Validate DropDownList and display error message in JavaScript Alert Box

Hi @compstuden

You have done syntax erros at many places.

Refer this code

HTML

 <div>
        <asp:DropDownList ID="ddlFinalAction" runat="server">
            <asp:ListItem></asp:ListItem>
            <asp:ListItem>A</asp:ListItem>
            <asp:ListItem>B</asp:ListItem>
            <asp:ListItem>C</asp:ListItem>
        </asp:DropDownList><br /><br />
        <asp:TextBox ID="TextBox5" runat="server"></asp:TextBox>
        <br />
        <br />
        <asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="return Validate()" />
    </div>

Javascript

<script type="text/javascript">
        function Validate() {
            if (document.getElementById('<%=ddlFinalAction.ClientID%>').selectedIndex == 0) {
                alert('Mus Enter Final Action Taken');
                return false;
            }

            if (document.getElementById('<%=ddlFinalAction.ClientID%>').selectedIndex == 1 || document.getElementById('<%=TextBox5.ClientID%>').value.length > 0) {
                alert('Must Enter Comment');
                return false;
            }
            return true;
        }
    </script>