How to read XML from service and not local path

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XML

Hello everyone, i have a webform where i'm trying to get data from a XML URL.
It works when i read the XML file from my local project but not when i try to read from the URL.
What am i doing wrong here?

What I have tried:

This works:

protected void Page_Load(object sender, EventArgs e)
{
DataSet ds = new DataSet();
ds.ReadXml(Server.MapPath("MynewXML.xml"));
DetailsView2.DataSource = ds.Tables[0].DefaultView;
DetailsView2.DataBind();
}

This does not work:

protected void Page_Load(object sender, EventArgs e)
{
DataSet ds = new DataSet();
ds.ReadXml(Server.MapPath("http://myservername.mydomain.com/my-services/user/MynewXML.xml"));
GridView4.DataSource = ds.Tables[0].DefaultView;
GridView4.DataBind();
}