Converting from lbl.Text to currecy

Question

In the Case statement below, I am getting an error when trying to convert the results on lblTotal.Text to Currency. Any tips and suggestions would be helpful.

Case strCalculus
lblSubtotal.Text -= decCalculus
lblTax.Text -= decCalculus * decTAX_RATE
lblTotal.Text = lblSubtotal.Text + lblTax.Text + lblShipping.Text
lblShipping.Text -= dblShippingCharge
Case strHistoryScotland
lblSubtotal.Text -= decHistoryScotland
lblTax.Text -= decHistoryScotland * decTAX_RATE
lblTotal.Text = lblSubtotal.Text + lblTax.Text + lblShipping.Text

            lblShipping.Text -= dblShippingCharge

    End Select
    lblTotal.Text = CDbl(lblTotal.Text).ToString("c")

Answer 1

Most probably the following line caused the value of lblTotal.Text not a proper number.

lblTotal.Text = lblSubtotal.Text + lblTax.Text + lblShipping.Text

Try use the following instead:

lblTotal.Text = CStr(CDbl(lblSubtotal.Text) + CDbl(lblTax.Text) + CDbl(lblShipping.Text))

Answer 2

This will work

Dim value As Double = 0
If Double.TryParse(lblTotal.Text, value) Then
    lblTotal.Text = $"{value.ToString("c")}"
Else
    lblTotal.Text = "Invalid value"
End If

Or create a currency label

Public Class CurrencyLabel
    Inherits Label
    Public ReadOnly Property AsCurrent() As String
        Get
            Dim value As Double = 0
            If Double.TryParse(Text, value) Then
                Text = $"{value.ToString("c")}"
            End If

            Return Text

        End Get
    End Property
End Class