See in following way
$.ajax({
url: "WebService.cs/downloadSelectedSongs",
dataType: "json",
type: "POST",
data: {songs: ['true', 'false', 'false'] },
contentType: "application/json; charset=utf-8",
error: function () {
alert("errrrror");
},
success: function (data) {
alert(data.d);
}
});
In webmethod should be
[WebMethod]
public static string downloadSelectedSongs(bool[] songs)
{
return "ok";
}