Calculating a Subtotal for Shopping Cart

[Sparky Arbuckle]

I'm trying to calculate the subtotal for each item the customer has in
the shopping cart. objDataReader("decPrice") is the price from my
database field called decPrice. The .8 is for a 20% discount. The
error I get is:

Compiler Error Message: BC30201: Expression expected.

What is the correct syntax for this operation? When I check the
compiler output there is a ~ underneath the &. Any help would be
greatly appreciated.

<!-- CODE SNIPPET -->

Dim strSubTotal as string = 0
Dim i as integer = 0
FOR i = 0 to gtCart.count -1
dim strItemID as string = ds.Tables("tblSCart").rows(i)("ItemID")
ds.Tables("tblSCart").rows(i)("Qty") = gtCart(strItemID)
strSubTotal = .8 * & objDataReader("decPrice")
NEXT

<!-- CODE SNIPPET -->

 

[Ken Dopierala Jr.]

Hi,

Try this:

strSubTotal = CStr(.8 * CDec(objDataReader("decPrice")))

Good luck! Ken.

 

[gaidar]

The error is here:

strSubTotal = .8 * & objDataReader("decPrice")

If you want to add ".8 *" as string do it in the following way:

strSubTotal = ".8 *" & objDataReader("decPrice")

But if you want to multiply the value of objDataReader("decPrice") by .8 and
then convert the value to string

strSubTotal = CType(0.8 * CType(objDataReader("decPrice"), Double), string)
Best regards,

Gaidar

 

[Sparky Arbuckle]

Thanks for the prompt reply Ken. Now I get a new error:

Exception Details: System.NullReferenceException: Object reference not
set to an instance of an object.

 

[Sparky Arbuckle]

Gaidar:

I get the same error when I try your example. Maybe more insight would
be had if I were to tell the group that I am binding this information
to a dataGrid?

 

[gaidar]

May be you will post complete code of the class?

 

[Sparky Arbuckle]

You got it:

Sub UpdateCookie(byRef gtCart as HashTable)

'Retrieve querystring parameters
Dim strDelete as string = Request.querystring("Delete")
Dim strAdd as string = Request.querystring("Add")

'If no changes to cookie then return
IF strDelete < " " and strAdd < " " THEN RETURN

IF strDelete > " " THEN
IF gtcart.Contains(strDelete) THEN
IF gtCart(strDelete) = 1 THEN
gtCart.remove(strDelete)
ELSE
gtCart(strDelete) = gtCart(strDelete)-1
END IF
ELSE
Response.Write("No such ASIN in cart: " & strDelete & "<br>")
RETURN
END IF
END IF

IF strAdd > " " THEN
IF gtCart.Contains(strAdd) THEN
gtCart(strAdd) = gtcart(strAdd) + 1
ELSE
gtCart(strAdd) = 1
END IF
END IF

'Delete cookie if empty. This eliminates empty "ghost" key.
IF gtCart.count = 0 THEN
Response.Cookies(MyCookieName).Expires = Now.AddDays(-1)
RETURN
END IF

'Write HashTable back to cookie
Dim MyCookie as new httpCookie(MyCookieName)

Dim iCount as integer = 0
Dim objConn as new
OLEDBConnection(ConfigurationSettings.AppSettings("StrConnection"))
Dim strSQL as string = "SELECT ASIN, strTitle, strArtist, decPrice,
strLabel, intNumberDisks, dtReleaseDate, strReview, strImageDir " & _
"FROM tblDescription WHERE "

FOR EACH myItem as DictionaryEntry in gtCart
iCount = iCount + 1
MyCookie.Values(myItem.Key) = myItem.Value

strSQL += "ASIN= '" & myItem.Key & "'"

IF iCount < gtCart.Count
strSQL += " OR "

ELSE

strSQL += ";"
END IF

Response.Cookies("Customer")("Quantity") = MyItem.Value

NEXT

Dim objDataReader as OLEDBDataReader
objConn.Open()

Dim objCommand as new OLEDBCommand(strSQL,objConn)

Dim myCommand as new OleDbDataAdapter(strSQL, objConn)
myCommand.Fill(ds, "tblSCart")
ds.Tables("tblSCart").Columns.Add("Qty")

Dim strSubTotal as string = 0
Dim i as integer = 0
FOR i = 0 to gtCart.count -1
dim strASIN as string =
ds.Tables("tblSCart").rows(i)("ASIN")
ds.Tables("tblSCart").rows(i)("Qty") = gtCart(strASIN)
strSubTotal = ".8 *" & objDataReader("decPrice")
NEXT

lblShipping.text = 0
lblSubTotal.text = strSubTotal
lblGrandTotal.text = 0

dgSCart.DataSource = ds.Tables("tblScart").DefaultView
dgSCart.DataBind()

'Write cookie to page
Response.Cookies.Add(MyCookie)
Response.Cookies(MyCookieName).Expires = Now.AddDays(30)

FOR EACH myItem as DictionaryEntry in gtCart
MyCookie.Values(myItem.Key) = myItem.Value

NEXT

END Sub