主题：ValueChanged

要判断一下值是不是空值

Dim rkqssj As WinForm.DateTimePicker = e.Form.Controls("DateTimePicker1")

Dim rkjzsj As WinForm.DateTimePicker = e.Form.Controls("DateTimePicker2")

Dim tjrkzq As WinForm.TextBox = e.Form.Controls("TextBox1")

If rkqssj.Value = Nothing Then
    msgbox("d1为空")
    Return
End If
If rkjzsj.Value = Nothing Then
    msgbox("d2为空")
    Return
End If

Dim t1 As TimeSpan  = rkjzsj.value.AddDays(1) - rkqssj.Value

tjrkzq.text = "入库周期共计:" & t1.days & "天"