Porque no usas un datatable directamente.
Código vb.net:
Ver originalUsing cn As New SqlConnection(CadenaConexion)
Dim query As String = "SELECT * from T_Descicion"
Using cmd As New SqlCommand(query, cn)
Dim da As New SqlDataAdapter(cmd)
Dim dt As New DataTable
da.Fill(dt)
ComboBox1.DataSource = dt
cbTipo.DisplayMember = "Tipo_descicion"
cbTipo.ValueMember = "Cod_Descicion"
End Using