Public Shared Function Sign(VarPost As NameValueCollection) As String
        '读取私钥
        Dim fs As New FileStream(AppDomain.CurrentDomain.BaseDirectory & "\prkeynet.key", FileMode.Open)
        Dim sr As New StreamReader(fs)
        Dim KeyStr As String = sr.ReadToEnd.ToString

        Dim SignStr As String = ""
        For i As Integer = 0 To VarPost.Count - 1
            SignStr += VarPost.Get(i).ToString & "|"
        Next
         
        Dim RSA As New RSACryptoServiceProvider()
        RSA.FromXmlString(KeyStr)
        Dim AOutput As Byte() = RSA.SignData(Encoding.UTF8.GetBytes(SignStr.Substring(0, SignStr.Length - 1)), "SHA1")

        fs.Close()
        fs.Dispose()

        Return Convert.ToBase64String(AOutput)
    End Function