Server Error in '/' Application.

---

<telerik:RadComboBox ID="ddlSpecialty" runat="server" AutoPostBack="true" AppendDataBoundItems="true" EnableEmbeddedSkins="false" Skin="Activity" Width="185px" Height="300px" emptyMessage="Click to change Specialties" >

<ItemTemplate>

<asp:CheckBox ID="chkSpecialty" runat="server" RepeatDirection="Horizontal" RepeatLayout="Flow" AutoPostBack="true"></asp:CheckBox>

<asp:Label ID="lblSpecialty" runat="server" AssociatedControlID="chkSpecialty"><%#Eval("Specialty") %></asp:Label>

</ItemTemplate>

</telerik:RadComboBox>

Hello I want to filter column in my grid with filtertempalte column including RadComboBox
the code look like this(i have already read the blogs and have seen the demos about filter template)

<telerik:GridTemplateColumn DataField="Obraz" Visible="false" Resizable="false" UniqueName="TemplateColumn"

AllowFiltering="true">

<FilterTemplate>

<telerik:RadComboBox ID="ComboFilterBox" runat="server" AppendDataBoundItems="true" OnSelectedIndexChanged="FilterCombo_SelectedIndexChanged" DataTextField="Obraz" DataValueField="Obraz"

OnLoad="Combo_NeedDataSource" AutoPostBack="true">

<items>

<telerik:RadComboBoxItem />

</items>

</telerik:RadComboBox>

</FilterTemplate>

<ItemTemplate>

<asp:Image ID="Image1" runat="server" ImageUrl="<%# bind('Obraz') %>" ForeColor="White" />

</ItemTemplate>

<HeaderStyle Width="170" />

<ItemStyle Width="170px" />

</telerik:GridTemplateColumn>

and then in Code-Behind I have placed the function

protected

void FilterCombo_SelectedIndexChanged(object o, RadComboBoxSelectedIndexChangedEventArgs e)

{

string filterExpression;

filterExpression =

"([Obraz] = '" + e.Value + "')";

RadGrid1.MasterTableView.FilterExpression = filterExpression;

RadGrid1.MasterTableView.Rebind();

}

and then when I change the values in combobox i get the error
 Sys.WebForms.PageRequestManagerServerErrorException: Expression expected
after Rebind.
Please help.