Overriding ASP.NET Form Action Attribute

As we all know, ASP.NET uses one form model to do all it's magic. Love it or hate it, we have to live with it. 99% of the time, it is not a problem, but then there is this 1%...

The main problem with ASP.NET's model is that the form tag has a fixed action attribute. What if we want to change it? No, there is no simple way of doing it. Solutions vary. Most common one is to create your own FormControl that inherits from HtmlForm and override RenderAttributes method. Unfortunately, inside that method, we have to do everything the original method does and only change the action attribute to the desired value. Ugly!

Another one is to provide an OutputFilter for the Response but that is also a lot of coding.

My preferred way of dealing with this issue is to provide my own, special HtmlTextWriter. Its role is to intercept the WriteAttribute method call and provide my own value. Following code illustrates the concept:

class ActionAttributeWriter
    : HtmlTextWriter
{
    string action;
    public ActionAttributeWriter(
        HtmlTextWriter writer, string action)
        : base(writer)
    {
        this.action = action;
    }
    public override void WriteAttribute
        (string name, string value, bool fEncode)
    {
        if (name == "action")
        {
            value = action; 
        }
        base.WriteAttribute(name, value, fEncode);
    }
}

Only thing that is needed then is to use this writer instead of a normal one. Page.CreateHtmlTextWriter can be used for this purpose:

protected override HtmlTextWriter 
    CreateHtmlTextWriter(System.IO.TextWriter tw)
{
    ActionAttributeWriter writer = 
        new ActionAttributeWriter(
            base.CreateHtmlTextWriter(tw), 
            "action");
    return writer;
}

Solution is not very clean and I would certainly not recommend it for a public product, but it's better than nothing.

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