Calculate Folder (Directory) size in ASP.Net using C# and VB.Net

Hi. I have few folders (1001, 1002, 1003) inside folder named [Uploads], how can i show folder size of [1001] only? The following is my code, it will display all the folder size inside [Uploads]

Private Sub BindData_folder()
    Dim path As String = System.Web.HttpContext.Current.Server.MapPath(System.Web.HttpContext.Current.Request.ApplicationPath & "/Uploads/")
    Dim directories As List(Of ListItem) = New List(Of ListItem)()
    For Each directoryPath As String In Directory.GetDirectories(path)
        directories.Add(New ListItem(New DirectoryInfo(directoryPath).Name, GetDirectorySize(directoryPath)))
    Next
    Me.gvDirectories.DataSource = directories
    Me.gvDirectories.DataBind()
End Sub