Mvc Jquery Ajax Post returns null

Solution 1:

If you serializing the form, then you can add additional values to it with the .param() function

var data = $("#RentForm").serialize() + '&' + $.param({ 'aracid': AracID }, true);

$.ajax({
    type: "POST",
    url: '@Url.Action("Save","AracKirala")',
    data: data,
    ....

Solution 2:

MVC will map the object for you, so you might as well skip the extract nesting of the form within the object.

Notes:

• If aracid is also a property in the model, it will map to both the property and the extra parameter.
• Using push on the serialise() collection is more maintainable than the alternative of concatenating strings before the serialize() call.

e.g.

 var Kiralayan = $("#RentForm").serialize();            
 // Add the extra non-form parameter
 Kiralayan.push({name: 'aracid', value: P.AracID});

Full example:

    function Kaydet() {
        var Kiralayan = $("#RentForm").serialize();            
        // Add the extra non-form parameter
        Kiralayan.push({name: 'aracid', value: P.AracID});         
        console.log(params);

        $.ajax({
            type: "POST",
            url: '@Url.Action("Save","AracKirala")',
            data: Kiralayan,
            dataType: "text",
            success: function (response) {
                if (response != "OK") {
                    alert("Kayıt yapılamadı.");
                }
                else {
                    document.getElementById("RentForm").reset();
                    alert("Kayıt başarıyla gerçekleştirildi.");
                    $("#myModal").modal('hide');
                    Ara();
                }

            }
        });