Proper Way To Find The Form

Today I ran across some code in a 3rd party open source library that used the following function in order to retrieve the form id.

public static string GetPageFormID(Control page)
{
    string id = null;

    foreach (Control con in page.Controls)
    {
        if (con is HtmlForm)
        {
            id = con.ClientID;
            break;
        }
    }
    return id;
}

Which gets called like so:

Control page = HttpContext.Current.Page;
string formID = GetPageFormID(page);

Unfortunately this didn’t work for me because I don’t have the form declared as a direct child of the page. Instead the page contains a user control which contains the form. This is a common scenario when using a MasterPage (in my case an ASP.NET 1.1 backported master page control). When looking for the form, the function should search recursively like so:

public static string GetPageFormID(Control page)
{
    string id = null;

    foreach (Control con in page.Controls)
    {
        if (con is HtmlForm)
        {
            return con.ClientID;
        }
        id = GetPageFormID(con);
        if(id != null)
            return id;
    }
    return id;
}

This will search the entire control hierarchy until it finds the HtmlForm. In the most common case, it will find it without having to recurse. But for crazy folks like me who always look for ways to be different, this will do the trick. Luckily this was an open source library I was using so I was able to fix the code and send the authors a patch.