如何根据下拉/单选按钮验证文本框

Question

I am creating a page with optional drop down. If the user selects nothing, the text box is not required, if they do, it is. How do I do that?

(Optional drop down) -> Relative - Mother/Father/None

(Text box is required if user select 'Mother or Father')

Answer 1

对于上述答案，请不要忘记为下拉菜单分配AutoPostback = True属性，否则您将看不到效果。

Answer 2

You could disable your textbox by default.

Then when the user selects from the dropdown, enable the textbox.

As part of your validation you can check if the textbox is disabled, if it isn't then validate it.

The textbox becoming enabled can also act as a visual reference to the user that input is now required.

The don't really need to be related to each other as such.