IHttpActionResult生成xml解析器错误

Question

这是整个交易和控制的希望，这将提供更多解决方案

IHttpActionResult在更新数据时生成xml解析器错误

    [ResponseType(typeof(void))]
    public IHttpActionResult Postzl_volunteer(int id, zl_volunteer zl_volunteer)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        if (id != zl_volunteer.id_volunteer)
        {
            return BadRequest();
        }

        db.Entry(zl_volunteer).State = EntityState.Modified;

        try
        {
            db.SaveChanges();
        }
        catch (DbUpdateConcurrencyException)
        {
            if (!zl_volunteerExists(id))
            {
                return NotFound();
            }
            else
            {
                throw;
            }
        }

所有api工作正常，未更新表行（api）。错误：XML解析器错误

<script type="text/javascript">
    $('#updatecustomer').click(function (data) {
        var idcustomer = $('#editid').val();
        var firstnamen = $("#firstname").val();
        var midnamen = $("#midname").val();
        var lastnamen = $("#lastname").val();
        var fullnamen = $("#fullname").val();
        var custphone = $("#customphone").val();
        var volmail = $("#volmail").val();
        var postcodes = $("#custompostal").val();
        var streetnr = $("#customhnum").val();
        var customstreets = $("#customstreet").val();
        var customplace = $("#tcplace").val();
        var datatest = $("#test").val();
            $.ajax({
                url: '/api/zl_volunteer/34',
                cache: true,
                dataType: 'json',
                type: "post",
                data: {
                    firstname: firstnamen, midname: midnamen, lastname: lastnamen,
                    full_name: fullnamen, postcode: postcodes, email: volmail, phone_mob: custphone,
                    adr_number: streetnr, adress: customstreets, place: customplace, gender: datatest, age: datatest, phone: datatest, comment: datatest
                },
                success: function (data) {
                    $(data).each(function (i, item) {
                        $(item).each(function (i, nwid) {
                            console.log('Nieuw ID ' + nwid.full_name);
                            $("#editscid").val(nwid.id_training);

                        });
                    });
                },
                error: function (request, status, error) {
                    console.log('error', error)
                },
                complete: function () {
                    console.log('Succesvol Opgeslagen');
                    $("#saving").css("display", "none");
                    $("#editmode").val(1);
                    setTimeout(function () {

                    }, 3000);
                }
            });


    });
</script>

输出在控制台中给出： XML解析错误：找不到主要元素位置：http://localhost:63084/api/zl_volunteer/34 行号1，行1：