first use @Html.AntiForgeryToken() in html
$.ajax({
url: "@Url.Action("SomeMethod", "SomeController")",
type: 'POST',
data: JSON.stringify(jsonObject),
contentType: 'application/json; charset=utf-8',
dataType: 'json',
async: false,
beforeSend: function (request) {
request.setRequestHeader("RequestVerificationToken", $("[name='__RequestVerificationToken']").val());
},
success: function (msg) {
alert(msg);
}