C＃：如何在Javascript中使用全局变量

Question

everyone! I'm learning ASP.NET MVC and have some question. My problem is Passing Data from View to Controller.

This my Code:

@{
    string listID = "";
}

and I try to use this variable:

function SubmitDelete() {
   var listId = "";        
   var x = document.getElementsByName("IsCheck");
   for (var i = 0; i < x.length; i++) {
     if (x[i].checked == true) {
        listId += x[i].value + ", ";
     };
   }
   @listID = listId;
   return listId;
}

Finalize, I want to pass @listID to Controller:

@using (Html.BeginForm("DeleteChecked", "Category", new { listID }, FormMethod.Post)){ }

It is simple problem about multi delete with checkbox. Help me, please.

Answer 1

You cannot pass a javascript variable to your controller.

But you can post it as part form data with the help of hidden field.

Better add a hidden field and set it in a Javascript and post

@using (Html.BeginForm("DeleteChecked", "Category", FormMethod.Post)){ 

 Html.HiddenFieldFor(m=>m.MyList, new {@id="my-list-data"})

 ..other controls and your submit button

}

In a Javascript

function SubmitDelete() {
   var listId = "";        
   var x = document.getElementsByName("IsCheck");
   for (var i = 0; i < x.length; i++) {
     if (x[i].checked == true) {
        listId += x[i].value + ", ";
     };
   }
   $('#my-list-data').val(listId);

}

Answer 2

You cannot do that.
The aspx\\ascx\\cshtml etc. page is built in the server side while the js is computed on the client's side.
You can add C# string to js functions but they will be hard coded when they get to the client.
All the C# expression are evaluated before they get to the client and before the js is computed.

Here's an example: This is what you see on the aspx\\ascx\\cshtml file.

<%
string str = 'test';
%>
function jsFunc(){
var myVar = '<%=str%>';
}

This is what the client gets:

function jsFunc(){
var myVar = 'test';
}