The following code,

using System;
using System.Windows.Forms;

class MdiBox : Form
{
MdiBox()
{
IsMdiContainer = true;
}

static void Main(String[] args)
{
Application.Run(new MdiBox());
}
};

produces
ptah@foo:~$ cscc -g -lSystem -lSystem.Windows.Forms -winforms -o test.exe test.cs
ptah@foo:~$ ilrun test.exe
Uncaught exception: System.NullReferenceException: The value 'null' was found where an instance of a
n object was required
        at System.Windows.Forms.Control.CreateHandle() in ./Control.cs:2046
        at System.Windows.Forms.Control.CreateControlInner() in ./Control.cs:1969
        at System.Windows.Forms.Control.CreateControlInner() in ./Control.cs:1978
        at System.Windows.Forms.Control.CreateControl() in ./Control.cs:1960
        at System.Windows.Forms.Control.OnVisibleChanged(EventArgs) in ./Control.cs:5241
        at System.Windows.Forms.Form.OnVisibleChanged(EventArgs) in ./Form.cs:1369
        at System.Windows.Forms.Control.SetVisibleCore(Boolean) in ./Control.cs:3377
        at System.Windows.Forms.ScrollableControl.SetVisibleCore(Boolean) in ./ScrollableControl.cs:
282
        at System.Windows.Forms.Form.SetVisibleCore(Boolean) in ./Form.cs:1551
        at System.Windows.Forms.Control.set_Visible(Boolean) in ./Control.cs:1796
        at System.Windows.Forms.Control.Show() in ./Control.cs:3390
        at System.Windows.Forms.Application.RunMessageLoop(ApplicationContext) in ./Application.cs:3
88
        at System.Windows.Forms.Application.Run(Form) in ./Application.cs:576
        at MdiBox.Main(String[]) in test.cs:13

on windows (using Cygwin); Linux/BSD not affected.