如何将字符串从视图传递到 mvc 中的控制器

Question

This JavaScript code is being used to pass a string from a view to an action in a controller:

<script type="text/javascript">
    $(document).on('click', 'a', function () {
        $.ajax({
            type: 'POST',
            url: '/brandsOfACategory',
            contentType: 'application/json; charset:utf-8',
            data: JSON.stringify(this.id)
        })
    });
</script>

brandsOfACategory code in the controller:

public ActionResult brandsOfACategory(string id)
    {
        return View();
    }

Code is not working as expected as id is coming as null.

Can someone please guide?

Answer 1

$.ajax({
  type: 'POST',
  url: '/brandsOfACategory',
  contentType: 'application/json; charset:utf-8',
  data: { 'id': id }
})

Answer 2

Ajax Code

$.ajax({
    url: "controllerurl",
    type: "POST",
    data: {
        id: "123"
    },
    dataType: "json",
    success: function(result) {
        //Write your code here
    }
});

For more info about ajax link

Parameter binding in ASP.Net link

Answer 3

With your current code, when the ajax call is made, the request payload has only a string value. For example, if your clicked link has an Id attribute value "link1", it will send the below string as the request payload for your ajax call.(You can see this if you open up your dev tools->network tab)

"link1"

For model binding to work, the payload should have a key-value format so that the value will be mapped to the parameter with the same value as the key.

Since it is a simple value, you do not need to necessarily send the JSON stringified version and the contentType as application/json . Simply send the JS object as data . Make sure you are sending a JavaScript object which has the key/property name same as your action method parameter name( id ) and it will work.

Assuming your anchor tag has a valid Id attribute value so that the this.id expression returns the valid string value.

<a href="/SomeUrl" id="myId">MyLink</a>

In the script, you probably want to stop the normal click behavior as well to prevent the page from navigating to the href attribute value.

$(document).on('click', 'a', function (e) {
    e.preventDefault();

    $.ajax({
        type: 'POST',
        url: '/brandsOfACategory',
        data: { id :this.id } 
    }).done(function (res) {
        console.log('result from ajax call',res);
    })
});

This will send the value like id=myId as the Form Data for the request. Since you are not specifying the contentType explicitly, it will use the default application/x-www-form-urlencoded

If the link user clicked does not have an Id attribute, the code will send no value because this.id will return an empty string and your parameter value at server side will be null.