put value in textbox from database

hi guys
iam doing database. this is the code i written to put minvalue of column "p" to text box.
but after showing datable.iam not getting that value to text box. anybody give solution.

1.cmdstr = "select * from ratio"
2.'cmdstr = "select min(p) from ratio"

individually the two queries working fine

strcon = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & "H:\venky.accdb" & ""
con = New OleDbConnection(strcon)
con.Open()
cmdstr = "select * from ratio"
'cmdstr = "select min(p) from ratio"
cmd = New OleDbCommand(cmdstr, con)
datardr = cmd.ExecuteReader()
dt = New DataTable()
dt.Load(datardr)
'dt.DefaultView.Sort = "p"
'smin = dt.Rows(0).Item("p")
'TextBox1.Text = smin.ToString
Me.DataGridView1.DataSource = dt
TextBox1.Text = dt.Compute("MIN(P)").tostring