Untitled

<%@ Page Language="C#" AutoEventWireup="true" EnableEventValidation="false" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <title></title>
    <script runat="server">
        public IEnumerable<int> Measurements_GetData()
        {
            return new[] { 123, 328, 1099 };
        }
    </script>
</head>
<body>
    <form method="post" runat="server">
        <asp:ScriptManager runat="server" />
        <asp:UpdatePanel runat="server">
            <ContentTemplate>
                <h1>OK</h1>
                <div>
                    <asp:TextBox ID="Measurement1" runat="server" Text="123" AutoPostBack="true"  />
                </div>

                <div>
                    <asp:TextBox ID="TextBox1" runat="server" Text="328" AutoPostBack="true" />
                </div>

                <div>
                    <asp:TextBox ID="TextBox2" runat="server" Text="1099" AutoPostBack="true" />
                </div>

                <h1>Not OK</h1>
                <asp:Repeater ID="Measurements" runat="server" SelectMethod="Measurements_GetData" ItemType="System.Int32">
                    <ItemTemplate>
                    <div>
                        <asp:TextBox ID="Measurement" runat="server" AutoPostBack="true" Text="<%# Item %>" />
                    </div>
                    </ItemTemplate>
                </asp:Repeater>
            </ContentTemplate>
        </asp:UpdatePanel>
    </form>
    <script type="text/javascript">
        (function () {
            var focusedElementId = "";
            var prm = Sys.WebForms.PageRequestManager.getInstance();

            prm.add_pageLoaded(function (source, args) {
                // re-focus element, if any selected prior to postback
                if (focusedElementId !== "") {
                    document.getElementById(focusedElementId).focus();
                    console.log("focus:" + focusedElementId);
                }
            });

            prm.add_pageLoading(function (source, args) {
                var fe = document.activeElement;
                focusedElementId = fe !== null ? fe.id : "";
            });
        })();
    </script>
</body>
</html>