蒙面文本框导致 VB.NET 中出现错误

Question

在我的代码中使用 maskedtextbox 时，returns 出现异常：

Conversion from string "" to type 'Date' is not valid

我的代码是：

Dim msg, first, second As String
Dim firstdate, seconddate As Date
first = MaskedTextBox1.Text
second = MaskedTextBox2.Text
firstdate = CDate(first)
seconddate = CDate(second)
msg = "Days from today: " & DateDiff(DateInterval.Month, firstdate, seconddate)
MsgBox(msg)

但是如果使用文本框代替掩码文本框，我的代码可以正常工作，例如：

Dim msg, first, second As String
Dim firstdate, seconddate As Date
first = TextBox3.Text
second = TextBox4.Text
firstdate = CDate(first)
seconddate = CDate(second)
msg = "Days from today: " & DateDiff(DateInterval.Month, firstdate, seconddate)
MsgBox(msg)

Answer 1

最好使用其中一种解析方法来验证日期信息：

If DateTime.TryParse(first, firstdate) AndAlso _
   DateTime.TryParse(second, seconddate) Then
  msg = "Days from today: " & DateDiff(DateInterval.Day, firstdate, seconddate)
  MessageBox.Show(msg)
Else
  MessageBox.Show("Invalid dates entered.")
End If

蒙面文本框导致 VB.NET 中出现错误

Masked textbox causing error in VB.NET

vb.net

textbox

maskedtextbox