c# - System.XML - Function so slow. Any other suggestions to solve that problem?

   
HI Experts,

I wrote the following function.
I'm calling a website with a special paramter (productid).
I receive an xml-file with the imagename of the products image.
I read this filename and attach it to the img src-path which is known.
but my problem is... it is soooo slow.
Am I doing anything wrong? Is there a faster way?
The pictures are pretty small and not so many. so that can't be the reason.
Please help.
Thanks!!!

call:
imgname = imageresolver.getImageNameFor(item.Key);
imgProduct.Src = @"http://www.address.com/catalog/images/small/" + imgname;
function:
    public string getImageNameFor(string productId)
        {
            string url = "http://www.address.com/default.cfm?productnumber=" + productId;
            System.Net.WebRequest request = System.Net.WebRequest.Create(url);
            System.IO.Stream input = request.GetResponse().GetResponseStream();

            string result = "";

            System.IO.StringWriter writer = new System.IO.StringWriter();

            System.IO.StreamReader streamReader = new System.IO.StreamReader(input);

            XmlTextReader reader = new XmlTextReader(url);
            string name;
            while (reader.Read())
            {        
                name = reader.Name;

                switch (reader.NodeType)
                {
                    case XmlNodeType.Element:
                        if (name.StartsWith("imagefilename", true, null))
                        {
                            result = reader.ReadElementContentAsString();                          
                        };
                        break;

                }
            }
            streamReader.Close();
            input.Close();

            return result;
        }