主题：关于时间类型的判空

Dim txt As Date = e.Sender.Text
If txt <> Nothing  Then
      Dim d As Date = e.Form.Controls("partyTime").Value
      Dim y As Integer = d.year
      If format(d, "MMdd") <= Format(Date.Today, "MMdd") Then
           y = Date.Today.Year - y-1
      Else
           y = 0
      End If
      If y < 0 Then
             e.Form.Controls("partyStanding").Value = 0
      Else
             e.Form.Controls("partyStanding").Value = y
      End If
End If

老是，红色部分由问题么？从字符串“”到类型“Date”的转换无效。

Dim txt As Date = e.Sender.Text
If txt <> Nothing  Then

改成

Dim txt As String = e.Sender.Text
If txt <> Nothing Then