I tried this coding. Its working well.
cmdq2.Dispose()
cmdq2.Parameters.Clear()
cmdq2.Connection = con
cmdq2.CommandType = CommandType.StoredProcedure
cmdq2.CommandText = "sp_inout"
cmdq2.Parameters.Add("@companyid", SqlDbType.BigInt).Value = Session("maincompanyid")
cmdq2.Parameters.Add("@contactid", SqlDbType.BigInt).Value = Session("Customer_id")
cmdq2.Parameters.Add("@invoiceid", SqlDbType.Int).Value = cash_invid
cmdq2.Parameters.Add("@currency", SqlDbType.Char).Value = currency
Dim idr As SqlDataReader = cmdq2.ExecuteReader()
If idr.Read() Then
Dim item As ListItem = New ListItem()
item.Text = idr("invoiceno").ToString()
item.Value = idr("invoiceid").ToString()
ddlinv.Items.Add(item)
End If