How to call a 2 parameters js function from c# code behind ? (ASP.NET)

Question

I have a creating marker function is JS that I want to call from C# :

 function createMarker(position, information) {

        var marker = new google.maps.Marker({
            position: position,
            map: map

        });

        google.maps.event.addListener(marker, "click", function () {

            infowindow = new google.maps.InfoWindow({ content: information });
            if (prev_infowindow) {
                prev_infowindow.close();
            }

            prev_infowindow = infowindow;
            infowindow.open(map, this);


        });
        google.maps.event.addListener(map, "click", function () { //supprime l'infobulle affichée au clic sur la map

            infowindow.close();

        });
    }

At the beginning it only had 1 parameter and I was able to call it through c#, but now it has 2 parameters and I'm struggling to get it working. I always have a syntax error with ")" or ":".

  foreach (XmlElement elementNode in parentNode)
        {
            if (elementNode.GetAttribute("latitude") != String.Empty && elementNode.GetAttribute("longitude") != String.Empty)
            {
                lat = double.Parse(elementNode.GetAttribute("latitude"), CultureInfo.InvariantCulture)/100000;
                lng = double.Parse(elementNode.GetAttribute("longitude"), CultureInfo.InvariantCulture) / 100000;
                latStr = ""+lat;
                lngStr = ""+lng;
                latStr = latStr.Replace(',', '.');
                lngStr = lngStr.Replace(',', '.');



                position = "{lat: " + latStr + ", lng:" + lngStr + "}";

                if (DistanceTo(latitude, longitude, lat, lng) < distance)
                {
                    cpt++;
                    infoStations = "Some random string" ;
                    jsFunc = "createMarker(" + position + "," + infoStations+  ")";
                    coordMarkers.Add(new List<double> { lat, lng });

                    ScriptManager.RegisterClientScriptBlock(this, GetType(), "script"+cpt, "$(function () {" + jsFunc+"; });", true);
                }

            }

        }

Is it possible that the "," in the variable position is the problem ? Because if I only pass 1 parameter, it creates well the marker with an empty infoWindow, but with 2 parameters neither the markers or infowindow are showing.

Here is the working code :

 jsFunc = "createMarker(" + position + ")";
 ScriptManager.RegisterClientScriptBlock(this, GetType(), "script"+cpt, "$(function () {" + jsFunc+"; });", true);

Pass the variable in single quotes like this: <br><br> `jsFunc = "createMarker('" + position + "','" + infoStations+ "')"; It should work. — Sam
– Sam, Commented May 3, 2017 at 8:36
@Sam This method will fail when the string contains characters which need special handling to be used in a string literal. Writing code this way without escaping the string according to the rules (as for example HttpUtility.JavaScriptStringEncode does) does even make the site vulnerable to code injection and xss attacks. — NineBerry
– NineBerry, Commented May 3, 2017 at 8:41
Your solution is working too, however I can't pass position in single quotes otherwise it's not a LatLng variable. Thank you for your help ! — Alexandre
– Alexandre, Commented May 3, 2017 at 8:43
I would suggest to not "call" js from c#, but "enable" js from html. A marker div with all data attributes (lat, lng, whatever ...). Then in a separate js file, initialize a selector to start your logic. If the selector is empty it's not executed. BAM, no calling from c# required. — Tim Vermaelen
– Tim Vermaelen, Commented May 3, 2017 at 8:44
It seems interesting but I have no idea how to do it. I'll look it up later. Also I have been asked to do some c# code because it's easier to integrate so I'm trying to use some c# (otherwise I would have used only js :( ). — Alexandre
– Alexandre, Commented May 3, 2017 at 8:57

NineBerry · Accepted Answer · 2017-05-03 08:36:03Z

1

When passing a string as a parameter, you need to use the correct syntax for a JavaScript string literal, i.e. enclose it in double quotes.

Use the HttpUtility.JavaScriptStringEncode method to make a valid JavaScript string literal from a string in C#.

jsFunc = "createMarker(" + position + "," + HttpUtility.JavaScriptStringEncode(infoStations, true) +  ")";

answered May 3, 2017 at 8:36

NineBerry

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