VB.NET SQL Connection fill GridView

     Imports system.data.sqlclient
     Imports system.data

         Dim cn As New SqlConnection
        Dim sql As String
        Dim ds As New DataSet
        Dim da As New SqlDataAdapter
        cn = New SqlConnection("server=localhost;database=NLAB 2012-2013;integrated security=true")
        sql = "select * from mainmaster"
        Dim cm As New SqlCommand(sql, cn)
        da = New SqlDataAdapter(cm)
        da.Fill(ds)
        GridView1.DataSource = ds.Tables(0)
        GridView1.DataBind()