How to Divide Two Textbox Values

[jttrinh]

Hi, I'm having problems trying to figure out how to divide the value in a text box.

One textbox is named Purchase Price
I want to take that number and get it divided by 5. That answer will be the down payment.
I declared a const for downpayment for 5.
I did the ToDouble for the purchase price as well for downpayment. I'll put what I have down so far for the coding. I'm just having trouble finding my error.

Imports System.Convert
Public Class Form1
    Private Const DOWN_PAYMENT As Double = 5
    Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click
        Me.Close()
    End Sub

    Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
        txtPurchasePrice.Text = ""
        txtInterestRate.Text = ""
        txtDownPayment.Text = ""
    End Sub

    Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
        Dim PurchasePrice As Double
        Dim InterestRate As Double
        Dim DownPayment As Double

        PurchasePrice = ToDouble(txtPurchasePrice.Text)

        InterestRate = ToDouble(txtInterestRate.Text) / 100

        DownPayment = ToDouble(txtDownPayment.Text)
        DownPayment = txtPurchasePrice.Text / 5
        DownPayment = System.Math.Abs(DownPayment)


    End Sub
End Class

If anyone could help me out please.

[jttrinh]

I thought adding

DownPayment = txtDownPayment.ToString("C")

Would help out to imported the value, but it gives me an error message of:

Value of type 'Char' cannnot be converted to 'Double'

I'm exactly sure what that means...

[Reverend Jim]

The following three statements get the values correctly

Dim PurchasePrice As Double = ToDouble(txtPurchasePrice.Text)
Dim InterestRate As Double = ToDouble(txtInterestRate.Text) / 100
Dim DownPayment As Double = ToDouble(txtDownPayment.Text)

However, if you are calculating the minimum down payment as a portion of the purchase price then there is no reason for the third line unless you intend to do something like

Dim PurchasePrice As Double = ToDouble(txtPurchasePrice.Text)
Dim InterestRate As Double = ToDouble(txtInterestRate.Text) / 100
Dim DownPayment As Double = ToDouble(txtDownPayment.Text)
Dim MinimumDown As Double = PurchasePrice / DOWN_PAYMENT

If DownPayment < MinimiumDown Then
    MsgBox("The minimum down payment is " & MinimumDown)
    etc.

And keep in mind that you should validate the text controls before converting to ensure that they are valid. That means

• checking that the entered values are numeric
• checking that the entered values are within a given range of allowable values

[jttrinh]

Thanks Jim, a comment to your last statement when you say the make sure the value are numeric is the statement.

"If IsNumeic(txtPurchasePrice.Text) Then"

[Reverend Jim]

That will do it.