extraxt data from sql server Base in a code javascript

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ASP.NET

Javascript

Google-Maps

Hello, I have a small project in asp.net / c # / javascript (to attack a google map)
on a asp.net page, I have a dropdownlist:

<asp:DropDownList ID="ddlAdr" runat="server" DataSourceID="SDSClient"
                                    DataTextField="Name_client" DataValueField="ID_client" >
</asp:DropDownList>
 
<div id="button2" class="button"  önclick="findAddress(); return false;">Chercher</div>
<asp:Button ID="btnsearch" Text="Search" runat="server" CssClass = "button" /> //c'est le meme boutton en haut

in the javascript code:

function findAddress() {
    var address = document.getElementById("ddlAdr").value;
 
    // script uses our 'geocoder' in order to find location by address name
    geocoder.geocode({ 'address': address }, function(results, status) {
        if (status == google.maps.GeocoderStatus.OK) { // and, if everything is ok
 
            // we will center map
            var addrLocation = results[0].geometry.location;
            map.setCenter(addrLocation);
 
            // store current coordinates into hidden variables
            document.getElementById('lat').value = results[0].geometry.location.$a;
            document.getElementById('lng').value = results[0].geometry.location.ab;
 
            // and then - add new custom marker
            var addrMarker = new google.maps.Marker({
                position: addrLocation,
                map: map,
                title: results[0].formatted_address
            });
        } else {
            alert('Geocode was not successful for the following reason: ' + status);
        }
    });
}

My problem is that the dropdown list displays the name of the client, but he as a ClientID value, I do not know how to extract the data for the selected element from a database and:
- Put a marker according to the extracted address
- View other data: name, surname, ... in a infowindow

I managed to create a marker but not retrieve data from a database sql server and pass a geocoder
I managed also to fill my dropdownlist from the BD