$.post vs $.ajax

It doesn't work because in your $.post method you cannot set the content type of the request to application/json. So it is not possible to invoke an ASP.NET PageMethod using $.post because an ASP.NET PageMethod requires a JSON request. You will have to use $.ajax.

I would just modify the data in order to ensure that it is properly JSON encoded:

$.ajax({    type: "POST",    url: "StandardBag.aspx/RemoveProductFromStandardBag",    data: JSON.stringify({ standardBagProductId: standardBagProductId.trim() }),    success: function() {        $(".reload").click();    },    dataType: "json",    contentType: "application/json"});

This is another way to do it not using ajax. It uses post and returns a json object.

data = {};data.standardBagProductId = standardBagProductId.trim();$.post("StandardBag.aspx/RemoveProductFromStandardBag", data , function(response){    $(".reload").click();},"json");

for $.post function second param should not be in "".

$.post("StandardBag.aspx/RemoveProductFromStandardBag",    {'standardBagProductId': standardBagProductId.trim() },    function () { $(".reload").click(); },    "json");