如何累積用戶輸入的值？

Question

我完全停留在這個課堂上。我有一個計算銷售稅和百分比的程序..但我需要有3個累積文本框;即當用戶輸入他們的小計時，它會保存到一個變量中，然後當他們下一次輸入時，它會將它添加到同一個變量並顯示它。 我一直在這小時並沒有運氣，並不斷收到錯誤。

Dim numberOfInvoices As Integer 
Dim totalOfInvoices As Decimal 
Dim invoiceAverage As Decimal 

Private Sub btnCalculate_Click(sender As Object, e As EventArgs) Handles btnCalculate.Click 
    Dim subtotal As Decimal = CDec(txtEnterSubtotal.Text) 
    Dim discountPercent As Decimal = 0.25D 
    Dim discountAmount As Decimal = Math.Round(subtotal * discountPercent, 2) 
    Dim invoiceTotal As Decimal = subtotal - discountAmount 
    Dim accumSubtotal As Decimal = subtotal 

    txtSubtotal.Text = FormatCurrency(subtotal) 
    txtDiscountPercent.Text = FormatPercent(discountPercent, 1) 
    txtDiscountAmount.Text = FormatCurrency(discountAmount) 
    txtTotal.Text = FormatCurrency(invoiceTotal) 

    numberOfInvoices += 1 
    totalOfInvoices += invoiceTotal 
    invoiceAverage = totalOfInvoices/numberOfInvoices 

    Me.txtNumberOfInvoices.Text = numberOfInvoices.ToString 
    Me.txtTotalOfInvoices.Text = FormatCurrency(totalOfInvoices) 
    Me.txtInvoiceAverage.Text = FormatCurrency(invoiceAverage) 


    '-------This is where i've been trying to accumulate values------' 
    'I need to accumulate the subtotal everytime the user enters something 
    'txtAccumSubtotal.text = 'the variable that adds evertime a new number is input into txtEnterSubtotal.text 

    txtEnterSubtotal.Text = "" 
    txtEnterSubtotal.Select() 
    'This is a comment 
End Sub 

希望我在代碼中解釋了這個權利。我真的需要幫助。

Answer 1

每次點擊時，都會將當前SubTotal分配給AccumSubTotal。在Click事件外聲明Accum Sub，然後將新的SubTotal添加到它。

試試看......我會顯示代碼，但你想學習，不是嗎？提示：

AccumSubTotal += subtotal 

或老同學

AccumSubTotal = AccumSubTotal + subtotal