DataFiled Parent Id Other thn null?

[Mahesh]

Hi,
Thanks for Telerik team for making such wonderful tree control.
Where you can bind hierarchical data easily.
But I observed that the value for DataField Parent Id should be atleast one null value if the datatype is varchar.
Can I give 0 or any other value?
I don't want null values.
Thanks in advance.
-Mahesh