Jquery ajax call result cache problem

I am making an ajax call as follows setting cache: true. But even then aslo it does not store the ajax call result in the cache and everytime it makes ajax call for same 开发者_如何学编程thing.

$.ajax(
                            {
                                url: 'abc.aspx/getInfo',
                                cache: true,
                                type: 'POST',
                                data: '{userID: "' + id+ '"}', // id is a variabe
                                contentType: 'application/json; charset=utf-8',
                                dataType: 'json',
                                beforeSend: function() {
                                    // somthing...  
                                },
                               success: function(response, textStatus) {
                                 // something....
                               }
                             }

Can any one tell me why it is happening. How to solve this?

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IIRC cache works with GET requests. For POST requests you need to have your server side script send proper HTTP cache headers.