Display Google maps from database on button click in ASP.Net

hello I have a problem with displaying maps in page load the map is displayed, but when I want to execute the code on a button click the map is not displayed

Function javascript

function AfficherMap() {
    //     alert("ssss");
    var mapOptions = {
        center: new google.maps.LatLng(markers[0].lat, markers[0].lng),
        zoom: 10,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    var map = new google.maps.Map(document.getElementById("map-canvas"), mapOptions);
    var infoWindow = new google.maps.InfoWindow();
    var lat_lng = new Array();
    var latlngbounds = new google.maps.LatLngBounds();
    for (i = 0; i < markers.length; i++) {
        var data = markers[i]
        var myLatlng = new google.maps.LatLng(data.lat, data.lng);
        lat_lng.push(myLatlng);

        var marker = new google.maps.Marker({
            position: myLatlng,
            map: map,
            title: data.title
        });
        latlngbounds.extend(marker.position);
        (function (marker, data) {
            google.maps.event.addListener(marker, "click", function (e) {
                infoWindow.setContent(data.description);
                infoWindow.open(map, marker);
            });
        })(marker, data);
    }
    map.setCenter(latlngbounds.getCenter());
    map.fitBounds(latlngbounds);
    /////////////////////////////////////////77777

    var service = new google.maps.DirectionsService();
    var directionsDisplay = new google.maps.DirectionsRenderer();
    directionsDisplay.setMap(map);

    var waypts = [];
    for (j = 1; j < lat_lng.length - 1; j++) {
        waypts.push({ location: lat_lng[j],
            stopover: true
        });
    }

    var request = {
        origin: lat_lng[0],
        destination: lat_lng[lat_lng.length - 1],
        waypoints: waypts,
        travelMode: google.maps.DirectionsTravelMode.DRIVING
    };
    service.route(request, function (result, status) {
        if (status == google.maps.DirectionsStatus.OK) {
            directionsDisplay.setDirections(result);
        } else { alert("Directions request failed:" + status); }
    });
}

button Click 

protected void Button3_Click(object sender, EventArgs e)
{
    string s = "2014-11-05";
    LocalisationVenteDao.ds.Reset();
    LocalisationVenteDao.Instance.LocalisationVenteToDB(Sql.Instance.GetSqlConnection(), s);
    rptMarkers.DataSource = LocalisationVenteDao.ds.Tables[0];
    GridView1.DataSource = LocalisationVenteDao.ds.Tables[0];
    rptMarkers.DataBind();
    GridView1.DataBind();
    ClientScript.RegisterStartupScript(this.GetType(), "blablaosef", "<script type='text/javascript'>AfficherMap();</script>");
}