Adding a value to a Label that already has a value (Numeric / Currency)

Question

Hi Great People

I am having a issue with adding a value to a value in a Label.

Basically When I select Data from my Database. My Labels are filled with Currency Values. ( LbSubTotal ), ( LbVAT ), ( LbNet )

I also have two textboxes ( TxtWaitingTime ) , ( TxtTolls )

Is what I am trying to achieve is, when I need to enter a value into One or Both of the textboxes, I then want to add the value of the textbox(s) to a Label ( LbNet).

This means I want to add the value of the two textboxes (if any value(s) have been inserted). to the label LbNet.

I have tried Code that was written for me by a great person ( LesHay ) I have tried manipulating LesHay's Code to suit the issue I have. to no Avail.
The Code I have...

Private Sub TxtWaitingTime_TextChanged(sender As Object, e As EventArgs) Handles TxtWaitingTime.TextChanged, TxtTolls.TextChanged  
  
        Dim tb As TextBox = DirectCast(sender, TextBox)  
        If Not tb.Name = "TxtWaitingTime" AndAlso Not tb.Name = "TxtTolls" AndAlso Not tb.Text.StartsWith("") Then  
            tb.Text = "£" & tb.Text  
            tb.SelectionLength = 0  
            tb.SelectionStart = tb.Text.Length  
  
        End If  
        SetTB()  
    End Sub  
  
    Sub SetTB()  
        Dim tot As Decimal = 0D  
        For Each c As Control In GroupBox4.Controls  
            If c.GetType = GetType(TextBox) Then  
                tot += GetDec(c.Text)  
            End If  
        Next  
  
        'If TxtWaitingTime.Text = Nothing Then  
        '    TxtWaitingTime.Text = "0.00"  
        'ElseIf TxtTolls.Text = Nothing Then  
        '    TxtTolls.Text = "0.00"  
        'End If  
  
        TxtWaitingTime.Text = GetDec(TxtWaitingTime.Text).ToString + TxtTolls.Text = GetDec(TxtTolls.Text).ToString("£0.00")  
  
        LbNet.Text = GetDec(TxtWaitingTime.Text) + GetDec(TxtTolls.Text) + tot.ToString("£0.00")  
  
  
    End Sub  

With this code I keep getting the wrong answer or the TxtWaitingTime puts a value of " False "

Please can any of you great People help.

Kind Regards
Gary

Answer 1

Hi

You are finding the intricacies of writing code :) The issue as I understand it is that you are trying to add to a final calculation. This is always something I would avoid. My approach in such a case is to include the two values in the main calculation having initially set them to zeroes first. During other data being calculated, with these being zero, the Net total is the same as though they were not there. Now, when the values are changed in the TextBoxes, do the entire calculation again - this means the Net value will always be correct.
Of course, if you do not already have a Sub of some sort that you use for overall calculation, it would mean alterations.
It would probably be worth the effort, as the only other way I can think of is that you track every TextBox change and 'UNDO' the changes as needed - this is NOT a trivial way to go,
Now, the question is: do you have a common Calculation Sub?

Here is a sample of what I am saying:

Option Strict On  
Option Explicit On  
Public Class Form1  
 Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load  
 ' add a few values - these would be your  
 ' own calculated values or user input.  
 TextBox1.Text = 0.ToString("c2")  
 TextBox2.Text = 0.ToString("c2")  
 TextBox3.Text = (1.45).ToString("c2")  
 TextBox4.Text = (2.45).ToString("c2")  
 TextBox5.Text = (3.55).ToString("c2")  
 TextBox6.Text = (4.55).ToString("c2")  
 Calc()  
 End Sub  
 Sub Calc()  
 Dim tot As Decimal = 0.0D  
 For Each gbc As Control In Controls  
 If gbc.GetType = GetType(GroupBox) Then  
 For Each c As Control In gbc.Controls  
 If c.GetType = GetType(TextBox) Then  
 tot += GetDecimal(c.Text.Replace("£"c, String.Empty))  
 End If  
 Next  
 End If  
 Next  
 Label2.Text = tot.ToString("c2")  
 End Sub  
 Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged, TextBox2.TextChanged  
 Calc()  
 End Sub  
 Function GetDecimal(s As String) As Decimal  
 Dim v As Decimal = 0.0D  
 If Decimal.TryParse(s, v) Then Return v  
 Return 0.0D  
 End Function  
End Class  

Answer 2

Hi
Here is an example. Here, use a Label with Net amount (string value), and add both values from 2 textboxes below. However, I suspect that you will not be happy doing this. The values are constantly being added to every time a TextBox changes. I feel you would be better to have a 'Calc' button once values are entered, and, that you repeat the entire calculation - otherwise the point about constant changes will occur (slightly differently)

Public Class Form1  
 Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged, TextBox2.TextChanged  
 Dim tot As Decimal = 0.00  
 For Each c As Control In GroupBox4.Controls  
 If c.GetType = GetType(TextBox) Then  
 tot += GetDecimal(c.Text)  
 End If  
 Next  
 Dim labVal As Decimal = GetDecimal(Label2.Text.Replace("£"c, String.Empty))  
 Label2.Text = (labVal + tot).ToString("£0.00")  
' or,  Label2.Text = (labVal + tot).ToString("c2")  
 End Sub  
 Function GetDecimal(s As String) As Decimal  
 Dim v As Decimal = 0.00  
 If Decimal.TryParse(s, v) Then Return v  
 Return 0.00  
 End Function  
End Class  

Answer 3

Hi LesHay

Thank you for getting back to me. I have tried your code naming my own labels and textboxes.
And you are right there is a slight problem. As I enter number(s) / Numeric values and even decimal point adds to my Label ( LbNet )

So I tried your suggestion and used a Button. Then your code you kindly wrote works.
the only trouble is, If a user has entered number(s) / Numeric values, And then presses the button, then the user realizes he has entered a wrong Value
in one or both textboxes. it is then I am stuck because the value of the Label ( LbNet ) has changed to the new total.

at first every time I clicked the button it just kept on adding to the total, So after clicking the button I disabled it.

