DataGrid Hierarchy checkbox-indeterminate

[LMGeds]

Good day,
I have a question about DataGrid Hierarchy. As shown below I want to see DataGrid Hierarchy with checkbox.
Unfortunately, I cannot activate the checkbox-indeterminate? How can I change settings so that it is activated?

just like here:

[enchev]

You need to bind to bool? and set TriState to true:

Blazor checkbox component with optional tri-state support

[LMGeds]

Thank you for your answer, I set TriState to true. How can I define the bool value in my case?

[enchev]

You can set TValue="bool?".

[LMGeds]

I used it doesn't work.
here is the whole code:

[enchev]

Well, you might want to have tri-state CheckBox in the header instead for items.

[LMGeds]

Yes, that will work for me too. But I get the args error in the header area.