.net – How to take more control in ASP.NET

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I'm trying to build a very, very simple "micro-webapp" which I suspect will be of interest to a few Stack Overflow'rs if I ever get it done. I'm hosting it on my C# in Depth site, which is vanilla ASP.NET 3.5 (i.e. not MVC).

The flow is very simple:

  • If a user enters the app with a URL which doesn't specify all the parameters (or if any of them are invalid) I want to just display the user input controls. (There are only two.)
  • If a user enters the app with a URL which does have all the required parameters, I want to display the results and the input controls (so they can change the parameters)

Here are my self-imposed requirements (mixture of design and implementation):

  • I want the submission to use GET rather than POST, mostly so users can bookmark the page easily.
  • I don't want the URL to end up looking silly after submission, with extraneous bits and pieces on it. Just the main URL and the real parameters please.
  • Ideally I'd like to avoid requiring JavaScript at all. There's no good reason for it in this app.
  • I want to be able to access the controls during render time and set values etc. In particular, I want to be able to set the default values of the controls to the parameter values passed in, if ASP.NET can't do this automatically for me (within the other restrictions).
  • I'm happy to do all the parameter validation myself, and I don't need much in the way of server side events. It's really simple to set everything on page load instead of attaching events to buttons etc.

Most of this is okay, but I haven't found any way of completely removing the viewstate and keeping the rest of the useful functionality. Using the post from this blog post I've managed to avoid getting any actual value for the viewstate – but it still ends up as a parameter on the URL, which looks really ugly.

If I make it a plain HTML form instead of an ASP.NET form (i.e. take out runat="server") then I don't get any magic viewstate – but then I can't access the controls programmatically.

I could do all of this by ignoring most of ASP.NET and building up an XML document with LINQ to XML, and implementing IHttpHandler. That feels a bit low level though.

I realise that my problems could be solved by either relaxing my constraints (e.g. using POST and not caring about the surplus parameter) or by using ASP.NET MVC, but are my requirements really unreasonable?

Maybe ASP.NET just doesn't scale down to this sort of app? There's a very likely alternative though: I'm just being stupid, and there's a perfectly simple way of doing it that I just haven't found.

Any thoughts, anyone? (Cue comments of how the mighty are fallen, etc. That's fine – I hope I've never claimed to be an ASP.NET expert, as the truth is quite the opposite…)

Best Answer

This solution will give you programmatic access to the controls in their entirety including all attributes on the controls. Also, only the text box values will appear in the URL upon submission so your GET request URL will be more "meaningful"

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="JonSkeetForm.aspx.cs" Inherits="JonSkeetForm" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Jon Skeet's Form Page</title>
</head>
<body>
    <form action="JonSkeetForm.aspx" method="get">
    <div>
        <input type="text" ID="text1" runat="server" />
        <input type="text" ID="text2" runat="server" />
        <button type="submit">Submit</button>
        <asp:Repeater ID="Repeater1" runat="server">
            <ItemTemplate>
                <div>Some text</div>
            </ItemTemplate>
        </asp:Repeater>
    </div>
    </form>
</body>
</html>

Then in your code-behind you can do everything you need on PageLoad

public partial class JonSkeetForm : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        text1.Value = Request.QueryString[text1.ClientID];
        text2.Value = Request.QueryString[text2.ClientID];
    }
}

If you don't want a form that has runat="server", then you should use HTML controls. It's easier to work with for your purposes. Just use regular HTML tags and put runat="server" and give them an ID. Then you can access them programmatically and code without a ViewState.

The only downside is that you won't have access to many of the "helpful" ASP.NET server controls like GridViews. I included a Repeater in my example because I'm assuming that you want to have the fields on the same page as the results and (to my knowledge) a Repeater is the only DataBound control that will run without a runat="server" attribute in the Form tag.

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