Your code I have now with the alterations .

Private Sub CmdCalculate_Click(sender As Object, e As EventArgs) Handles CmdCalculate.Click
        Dim tot As Decimal = 0.00
        For Each c As Control In GroupBox4.Controls
            If c.GetType = GetType(TextBox) Then
                tot += GetDecimal(c.Text)
            End If
        Next
        Dim labVal As Decimal = GetDecimal(LbNet.Text.Replace("£"c, String.Empty))
        LbNet.Text = (labVal + tot).ToString("c2")
        ' or,  Label2.Text = (labVal + tot).ToString("c2")
    End Sub
    Function GetDecimal(s As String) As Decimal
        Dim v As Decimal = 0.00
        If Decimal.TryParse(s, v) Then Return v
        Return 0.00
    End Function

Regards
Gary

PS. would it help if I just used Textboxes instead of Labels?

Answer 4

Hi LesHay

Thanks again for taking the time and trouble to look at my question and writing out the code.

I tried your code altering your code to my Textboxes. ( I have exchange Labels for textboxes ) And the sum did not seem to change net value.
But I have written a simple code for the sum that works now.

Code I Have now.

Sub Calc()  
  
        Dim Sum1 As Decimal = GetDec(TxtSubTotal.Text)  
        Dim Sum2 As Decimal = GetDec(TxtVAT.Text)  
        Dim Sum3 As Decimal = GetDec(TxtWaitingTime.Text)  
        Dim Sum4 As Decimal = GetDec(TxtTolls.Text)  
  
        TxtNet.Text = Sum1 + Sum2 + Sum3 + Sum4  
        TxtNet.Text = FormatCurrency(TxtNet.Text)  
    End Sub  

    Private Sub TxtWaitingTime_TextChanged(sender As Object, e As EventArgs) Handles TxtWaitingTime.TextChanged, TxtTolls.TextChanged  
        Calc()  
    End Sub  
    Function GetDecimal(s As String) As Decimal  
        Dim v As Decimal = 0.0D  
        If Decimal.TryParse(s, v) Then Return v  
        Return 0.0D  
    End Function  
  
    Private Sub TxtWaitingTime_Leave(sender As Object, e As EventArgs) Handles TxtWaitingTime.Leave  
        If String.IsNullOrWhiteSpace(TxtWaitingTime.Text) = True Then  
            TxtWaitingTime.Text = "0.00"  
        ElseIf String.IsNullOrWhiteSpace(TxtWaitingTime.Text) = False Then  
            'do nothing just show value  
            TxtWaitingTime.Text = FormatCurrency(TxtWaitingTime.Text)  
        End If  
    End Sub  
  
    Private Sub TxtTolls_Leave(sender As Object, e As EventArgs) Handles TxtTolls.Leave  
        If String.IsNullOrWhiteSpace(TxtTolls.Text) = True Then  
            TxtTolls.Text = "0.00"  
        ElseIf String.IsNullOrWhiteSpace(TxtTolls.Text) = False Then  
            'do nothing just show value  
            TxtTolls.Text = FormatCurrency(TxtTolls.Text)  
        End If  
    End Sub  

Kindest Regards
Gary

When Data is selected

After entering value into textbox

after entering value into second textbox

Answer 5

Hi
Here is a slightly better version, doing away with the Leave event handler altogether. As usual with all the code I post, always needs proper testing and perhaps exception handling as the snippets I post are 'as is' and have limited testing and little or no exception handling.
This version seems to be OK as far as I have tested. and reduces the code somewhat.

Option Strict On
Option Explicit On
Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        TextBox1.Text = FormatCurrency(0)
        TextBox2.Text = FormatCurrency(0)
        TextBox3.Text = FormatCurrency(1.45)
        TextBox4.Text = FormatCurrency(2.55)
        TextBox5.Text = FormatCurrency(3.55)
        TextBox6.Text = FormatCurrency(4.45)
        Calc()
    End Sub
    Sub Calc()
        Dim tot As Decimal = 0.0D
        For Each gbc As Control In Controls
            If gbc.GetType = GetType(GroupBox) Then
                For Each c As Control In gbc.Controls
                    If c.GetType = GetType(TextBox) Then
                        tot += GetDecimal(c.Text.Replace("£"c, String.Empty))
                        AddHandler c.TextChanged, AddressOf TextBox_TextChanged
                    End If
                Next
            End If
        Next
        Label2.Text = FormatCurrency(tot)
    End Sub
    Private Sub TextBox_TextChanged(sender As Object, e As EventArgs)
        Dim c As TextBox = DirectCast(sender, TextBox)
        Dim pos As Integer = c.SelectionStart
        Dim len As Integer = c.SelectionLength
        c.Text = FormatCurrency(GetDecimal(c.Text.Replace("£"c, String.Empty)))
        c.SelectionStart = pos
        c.SelectionLength = len
        Calc()
    End Sub
    Function GetDecimal(s As String) As Decimal
        Dim v As Decimal = 0.0D
        If Decimal.TryParse(s, v) Then Return v
        Return 0.0D
    End Function
End Class