NGWS runtime 2000.14.1812.10]
Copyright (C) Microsoft Corp 2000. All rights reserved.

system.winforms.dll: error CS0011: Referenced class
'System.WinForms.Control' has unknown base class or interface
'System.ComponentModel.MarshalByRefComponent'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'Microsoft.Win32.Interop.IOleControl'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'Microsoft.Win32.Interop.IOleObject'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'Microsoft.Win32.Interop.IOleInPlaceObject'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'Microsoft.Win32.Interop.IOleInPlaceActiveObject'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'Microsoft.Win32.Interop.IViewObject2'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'Microsoft.Win32.Interop.IPersist'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'Microsoft.Win32.Interop.IPersistStreamInit'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'Microsoft.Win32.Interop.IPersistPropertyBag'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'Microsoft.Win32.Interop.IPersistStorage'
system.winforms.dll: error CS0011: Referenced class
'System.WinForms.RichControl' has unknown base class or interface
'System.ComponentModel.ISynchronizeInvoke'
_____________________

Here's the little source code im using.
----------------------------------------
namespace Microsoft.Samples.WinForms.Cs.SimpleHelloWorld {
using System;
using System.WinForms;

public class SimpleHelloWorld : Form {

public static int Main(string[] args) {
Application.Run(new SimpleHelloWorld());
return 0;
}

public SimpleHelloWorld() {
this.Text = "Hello World";
}
}
}
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Any ideas?