I have following code to show multiple marker on gmap
Using Json.Net
var obj = new[] {
new object[] { "Bondi Beach", -33.890542, 151.274856, 4 },
new object[] { "Coogee Beach", -33.923036, 151.259052, 5 },
new object[] { "Cronulla Beach", -34.028249, 151.157507, 3 },
new object[] { "Manly Beach", -33.80010128657071, 151.28747820854187, 2 },
new object[] { "Maroubra Beach", -33.950198, 151.259302, 1 },
};
var json = JsonConvert.SerializeObject(obj);