Newbie needs help on Undeclared Web Field

[justphilip]

My first venture into Web Projects, a completely coded class example project is not working. The instructions call for just typing “HiddenField – DiscountHiddenField” in a table cell. I am now receiving DiscountHiddenField not declared.

Is there a missing instruction that I need? TIA jp

            ' Save the discount total in a label
            DiscountHiddenField.Value = DiscountTotalDecimal.ToString()



        ' Check for existing value for the discount total.
        With DiscountHiddenField
            If IsPostBack And .Value <> "" Then
                DiscountTotalDecimal = Decimal.Parse(.Value)
            End If
        End With

Severity Code Description Project File Line Suppression State
Error BC30451 'DiscountHiddenField' is not declared. It may be inaccessible due to its protection level. Chapter 9 HandsOn d:\documents\visual studio 2017\Projects for the Web\Chapter 9 HandsOn\Chapter 9 HandsOn\My Project\Default.aspx.vb 38 Active
Error BC30451 'DiscountHiddenField' is not declared. It may be inaccessible due to its protection level. Chapter 9 HandsOn d:\documents\visual studio 2017\Projects for the Web\Chapter 9 HandsOn\Chapter 9 HandsOn\My Project\Default.aspx.vb 66 Active

[justphilip]

Do I need to add declaration to make my example code work? TIA JP

'Declaration
<ControlValuePropertyAttribute("Value")> _
Public Class HiddenField _
	Inherits Control _
	Implements IPostBackDataHandler
End Class

Example project:

' Project:          CH 9 HandsOn
' Programmer:       Bradley/Millspaugh 
' Date:             Jun 2010
' Description:      A Web site to calculate the extended price for books sold,
'                   at discount, and the discounted amount. Calculates and displaysthe total discounts.
'                   Uses validator controls for input validation.
' Folder            Ch09HansOn                  
' Exercise:         From "Programming in Visual Basic 2010" by Julia C. Bradley & Anita C. Millspaugh
'                   On page 286 - 393.
'
' Partial class name and inherits problem? _Default vs _Default_aspx yielded undeclared variable errors!
Partial Class _Default
    Inherits System.Web.UI.Page

    Private DiscountTotalDecimal As Decimal
    Const DISCOUNT_RATE_DECIMAL As Decimal = 0.15D

    Protected Sub SubmitButton_Click(sender As Object, e As EventArgs) Handles SubmitButton.Click
        ' Calculate values for sale.
        Dim QuantityInteger As Integer
        Dim PriceDecimal, EtendedPriceDecimal As Decimal
        Dim DiscountDecimal, DiscountPriceDecimal As Decimal
        ErrorMessageLabel1.Text = String.Empty
        Try
            ' Convert input values to numeric variables.
            QuantityInteger = Integer.Parse(QuantityTextBox.Text)
            PriceDecimal = Decimal.Parse(PriceTextBox.Text)

            ' Calculate values for sale.
            EtendedPriceDecimal = QuantityInteger * PriceDecimal
            DiscountDecimal = EtendedPriceDecimal * DISCOUNT_RATE_DECIMAL
            DiscountPriceDecimal = EtendedPriceDecimal - DiscountDecimal

            ' Add to the discount total
            DiscountTotalDecimal += DiscountPriceDecimal

            ' Save the discount total in a label
            DiscountHiddenField.Value = DiscountTotalDecimal.ToString()

            ' Format and display answers.
            ExtendedPriceTextBox.Text = EtendedPriceDecimal.ToString("C")
            DiscountTextBox.Text = DiscountDecimal.ToString("N")
            DiscountedPriceTextBox.Text = DiscountPriceDecimal.ToString("C")


        Catch ex As Exception
            ErrorMessageLabel1.Text = "Unable to calculate. Check for numeric values."
        End Try

    End Sub

    Protected Sub ClearButton_Click(sender As Object, e As EventArgs) Handles ClearButton.Click
        ' Clear previous amounts from the page.
        QuantityTextBox.Text = ""
        TitleTextBox.Text = ""
        PriceTextBox.Text = ""
        ExtendedPriceTextBox.Text = ""
        DiscountTextBox.Text = ""
        '    DiscountlHiddenField.Text = ""
        DiscountTotalLabel.Text = ""
        ErrorMessageLabel1.Text = ""
    End Sub

    Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        ' Check for existing value for the discount total.
        With DiscountHiddenField
            If IsPostBack And .Value <> "" Then
                DiscountTotalDecimal = Decimal.Parse(.Value)
            End If
        End With

    End Sub
    Private Sub SummaryButton_Click(sender As Object, e As EventArgs) Handles SummaryButton.Click
        ' Displaythe total discount.

        ' DiscountTotalLabel.Text = "Total Discounts: $" & DiscountTotalHiddenField.Value
        DiscountTotalLabel.Text = "Total Discounts: $" & DiscountTotalDecimal.ToString

    End Sub

End Class

[KGComputers]

Did you add a hidden field control in your aspx markup same as the textbox and label controls?

[justphilip]

Thanks for your response. There were no instructions for adding a hidden field control in my aspx markup same as the textbox and label controls. I do not know enough to do so!
aspx markup? Would that entail using 'Markup Fragment' tool, if so how do you use it? TIA JP

[techgnome]

Probably not... you would open the aspx page which contains all the weby stuff... the HTML and other front-end elements. That's where you need to add the field to. Then mark it as hidden. Once you've done that, you should then be able to access it from the .codebehind.vb file (where your code should be) with out any further issues.

-tg

[justphilip]

Lacking experience and no guidance from the textbook, I simply typed “HiddenField – DiscountHiddenField” in a table cell. I now see a tool 'Hiddenfield' which removed the previous errors, and now I have an issue with the several usages of 'Value':

Severity Code Description Project File Line Suppression State
Error BC30456 'Value' is not a member of 'HtmlForm'. Chapter 9 HandsOn d:\documents\visual studio 2017\Projects for the Web\Chapter 9 HandsOn\Chapter 9 HandsOn\My Project\Default.aspx.vb 40 Active

Progress is slow but moving! TIA JP

[justphilip]

I suspect part of my problem is that the textbook was written for VS 2010 and I am using VS community 2017.

Having looked at internet sample, it would appear that 'value' needs to be built into the source code - something I know nothing about. JP

<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="Default.aspx.vb" Inherits="Chapter_9_HandsOn._Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>