怎样treeview1的节点名不重复！！

[lizy_fish]

Dim i As Integer
Me.TreeView1.Nodes.Add("教室")
Dim ds1 As New Data.DataSet
Dim sql11 As String
sql11 = "select 教学楼号 from 教室 "
Try
Dim adapter11 As SqlClient.SqlDataAdapter = New SqlClient.SqlDataAdapter(sql11, myconn)
adapter11.Fill(ds1, "11")
Catch ex As Exception
MsgBox(ex.Message)
End Try
For i = 0 To ds1.Tables("11").Rows.Count - 1
Me.TreeView1.Nodes(0).Nodes.Add(ds1.Tables("11").Rows(i).Item("教学楼号"))
Next