C# 从文件夹中的树节点下载

**我可以从IT文件夹中下载文件，但如果IT文件夹中有一个文件夹，我想从该文件夹中下载某些内容，则无法下载。 有人知道如何使文件夹中的所有内容都可以下载吗？

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谢谢你能把OutputDirectory的代码贴出来吗？

protected void Page_Load(object sender, EventArgs e)
{

    field1.Text = (string)(Session["rolename"]); //from the page before. eg:IT Folder
    field2.Text = (string)(Session["fullname"]);

    if (Page.IsPostBack == false)
    {

        System.IO.DirectoryInfo RootDir = new System.IO.DirectoryInfo("C:\\Documents and Settings\\itdept\\Desktop\\Files\\"+ field1.Text);
        TreeNode RootNode = OutputDirectory(RootDir, null);
         MyTree.Nodes.Add(RootNode);
    }
}

protected void click(object sender, EventArgs e) //onselectednodechanged from the treenode in aspx page
{
   string file = ("C:\\Documents and Settings\\itdept\\Desktop\\Files\\" + field1.Text + "\\" + MyTree.SelectedValue);
     Response.Clear();
    Response.AppendHeader("Content-Disposition", "attachment;filename=" + file);
    Response.ContentType = "text/xml";
    Response.WriteFile(file); // here is the problem
    Response.End();

}