如何在Ajax中启用cors？

Question

I am trying to call data from the following host url test.domain.com/test2.aspx/BindDatatable , however i keep getting 404 response and the following message in my console window:

error message:

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://test.domain.com/test2.aspx. This can be fixed by moving the resource to the same domain or enabling CORS

i have added the following cors header in the web.config file of my host(url ) file:

<system.webServer>
<httpProtocol>
<customHeaders>
<add name="Access-Control-Allow-Origin" value="origin" />
<add name="Access-Control-Request-Method" value="POST" /> 
<add name="Access-Control-Allow-Headers" value="content-type, accept" /> 
</customHeaders>
</httpProtocol>
</system.webServer>

it also contains the following web-method behind test2.aspx.cs:

[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
[WebMethod()]
public static string BindDatatable()
{
    DataTable dt = new DataTable();
    List<UserDetails> details = new List<UserDetails>();

    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["#####"].ConnectionString))
    {
        using (SqlCommand cmd = new SqlCommand("######", con))
        {
            con.Open();
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(dt);
            foreach (DataRow dtrow in dt.Rows)
            {
                UserDetails user = new UserDetails();
                user.Name= dtrow["###"].ToString();
                user.Loan = dtrow["###"].ToString();
                user.Evnt = dtrow["###"].ToString();
                details.Add(user);
            }
        }
    }
     JavaScriptSerializer serializer = new JavaScriptSerializer();
     return serializer.Serialize(details);
}

ajax function called from corsTest.aspx

   $(document).ready(function () {
    $.support.cors = true;
    $.ajax({
        type: "Post",
        crossDomain: true,
        contentType: "application/json; charset=utf-8",
        url: "http://wwww.test.domain.com/test2.aspx/BindDatatable",
        data: "{}",
        dataType: "json",
        success: function (data) {
            alert(data.toSource());
            console.log(data);
            var myData = JSON.parse(data.d)
             for (var i = 0; i < myData.length; i++) {
                 $("#tbDetails").append("<tr><td>" + myData[i].Name + "</td><td>" + myData[i].Loan + "</td><td>" + myData[i].Evnt + "</td></tr>");                    
            }
        },
        error: function (result) {
            alert("Error");
        }
    });
});

I am not sure, what else i am suppose to update further to get this to work. Do I also need, to define the cors header in the head tag of the text2.aspx page as well.

thanks in advance for any further feedback/guide.

Answer 1

I stuck into similar situation today so sharing my solution, hope it could help somebody. I used jsonp to fetch the data from cross domain. Taking your example, if one has access to BindDatatable() method in test2.aspx.cs , then we can modify json object to be returned in the format like jsonData({..your json..}) . By wrapping the method with jsonData(), it could be read by jsonp during ajax call made like:

var url = "http://wwww.test.domain.com/test2.aspx/BindDatatable";
    $.ajax({
                url: url,
                dataType: 'jsonp',
                jsonpCallback: 'jsonData',
                success: function (response) {
                    console.log('callback success: ', response);
                },
                error: function (xhr, status, error) {
                    console.log(status + '; ' + error);
                }
            });

Otherwise as suggested in the above post, you can create a function in your own application corsTest.aspx.cs and access cross domain link through it in C# and return json as shown below:

$.ajax({
    type: "Post",
    contentType: "application/json; charset=utf-8",
    url: "/corsTest.aspx/BindDatatableTest",
    dataType: "json",
    .
    .
    error: function (result) {
        alert("Error");
    }
});

Define function in corsTest.aspx.cs like:

private string BindDatatableTest()
{
    JavaScriptSerializer serializer = new JavaScriptSerializer(); 
    string url = "http://wwww.test.domain.com/test2.aspx/BindDatatable";
    WebClient wc = new WebClient();        
    ServicePointManager.Expect100Continue = false;
    ServicePointManager.MaxServicePointIdleTime = 2000;
    string json = wc.DownloadString(url);
    object jsonData = new
    {
          jsonFinal = jsonD
    };

    return Content(serializer.Serialize(jsonData), "application/json");
}

Also, in order to call cross domain url you have to add the following code to web.config:

<system.net>
    <settings>
      <httpWebRequest useUnsafeHeaderParsing="true" />
    </settings>
  </system.net>

Answer 2

Check if the remote method is available. Check the firewall of the server where the service is hosted if it allows connections for the specific port. Also check on your machine if output port is not blocked.

Another way to enable cors is to make the connection on the server side. For instance you can add service reference to the remote method and use that method on the server side in your local project. Then on the client you have to call only the local method that is within your solution and you don't have to enable cors on the client.