Why doesn't my XmlReader.GetAttribute() return a value?

Question

I'm trying to parse my XML in C#.

Here's part of the file that is relevant:

<holder name="wnd_login" width="300" x="20" height="180">...</holder>

Here's the code that is supposed to read it:

while (reader.Read())
{
    if (reader.IsStartElement())
    {
        switch (reader.Name)
        {
            case "holder":
                Holder holder = new Holder(reader.GetAttribute("name"));
                ...
        }
    }
}

I read around that the common mistake was to forget a check to see if the element was a start element. I added it but the GetAttribute still returns null. Any idea?