Making a simple page that returns JSON-formatted data using ASP .net

Question

I am new to ASP. I want to make an ASP page that would return on request JSON formatted data. I followed a few tutorials and all i can see now is the link of a full fledged page with callbacks in my code. So in essence the server is ouptputting a lot of HTML which obviously is not valid JSON. So my only question is how do I go about making such a web page. I want my application to be designed such that when I go to a web page, say http://localhost:8080 (or something similar), a callback or a function in my C# code connects to the database, gathers some info and sends it back as the Response in valid JSON. I'm not looking for libraries which can achieve the same effect, but something like how do I achieve it by simply using a set of Response.Write statements.

Please pardon me if I may give the idea that I am not coherent with my concepts, because I'm really new to this entire thing.

Any help is greatly appreciated.

Regards, p1n3appl3

EDIT: I'm currently using the following JavaScript code:

var xhr = new XMLHttpRequest();
xhr.open("POST", "http://localhost:47949/Default.aspx/NameChange");
xhr.onreadystatechange = function () {
    if (xhr.readyState == 4 && xhr.status == 200) {
        alert(xhr.responseText);
    }
}

xhr.send("");

It makes the call and all, everything's fine but the problem is that it returns the entire code of the "Default.aspx" page again. I mean, the method NameChange isn't even called (I've tested this by setting breakpoints).

What am I doing wrong?

Darin Dimitrov · Accepted Answer · 2011-07-10 13:18:29Z

3

You could define a PageMethod on your page:

public partial class _Default : Page 
{
    [WebMethod]
    public static SomeObject GetObject()
    {
        SomeObject result = ... fetch from db or something
        return result;
    }
}

or you could also do this manually using the JavaScriptSerializer class:

public partial class _Default : Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Clear();
        Response.ContentType = "application/json";
        SomeObject result = ... fetch from db or something
        var serializer = new JavaScriptSerializer();
        string json = serializer.Serialize(result);
        Response.Write(json);
    }
}

answered Jul 10, 2011 at 13:18

Darin Dimitrov

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6 Comments

ssingh Over a year ago

Thanks a lot for the prompt reply. I tried the above code, but it sort of is failing to work. I have a feeling this is because when requesting a URL [in my case, http://localhost/Default.aspx/GetObject] I'm just putting the URL in the browser's URL bar and this causes it to make the call using the HTTP GET method. Am I required to use POST instead. Because, currently, I'm just being redirected to the Default page.

Darin Dimitrov Over a year ago

@user837610, yes Page methods are only accessible with POST requests. You cannot invoke them directly with a GET request such as /Default.aspx/GetObject. You could try the second approach or write a custom generic handler.

ssingh Over a year ago

Well, I'm mostly going to be using it from an XHR object itself, so it's not really a concern that GET requests don't work. anyways, thanks a lot for the help :)

ssingh Over a year ago

Please check the edited question and see if you can help me with this.

Darin Dimitrov Over a year ago

@user837610, you need to set the proper request content type header to application/json. Look at the example I've linked which uses jquery: encosia.com/…

|

user2095113 · Accepted Answer · 2016-05-26 07:51:23Z

1

string jsonProperty = Request["JSonProperty"];//your result
if (!string.IsNullOrEmpty(jsonProperty))
{                    
    Response.Clear();
    Response.ContentType = "application/json";
    Response.Write(RenderJSon());

    Response.Flush();                    // Flush the data to browser
    Response.SuppressContent = true;     // Suppress further output - "standard" html-
                                         // content is not rendered after this

    return;
}

answered May 26, 2016 at 7:51

user2095113

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