Question

I have a main web page (“Base Page”) that makes an ajax call (using jQuery) to the server. The server-side page (“Ajax Page”) is an ASP.NET web form (no MVC in use here). Because (in this case) I’m using a GridView to render data within the ajax response, I have to include the <form runat=”server”> tag.

My complaint is this–when the Base Page receives the AJAX response, it inserts it into the DOM, but because the AJAX response is comprised of HTML markup that includes a <form> tag, this sometimes results in nested html forms, which is bad.

I realize that I can use jquery to only insert a fragment of the response into the Base Page DOM–or that I could use jquery to subsequently strip out the offending <form> tag. But these feel like klunky work-arounds. Is there really no way to prevent the ASP.NET page from serving out its response with a <form> tag? I realize that the form tag is the heart of the ASP.NET webform model, but it sure makes using AJAX in ASP.NET a complicated affair–very much swimming upstream. Surely Microsoft has realized that the postback / server-side model is a thing of the past?

I also realize that Microsoft has some server-side AJAX libraries that probably address this issue–but I’d still like to know if there’s a solution native to ASP.NET webforms.

Any suggestions?

Answer 1

You can add your GridView to a Web User Control and then render it to a string like this:

public static string ExecuteToString(this Control control)
{
    Page page = new Page();
    page.Controls.Add(control);

    StringBuilder sb = new StringBuilder();
    using (StringWriter writer = new StringWriter(sb))
    {
        HttpContext.Current.Server.Execute(page, writer, false);
    }
    return sb.ToString();
}

This means you don’t need to point your ajax request to a page. You can use a web service. Query a specific method and then dynamically load the User Control, render it to a string and return the HTML. Because you put your HTML and code in a User Control you don’t need to worry about stripping out form tags and you can still use all the asp controls as you would on a page.

I have no idea about the performance costs of using this method but I’ve been using it for a while and it seems fine to me.