WebAPI/MVC - sending json list to server

Since you are sending a json which user enters using a form, you might consider using JObject class as your web api method parameter.

So in your form

<form id="form1">
    <input type="text" id="val1" name="val1" value="1" />
    <textarea class="form-control" id="json" name="json"></textarea>
    <button id="send">Send</button>
</form>

Now, on the button click,read the values of both the inputs and create a new object, and send that to the server.

$(function () {
    $("#send").click(function (e) {
        e.preventDefault();

        var v = $("#val1").val();
        var t = $("#json").val();
        var d = { val1: v, json: t };
        $.ajax({

            url: '/api/values',
            type: "POST",
            contentType: 'application/json',
            data: JSON.stringify(d),
            success: function (response) {
                console.log(response);
            },

            error: function (er) {
                console.log(er);
            }
        });

    });
});

And in the WebApi endpoint, you may use JObject as the parameter. The default model binder will be able to map the posted values to an object of JObject.

    public HttpResponseMessage Post([FromBody]JObject value)
    {
        var v = value["val1"];
        var j = value["json"];
        // do something with these 
        // v.Value will give you the value
        return Request.CreateResponse("Something received");
    }

JObject class belongs to Newtonsoft.Json.Linq namespace. So make sure to have a using statement to include that in your web api controller.