How to set .asmx webservice Enabling Cross-Origin using Asp.net

Question

My webservice code is

 [WebMethod]
     public List<test> GetMachineData_List(string prefix, int person_id)
     {
         using (var db = new TestDB())
         {
             List<test> list = db.Fetch<test>("select id,name from machine_data_collection mc where mc.id=@0 and name like '%" + prefix + "%'", person_id);
             return list.ToList();
         }
     }

My jquery Ajax call is

 $("#textbx").autocomplete(
            {
                source: function (request, response) {
                 $.ajax({
                        url: 'http://localhost:4787/ws/webservice.asmx/GetMachineData_List',
                        data: { prefix: request.term.toString() ,person_id:1},
                        dataType: "json",
                        type: "POST",
                        contentType: "application/json; charset=utf-8",
                        success: function (data) {
                            var jsonArray;
                            try {
                                jsonArray = $.parseJSON(data.d); // using jQuery
                            } catch (e) {
                                jsonArray = data.d; // using jQuery

                            }
                            response($.map(jsonArray, function (item) {
                                return {
                                    id: item.id,
                                    value: item.Name

                                };
                            }));

                        },
                        error: function (XMLHttpRequest, textStatus, errorThrown) {
                            var msg = XMLHttpRequest.responseJSON.d;
                            if (msg == undefined) {
                                alert( "Something went wrong !!" + errorThrown);
                            } else {
                                alert( "Error"+ msg);
                            }
                        }

                    });
                },
                minLength: 2,
                select: function (event, ui) {
                    var idControl = this.dataset.bindcontrol;
                    try {
                        alert(ui.item.id);

                    }
                    catch (ex) {
                        alert( "Oops .. Something happend unexpected !! .. Please redo ");
                    }
                }
            }

    );

And i enable the Cross-Origin in web.config code is

 <system.webServer>
    <httpProtocol>
      <customHeaders>
          <add name="Access-Control-Allow-Origin" value="http://localhost:21702/" />
          <add name="Access-Control-Allow-Headers" value="X-AspNet-Version,X-Powered-By,Date,Server,Accept,Accept-Encoding,Accept-Language,Cache-Control,Connection,Content-Length,Content-Type,Host,Origin,Pragma,Referer,User-Agent" />
          <add name="Access-Control-Allow-Methods" value="GET, PUT, POST, DELETE, OPTIONS" />
          <add name="Access-Control-Max-Age" value="1000" />
          <add name="Access-Control-Allow-Credentials" value="true" />
        </customHeaders>
    </httpProtocol>
  </system.webServer>

When change text in textbox error occured. Error Meaasge from Ajax call is :

XMLHttpRequest cannot load http://localhost:4787/ws/webservice.asmx/GetMachineData_List. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:21702' is therefore not allowed access. The response had HTTP status code 500.

Solution

Add below code snippet in Web.config file:

  <system.web>
    <webServices>
      <protocols>
        <add name="HttpGet"/>
        <add name="HttpPost"/>
      </protocols>
   </webServices>
 </system.web>
 .............
..............
 <system.webServer>
    <httpProtocol>
      <customHeaders>
        <add name="Access-Control-Allow-Headers" value="accept, content-type" />
        <add name="Access-Control-Allow-Origin" value="http://localhost:4200"/>
        <add name="Access-Control-Allow-Methods" value="POST, GET, OPTIONS" /> 
        **...(add additional add names and values when you need).......**
      </customHeaders>
    </httpProtocol>
  </system.webServer>

In my case <add name="Access-Control-Allow-Origin" value="http://localhost:4200"/> the base url of webservice consumer app (Angular) is http://localhost:4200.

You have to mention your base url in that specific place.