How to return a JSON object in standard web forms

问题:

The objective is to call a method which does it's thing then returns a JSON object.

I'm new to JSON.

I have a default.aspx and in it the following code. Now I want an ordinary method in Default.aspx.cs to run on the click event here.

$(".day").click(function (event) {
var day = $(event.currentTarget).attr('id');
if (day != "") {
    $.ajax(
    {
        type: "POST",
        async: true,
        url: 'Default.aspx?day=' + day,
        data: day,
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (msg) {
            console.log("SUCCESS:" + msg);
            //  $(".stripp img").attr('src', "data:image/jpg;" + msg);
            //  $(".stripp").show();
        },
        error: function (msg) {
            console.log("error:" + msg);
        }
    });
}

});

Default.aspx.cs looks similar to this:

    protected void Page_Load(object sender, EventArgs e)
    {
        if (Request.QueryString["day"] != null)
            GetFile(Request.QueryString["day"]);
    }
    public string GetFile(string day)
    {
        string json = "";
        byte[] bytes = getByteArray();

        json = JsonConvert.SerializeObject(bytes);
        return json;
    }

Where am I going wrong here? Should I be using this in some way or is it only applicable in Web Services?

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]

回答1:

I would suggest an HttpHandler. No page lifecycle (so it is blazing fast) and much cleaner code-separation, as well as reusability.

Add a new item to your project of type "Generic Handler". This will create a new .ashx file. The main method of any class that implements IHttpHandler is ProcessRequest. So to use the code from your original question:

public void ProcessRequest (HttpContext context) {

    if(String.IsNullOrEmpty(context.Request["day"]))
    {
        context.Response.End(); 
    }

    string json = "";
    byte[] bytes = getByteArray();

    json = JsonConvert.SerializeObject(bytes);
    context.Response.ContentType = "text/json";
    context.Response.Write(json);
}

Change the url in your AJAX call and that should do it. The JavaScript would look like this , where GetFileHandler.ashx is the name of the IHttpHandler you just created:

$.ajax(
    {
        type: "POST",
        async: true,
        url: 'Handlers/GetFileHandler.ashx',
        data: "Day=" + $.toJSON(day),
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (msg) {
            console.log("SUCCESS:" + msg);
        },
        error: function (msg) {
            console.log("error:" + msg);
        }
    });

Another small point to consider, if you need access to the Session object from within the Handler code itself, make sure to inherit from the IRequiresSessionState interface:

public class GetFileHandler : IHttpHandler, IRequiresSessionState

回答2:

Yes your method has to be static with the WebMethod attribute

Basic example:

CS

using System;
using System.Web.Services;

public partial class _Default : System.Web.UI.Page
{
  [WebMethod(EnableSession=false)]
  public static string HelloWorld()
  {
    return "Hello World";
  }
}

Javascript

<script>
    $.ajax({
      type: "POST",
      url: "Default.aspx/HelloWorld",
      data: "{}",
      contentType: "application/json",
      dataType: "json",
      success: function(msg) {
        console.log(msg.d);
      }
    });
</script>

回答3:

Been a while since I worked with webforms, but if remember correctly it should work if you put the webmethod attribute over GetFile method and make that method static.

 [WebMethod]
 public static string GetFile(string day)

Furthermore, how you post data in ajax method is a bit off. Remove querystring day from url and data should be in json format, something like {"day":day}