SQL Data Convertion Error??

HI,

I'm encouter some data convertion string problem especially during database update use asp.net (vb.net). Please help advice how can i solve the error??

I guess integer value need convert to string before able execute update function..

The error i get: -

1) failed to convert nvarchar to int

2) Convertion string is not in correct format...

let say i drag a textbox (txtquantity) and allow input and click update (with call procedure) updatexx set quantity=2 select from YY.

Wondering if i missed some important code??

Another data converting errorsituation is: let say i create a class call "AA" then have properties quantity as string, sProductID as string

i retrieve the data

........function get info(by ProductID as string) 

If reader.Read() Then
            OrdInfo.quantity = reader("Quantity").ToString()
            OrdInfo.ProductID = reader("ProductID").ToString()

.....

sub update BB (byval aa as AA)

...

   command.Parameters.Add("@Quantity", Data.SqlDbType.Int)
        command.Parameters("@Quantity").Value = AA.quantity


        command.Parameters.Add("@ProductID", Data.SqlDbType.Int)
        command.Parameters("@ProductID").Value = AA.sProductID

Cheers:)