程序崩溃 Visual Basic答案

【问题标题】：Program crashing Visual Basic程序崩溃 Visual Basic
【发布时间】：2015-06-02 18:43:12
【问题描述】：

我正在使用 Visual Basic 进行编程，并且我创建了一个贷款计算器程序。我几乎所有的东西都是正确的，它也几乎按照我想要的方式工作和运行。

到目前为止，这是我的代码：

公开课表1

Private MinAmt As Decimal = 1000
Private MaxAmt As Decimal = 200000
Private Drate As Decimal
Private Loan As Decimal

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    '== Load the Rate and Terms combo, then 'click Reset
    For r As Decimal = 0 To 0.1475 Step 0.0025
        '== Add each successive value to the combo list
        cbxRate.Items.Add(Format(r, "00.00%"))
    Next
    For t As Byte = 12 To 120 Step 6
        cbxTerm.Items.Add(Format(t, "00"))
    Next
    btnReset.PerformClick()
End Sub

Private Sub btnReset_Click(sender As Object, e As EventArgs) Handles btnReset.Click
    '== Set the defaults, and clear my prior answers
    cbxRate.Text = "06.00%"
    cbxTerm.Text = "36"
    tbxLoan.Text = "10,000"
    lblPayment.Text = ""
End Sub

Private Sub btnCalc_Click(sender As Object, e As EventArgs) Handles btnCalc.Click
    '== Validate the loan amount (number 1,000 - 200,000);

    If IsNumeric(tbxLoan.Text) AndAlso tbxLoan.Text >= MinAmt AndAlso tbxLoan.Text <= MaxAmt Then
        Loan = tbxLoan.Text
    Else
        MessageBox.Show("Error invalid value")
        tbxLoan.Focus()
        tbxLoan.SelectAll()
    End If

    '== Calculate Monthly Payment as PMT(monthly decimal rate, term in months, minus amount)
    lblPayment.Text = Pmt(cbxRate.Text.Replace("%", "") / 1200, cbxTerm.Text, -tbxLoan.Text)

    '== Display formatted as money: FormatCurrency(blah blah blah)
    lblPayment.Text = FormatCurrency(lblPayment.Text, 2)
End Sub

Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
    Close()

End Sub

Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
    '== Confirm he means it, else cancel attempt to close.
    If MessageBox.Show("Do you really want to exit?", "Close", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Yes Then
    Else
        e.Cancel = True
    End If
End Sub

结束类

我试图发布我的程序的图片以便更容易，但显然我没有足够的声望点，但我会尽力解释。

我想消除有人不小心将字母作为值放入“输入贷款金额”空间的问题。现在，如果我在“输入贷款金额”空间中输入一个字母“U”，它会弹出一个错误（这是我想要的），但它也会使程序崩溃（我不想要的）。

希望这是有道理的。有人能指出我正确的方向吗？我还是 Visual Basic 的新手。

谢谢！

【问题讨论】：

标签： vb.net vb6 basic

【解决方案1】：

这是因为您要继续计算输入是否有效。

输入无效后使用Return退出函数。

Else
    MessageBox.Show("Error invalid value")
    tbxLoan.Focus()
    tbxLoan.SelectAll()
    Return
End If

【讨论】：

非常感谢，工作就像一个魅力。我应该看到一个愚蠢的简单错误。无论如何谢谢你
@LukeMcSloy，没问题.. 随时接受答案 + 点赞。

【解决方案2】：

或者只是将计算移到 If 语句中

Private Sub btnCalc_Click(sender As Object, e As EventArgs) Handles btnCalc.Click

    '== Validate the loan amount (number 1,000 - 200,000);
    If IsNumeric(tbxLoan.Text) AndAlso tbxLoan.Text >= MinAmt AndAlso tbxLoan.Text <= MaxAmt Then

        Loan = tbxLoan.Text

        '== Calculate Monthly Payment as PMT(monthly decimal rate, term in months, minus amount)

        lblPayment.Text = Pmt(cbxRate.Text.Replace("%", "") / 1200, cbxTerm.Text, -tbxLoan.Text)

        '== Display formatted as money: FormatCurrency(blah blah blah)
        lblPayment.Text = FormatCurrency(lblPayment.Text, 2)

    Else
        MessageBox.Show("Error invalid value")
        tbxLoan.Focus()
        tbxLoan.SelectAll()
    End If

End Sub

【讨论】：

【解决方案3】：

您仍在执行其余代码。您需要退出该块。使用 Return 语句..

Else
    MessageBox.Show("Error invalid value")
    tbxLoan.Focus()
    tbxLoan.SelectAll()
    Return
End If

【讨论】：