problem in set the Visible property of the first row of a datagridview to false

hi
i have a DataGridView in my form .its datasource is a DataTable .i want to set the first row's visible property to false
i use this command :

program run without any error but the first row remain visible.
only this row has this problem . if i select another row and set visibility to false it;s not has any problem .
please help me about it .