How to let an ASMX file output JSON

Question

I created an ASMX file with a code behind file. It's working fine, but it is outputting XML.

However, I need it to output JSON. The ResponseFormat configuration doesn't seem to work. My code-behind is:

[System.Web.Script.Services.ScriptService]
public class _default : System.Web.Services.WebService {
    [WebMethod]
    [ScriptMethod(UseHttpGet = true,ResponseFormat = ResponseFormat.Json)]
    public string[] UserDetails()
    {
        return new string[] { "abc", "def" };
    }
}

Answer 1

To receive a pure JSON string, without it being wrapped into an XML, you have to write the JSON string directly to the HttpResponse and change the WebMethod return type to void.

    [System.Web.Script.Services.ScriptService]
    public class WebServiceClass : System.Web.Services.WebService {
        [WebMethod]
        public void WebMethodName()
        {
            HttpContext.Current.Response.Write("{property: value}");
        }
    }