.NET (Core and Framework)

private void Form1_Load(object sender, System.EventArgs e)
{
	DataTable tbl = new DataTable();
	tbl.Columns.Add( "TwoState", typeof(bool) );
	tbl.Rows.Add( new object[] { true } );
	tbl.Rows.Add( new object[] { false } );
	this.dataGrid1.DataSource = tbl;

	DataGridTableStyle tableStyle = typeof(DataGrid).GetField( 
		"myGridTable",
		System.Reflection.BindingFlags.Instance | 
		System.Reflection.BindingFlags.NonPublic).GetValue( this.dataGrid1 ) 
		as DataGridTableStyle;

	(tableStyle.GridColumnStyles[ "TwoState" ] as DataGridBoolColumn).AllowNull = false;
}