Introduction
In asp.net there are some situations when a web
developer needs to validate ListBox and DropDownList using Required Field
Validator. It seems to be little bit tricky and also it avoids the use of
JavaScript function to validate ListBox and DropDownList .
I am sharing the code which will help the Developers:
First for ListBox
<asp:ListBox ID="lstboxStudent" runat="server" Width="200px" SelectionMode="Multiple">
<asp:ListItem Value="1">Shrish</asp:ListItem>
<asp:ListItem Value="2">Saurabh</asp:ListItem>
<asp:ListItem Value="3">Seema</asp:ListItem>
<asp:ListItem Value="4">Maanas</asp:ListItem>
</asp:ListBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1"ControlToValidate="lstboxStudent" InitialValue="" runat="server" ErrorMessage="Please select atleast
one Student"></asp:RequiredFieldValidator>
And Now, For
DropDownList
<asp:DropDownList ID="ourCity" runat="server" Width="200px">
<asp:ListItem Value="0">--Select--</asp:ListItem>
<asp:ListItem Value="1">Capetown</asp:ListItem>
<asp:ListItem Value="2">NewYork</asp:ListItem>
<asp:ListItem Value="3">Sydeny</asp:ListItem>
<asp:ListItem Value="4">Mumbai</asp:ListItem>
</asp:DropDownList> <asp:RequiredFieldValidator ID="RequiredFieldValidator2" ControlToValidate="ourCity" InitialValue="0" runat="server" ErrorMessage="Please select
city"></asp:RequiredFieldValidator>