how to add combobox in rad grid using telerik controls?

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C#

C#4.0

Telerik

hi am new to telerik so am not able to add combobox inside radgrid so can any one suggest me??
here is my code please suggest me

<telerik:RadGrid ID="RadGrid1" AutoGenerateColumns="false" CellSpacing="0" GridLines="None"   runat="server">
        <ClientSettings>
        <Selecting CellSelectionMode="None" />
        </ClientSettings>
        <MasterTableView EditMode="InPlace" CommandItemDisplay="Top">
        <CommandItemSettings ExportToPdfText="Export to PDF" />
        <RowIndicatorColumn FilterControlAltText="Filter RowIndicator Column" Visible="true">
        <HeaderStyle Width="20px" />

        </RowIndicatorColumn>
        <ExpandCollapseColumn FilterControlAltText="Filter Expand Column" Visible="true">
        <HeaderStyle Width="20px" />

        </ExpandCollapseColumn>
        <Columns>
        <%--<telerik:GridBoundColumn UniqueName="Project" ReadOnly="true" HeaderText="Project">

        </telerik:GridBoundColumn> --%>
        <telerik:GridTemplateColumn UniqueName="TemplateColumn" HeaderText="Project">
        <EditItemTemplate>
        <telerik:RadComboBox ID="RadComboBox1" runat="server" Height="22px" Width="154px"></telerik:RadComboBox>
        </EditItemTemplate>
        </telerik:GridTemplateColumn>
        <telerik:GridTemplateColumn UniqueName="TemplateName1" HeaderText="Activity">
        <EditItemTemplate>
        <telerik:RadComboBox ID="RadComboBox2" runat="server" Height="22px" Width="154px"></telerik:RadComboBox>
        </EditItemTemplate>
        </telerik:GridTemplateColumn>
        <telerik:GridTemplateColumn UniqueName="TemplateName2" HeaderText="Tasks">
        <EditItemTemplate>
        <telerik:RadComboBox ID="RadComboBox3" runat="server" Height="22px" Width="154px"></telerik:RadComboBox>
        </EditItemTemplate>
        </telerik:GridTemplateColumn>
        </Columns>
        </MasterTableView>
        </telerik:RadGrid>

thank you