C# MVC 4 Call Void using Javascript in Controller

Question

I am completely new in MVC4 studying for a few weeks, I am asking how to call a Public Void from View to Controller and what is the best procedure to call? using JavaScript? or Html.Action ?

Here is my Code in Action Controller:

[HttpPost]
[AcceptVerbs(HttpVerbs.Post)]
public static string SearchAd(string LoginName = "")
{
    string x = "Not Found";
    DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://lbcone");
    DirectorySearcher directorySearcher = new DirectorySearcher(directoryEntry);
    directorySearcher.Filter = string.Format("(&(SAMAccountName={0}))", LoginName);
    var user = directorySearcher.FindOne();
    if (user != null)
    {
        x = "Found";
    }
    return x;
}

Here is my Code in Javascript it has an error:

<script type='text/javascript'>
    function SetValue(ctl, event) {
        event.preventDefault();
        var LoginName = document.getElementById('_LoginName').value;
        var x = SearchAd(LoginName);
        alert(x);
    }
</script>

Here is my View button:

button type="button" onclick="SetValue();">

Answer 1

In this way will work fine :

[HttpPost]
[AcceptVerbs(HttpVerbs.Post)]
public static ActionResult SearchAd(string LoginName = "")
{
    string x = "Not Found";
    DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://lbcone");
    DirectorySearcher directorySearcher = new DirectorySearcher(directoryEntry);
    directorySearcher.Filter = string.Format("(&(SAMAccountName={0}))", LoginName);

    var user = directorySearcher.FindOne();
    if (user != null)
    {
        x = "Found";
    }
    return Json(x, JsonRequestBehavior.DenyGet);

}

The JQuery script used to call this action method:

        var LoginName = document.getElementById('_LoginName').value;
        var requestData = {
             LoginName :LoginName 
            };

        $.ajax({
         url: '/ControllerName/SearchAd',
         type: 'POST',
         data: JSON.stringify(requestData),
         dataType: 'json',
         contentType: 'application/json; charset=utf-8',
         error: function (xhr) {
            alert('Error: ' + xhr.statusText);
         },
         success: function (result) {
            alert(result);
         },
         async: true,
         processData: false
      });