How can I use the button tag with ASP.NET?

Question

I\'d like to use the newer tag in an ASP.NET website which, among other things, allows CSS-styled text and embedding a graphic inside the button.

Answer 1

I stumbled upon your question looking for the same exact thing. I ended up using Reflector to figure out how the ASP.NET Button control is actually rendered. It turns out to be really easy to change.

It really just comes down to overriding the TagName and TagKey properties of the Button class. After you've done that, you just need to make sure you render the contents of the button manually since the original Button class never had contents to render and the control will render a text-less button if you don't render the contents.

Update:

It's possible to make a few small modifications to the Button control through inheritance and still work fairly well. This solution eliminates the need to implement your own event handlers for OnCommand (although if you want to learn how to do that I can show you how that is handled). It also fixes the issue of submitting a value that has markup in it, except for IE probably. I'm still not sure how to fix IE's poor implementation of the Button tag though. That may just be a truly technical limitation that is impossible to work around...

[ParseChildren(false)]
[PersistChildren(true)]
public class ModernButton : Button
{
    protected override string TagName
    {
        get { return "button"; }
    }

    protected override HtmlTextWriterTag TagKey
    {
        get { return HtmlTextWriterTag.Button; }
    }

    // Create a new implementation of the Text property which
    // will be ignored by the parent class, giving us the freedom
    // to use this property as we please.
    public new string Text
    {
        get { return ViewState["NewText"] as string; }
        set { ViewState["NewText"] = HttpUtility.HtmlDecode(value); }
    }

    protected override void OnPreRender(System.EventArgs e)
    {
        base.OnPreRender(e);
        // I wasn't sure what the best way to handle 'Text' would
        // be. Text is treated as another control which gets added
        // to the end of the button's control collection in this 
        //implementation
        LiteralControl lc = new LiteralControl(this.Text);
        Controls.Add(lc);

        // Add a value for base.Text for the parent class
        // If the following line is omitted, the 'value' 
        // attribute will be blank upon rendering
        base.Text = UniqueID;
    }

    protected override void RenderContents(HtmlTextWriter writer)
    {
        RenderChildren(writer);
    }
}

To use this control, you have a few options. One is to place controls directly into the ASP markup.

You can also add the controls to the control collection of the button in your code-behind.

// This code probably won't work too well "as is"
// since there is nothing being defined about these
// controls, but you get the idea.
btnLogin.Controls.Add(new Label());
btnLogin.Controls.Add(new Table());

I don't know how well a combination of both options works as I haven't tested that.

The only downside to this control right now is that I don't think it will remember your controls across PostBacks. I haven't tested this so it may already work, but I doubt it does. You'll need to add some ViewState management code for sub-controls to be handled across PostBacks I think, however this probably isn't an issue for you. Adding ViewState support shouldn't be terribly hard to do, although if needed that can easily be added.