How can I send a JSON POST when the string contains HTML tags

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C#

Ajax

MVC

JSON

I know that the variable 'LastSelectedSettingValue' will sometimes contain html tags.
When it is simple text the JSON below works fine. When it contains HTML the JSON below fails. I have tried JSON.Encode() and other things, but without success.

$.ajax({
               url: '/StoreAdmin01/UpdateSetting',
               type: 'POST',
               dataType: "json",
               traditional: true,
               async: false,
               data: { settingId: LastSelectedSettingIdValue, settingValue: LastSelectedSettingValue, time: new Date() },
               success: function (result) {
               },

               error: function () {
                   alert("error");

               }
           });