How to use a class for xml related logic taking xml file "uri" as initializer?

Question

Hi ,
i have a project in which i created two classes TreeDisplay(Form.cs) and MytreeNode class in same namespace.
TreeDisplay class contains all the GUI related stuff like Browse button textbox,label,progress bar and TReeView. I want the user to select a XML file through browse button which will be displayed in textbox.The Xml file selected will be displayed in Treeview on winform.

Now i want to separate the GUI part from business logic(where i am creating treenode and adding nodes to tree) thats why i created the MytreeNode class. I am passing the treeview and the string filename from the FileOpenDialogue in Browse button.

i want to pass a Xml file name from one class to another class in same namespace using URI.i want to initialize with file path. i have passed the treeview object from GUI to my backhand class MytreeNode class.
But how to initialize with fie path? here is a part of code of MytreeNode class.

enter code here
public class MytreeNodeClass
{
    internal void initiatingTree(string nameofFile,TreeView treeView1)
    {
        try
        {
            XmlDocument xmlDocument = new XmlDocument();
            xmlDocument.Load(nameofFile);
            treeView1.Nodes.Clear();
            if (xmlDocument.DocumentElement != null)
                if (true) treeView1.Nodes.Add(new TreeNode(xmlDocument.DocumentElement.Name));

Help me in putting up the right part of code at right place. :-( ??
Thanks