how to validating unique entries of textbox on repeater control? - asp.net

Question

I have a repeater control rptbrand in which one textbox txtMultiBrand is there and after each repeating time when i click btnAddBrand button i want validation for unique entries in textbox, here is my aspx code
<table width="100%">
<asp:Repeater ID="rptBrand" runat="server" OnItemDataBound="rptBrandDetail_ItemDataBound">
<ItemTemplate>
<tr>
<td align="right" `enter code here`width="150">
Brand<asp:Label ID="lblBrandNum" runat="server"></asp:Label>
<span class="msgred">*</span> :
</td>
<td align="left">
<table width="100%">
<tr>
<td align="left" width="20%">
<asp:TextBox ID="txtMultiBrand" CssClass="imageSearch" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator14" runat="server" ValidationGroup="VGrpMultiSave"
ControlToValidate="txtMultiBrand" ErrorMessage="Brand Required" Display="none"
SetFocusOnError="True"></asp:RequiredFieldValidator>
<asp:RequiredFieldValidator ID="RequiredFieldValidator11" runat="server" ValidationGroup="VGrpSave"
ControlToValidate="txtMultiBrand" ErrorMessage="Brand Required" Display="none"
SetFocusOnError="True"></asp:RequiredFieldValidator>
</td>
<td align="left">
<asp:ImageButton ID="btnDelete" runat="server" CausesValidation="false" CommandName="CmdDelete"
CommandArgument='<%# Eval("SrNo") %>' ToolTip="Delete" ImageUrl="images/b_drop.png"
OnCommand="rptBrand_Command" Width="16" Height="16" OnClientClick="javascript:return confirm('Are you sure you want to remove brand?')" />
</td>
</tr>
</table>
</td>
</tr>
</ItemTemplate>
</asp:Repeater>
<tr>
<td align="right" width="150">
</td>
<td>
<asp:Button ID="btnAddBrand" runat="server" Text="Add more" ValidationGroup="VGrpMultiSave"
OnClick="btnAddBrand_Click" />
<asp:ValidationSummary ID="ValidationSummary2" runat="server" DisplayMode="List"
ShowMessageBox="True" ShowSummary="False" ValidationGroup="VGrpMultiSave" />
</td>
</tr>
</table>

Answer 1

Using jQuery:
IT IS WORKING
Check the below link:
http://jsfiddle.net/NtF7h/
$(function () {
$("#<%=btnAddBrand.ClientID%>").on("click", function (event) {
var valueArray = new Array(); ;
$("input[id*='txtMultiBrand']").each(function (index) {
if ($.inArray($(this).val(), valueArray) == -1) {
valueArray[index] = $(this).val();
}
else {
alert("Duplicate Entry Found.");
event.preventDefault();
return false;
}
});
});
});