public void Properties()
{
var ds = new DataSet();
Assert.Equal(string.Empty, ds.Namespace);
ds.Namespace = null; // setting null == setting ""
Assert.Equal(string.Empty, ds.Namespace);
Assert.Equal(string.Empty, ds.Prefix);
ds.Prefix = null; // setting null == setting ""
Assert.Equal(string.Empty, ds.Prefix);
}