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How To Use A RequiredFieldValidator With A DropDownList

I love the ASP.NET validation controls. There are times however when you need to know the ins-and-outs to use them successfully. For example, what do you do when you want to require an option to be selected from a DropDownList on the client side?

If you simply add a RequiredFieldValidator, set the right ValidationGroup and set the validator’s ControlToValidate property, when you submit the form the field will not be validated because you are missing a key piece of the puzzle. You need to set the validator’s InitialValue property for things to work.

Here is a working example:

<asp:DropDownList   runat="server" ID="DropDownList1">
	<asp:ListItem Value="0">Please select</asp:ListItem>
	<asp:ListItem Value="1">Option 1</asp:ListItem>
	<asp:ListItem Value="2">Option 2</asp:ListItem>
</asp:DropDownList>
<asp:RequiredFieldValidator runat="server" ControlToValidate="DropDownList1" InitialValue="0"></asp:RequiredFieldValidator>

By setting the validator’s InitialValue to 0, we make sure that if nothing is selected from the DropDownList ie if value 0 is submitted, the validator marks the DropDownList control as invalid.

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