vb.net后台http下载无提示覆盖文件

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim url As String
        url = "http://localhost/system.dll"

        Dim path As String

        path = Environment.CurrentDirectory() & "/system.dll"
        Dim wc As System.Net.WebClient
        wc = New System.Net.WebClient
        wc.DownloadFile(url, path)

    End Sub