如何使用 webbrowser 显示 mht 文件

Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click

WebBrowser1.Navigate("a.mht")

While WebBrowser1.ReadyState <> WebBrowserReadyState.Complete
Application.DoEvents()
End While

Dim reader As New StreamReader(WebBrowser1.DocumentStream, System.Text.Encoding.GetEncoding("GB2312"))
Dim html As String = reader.ReadToEnd()
TextBox1.Text = html
reader.Close()
End Sub

Dim streamReader As New IO.StreamReader("", Encoding.UTF8)
Dim streamReader As New IO.StreamReader("", Encoding.GetEncoding(936))
Dim streamReader As New IO.StreamReader("", Encoding.GetEncoding("GB2312"))