Global Variables lose value in another event

Question

I have following global variables

Dim cardNumber As String
Dim txnAmount As String
Dim TerminalID As String
Dim CurrencyCode As String

And Values are assigned on a click Event from the result set returned from SP

dsCards = Utilities.GetVirtualResultNew(txtCardNumber.Text.Trim)
grdTransactionResultSearch.DataSource = dsCards
grdTransactionResultSearch.DataBind()
cardNumber = IIf(IsDBNull(dsCards.Tables(0).Rows(0).Item("pan")), "", dsCards.Tables(0).Rows(0).Item("pan"))
txnAmount = IIf(IsDBNull(dsCards.Tables(0).Rows(0).Item("TotalAmount")), "", dsCards.Tables(0).Rows(0).Item("TotalAmount"))
TerminalID = IIf(IsDBNull(dsCards.Tables(0).Rows(0).Item("TerminalID")), "", dsCards.Tables(0).Rows(0).Item("TerminalID"))
CurrencyCode = IIf(IsDBNull(dsCards.Tables(0).Rows(0).Item("CurrencyCode")), "", dsCards.Tables(0).Rows(0).Item("CurrencyCode"))

I Debugged the code and I can see the values are assigned to them but when I try to access them in another button click event, They are empty

Here is my button click event where These variables are empty

Protected Sub btnAuthorize_Click(sender As Object, e As EventArgs) Handles btnAuthorize.Click
  Utilities.InsertAuthorizedTransactions(cardNumber, txnAmount, TerminalID, CurrencyCode)
  Label1.Visible = True
END Sub

Whats the problem with my code?

When you say "global" where are they actually defined – Matt Wilko Aug 24 '15 at 07:48 — Matt Wilko, Aug 24 '15 at 07:48
Inside the class, before any methods/events – Nuke Aug 24 '15 at 07:49 — Nuke, Aug 24 '15 at 07:49

score 0 · Accepted Answer · edited May 23 '17 at 11:58

When a button is clicked, then a postback is performed (What is a postback?) which in this case will re-initliase your variables.

The preferred option is probably to store your variables in ViewState (What is ViewState?) in your first button click:

ViewState("cardNumber") = "foo"
ViewState("txnAmount") = "bar"
'etc.

And then access them in your second click.

Note also that you should not use the IIF function in VB.NET but you should instead use the If Operator

Global Variables lose value in another event

1 Answers1