Telerik:Radgrid selected keynames

The selected names of the Radgrid: ChangedList has to be shown in the Radgrid: Updatelist. that has to happen in one click on the button: ButtonALL_OnClick. What do I have to change to make it work?

RadGrid: ChangedList

     <telerik:RadGrid ID="ChangedList" AllowMultiRowSelection="True" runat="server" AutoGenerateColumns="false" OnPageIndexChanged="ChangedList_PageIndexChanged" OnNeedDataSource="ChangedList_NeedDataSource" GridLines="None" AllowPaging="true" RenderMode="Lightweight" PageSize="5" AllowSorting="True">

         <MasterTableView ClientDataKeyNames="Logging_ID, ModuleName, AssemblyVersion"  >

                <Columns> 


                    <telerik:GridClientSelectColumn  UniqueName="GridClientSelectColumn" >
                    </telerik:GridClientSelectColumn>   

                    <telerik:GridBoundColumn DataField="ModuleName" HeaderText="Naam"  UniqueName="ModuleName" ReadOnly="true">
                    </telerik:GridBoundColumn>

                    <telerik:GridBoundColumn DataField="AssemblyVersion" HeaderText="Versie" UniqueName="AssemblyVersion" ReadOnly="true">
                    </telerik:GridBoundColumn>


                  </Columns>
         </MasterTableView>

              <ClientSettings >

                  <Selecting AllowRowSelect="True" />

               </ClientSettings>

      </telerik:RadGrid>

Button: ButtonALL

              <br />       
            <div class="col-md-1" >
                <asp:Button ID="ButtonALL" runat="server"  Text="Update"  OnClick="ButtonALL_OnClick"   />
            </div>

RadGrid: Updatlist

    <telerik:RadGrid ID="Updatelist" AllowMultiRowSelection="True" runat="server" AutoGenerateColumns="true" OnPageIndexChanged="Updatelist_PageIndexChanged" OnNeedDataSource="Updatelist_NeedDataSource" GridLines="None" AllowPaging="true" RenderMode="Lightweight" PageSize="5" AllowSorting="True">

                 <MasterTableView ClientDataKeyNames="">

                     <Columns>

                     <telerik:GridClientSelectColumn UniqueName="GridClientSelectColumn">
                     </telerik:GridClientSelectColumn>

                     <telerik:GridBoundColumn DataField="" HeaderText=""  UniqueName="" ReadOnly="true">
                     </telerik:GridBoundColumn>

                     <telerik:GridBoundColumn DataField="" HeaderText="" UniqueName="" ReadOnly="true">
                     </telerik:GridBoundColumn>

                     </Columns>


                  </MasterTableView> 

                                <ClientSettings>

                                 <Selecting AllowRowSelect="True" />

                                 </ClientSettings>



             </telerik:RadGrid>

This is the CS code for the ButtonALL

 protected void ButtonALL_OnClick(object sender, EventArgs e)
    {

        ButtonALL.BackColor = System.Drawing.Color.PaleGreen;
        ButtonALL.BorderColor = System.Drawing.Color.Green;
        ButtonALL.ForeColor = System.Drawing.Color.Black;
        if (ButtonALL.Text == "Update")
        {

            ButtonALL.Text = "Updated";
        }
        else
        {

            ButtonALL.Text = "Update";
        }


        foreach (GridItem item in ChangedList.MasterTableView.Items)
        {
            GridDataItem dataitem = (GridDataItem)item;
            TableCell cell = dataitem["GridClientSelectColumn"];
            CheckBoxList checkBox = (CheckBoxList)cell.Controls[0];


            if (checkBoxList.Checked)
            {

                string value = dataitem.GetDataKeyValue("Logging_ID").ToString();
                string text = dataitem.GetDataKeyValue("ModuleName").ToString() + ", " + dataitem.GetDataKeyValue("AssemblyVersion").ToString();



            }


            DataTable dt = new DataTable();
            dt.Columns.Add("AssemblyVersion", typeof(string));
            dt.Columns.Add("ModuleName", typeof(int));


            DataRow dr = dt.NewRow();



            dr = dt.NewRow();

            dt.Rows.Add(dr);


            Updatelist.DataSource = dt;
            Updatelist.DataBind();


        }

        pnlNoItems.Visible = (Updatelist.Items.Count == 0);
        pnlTarget.Visible = !pnlNoItems.Visible;

}

(it was first A checkbox)