主题：关于快递API中的ＭＤ5加密的问题

 老师

      在快宝快递API 的开发文档中C#的函数如下:

     public static string GetMd5(string md5str, int type)
    {
        if (type == 16)
        {
            MD5 algorithm = MD5.Create();
            byte[] data = algorithm.ComputeHash(Encoding.UTF8.GetBytes(md5str));
            string sh1 = "";
            for (int i = 0; i < data.Length; i++)
            {
                sh1 += data[i].ToString("x2").ToUpperInvariant();
            }
            return sh1.Substring(8, 16).ToLower();
        }
        else if (type == 32)
        {
            MD5 algorithm = MD5.Create();
            byte[] data = algorithm.ComputeHash(Encoding.UTF8.GetBytes(md5str));
            string sh1 = "";
            for (int i = 0; i < data.Length; i++)
            {
                sh1 += data[i].ToString("x2").ToUpperInvariant();
            }
            return sh1.ToLower();
        }
        return "";
    }

    我按论坛上的代码转换成VB.net 代码如下:

 

    Public Shared Function GetMd5(ByVal md5str As String, ByVal type As Integer) As String
    If type = 16 Then
        Dim algorithm As MD5 = MD5.Create()
        Dim data As Byte() = algorithm.ComputeHash(Encoding.UTF8.GetBytes(md5str))
        Dim sh1 As String = ""

        For i As Integer = 0 To data.Length - 1
            sh1 += data(i).ToString("x2").ToUpperInvariant()
        Next

        Return sh1.Substring(8, 16).ToLower()
    ElseIf type = 32 Then
        Dim algorithm As MD5 = MD5.Create()
        Dim data As Byte() = algorithm.ComputeHash(Encoding.UTF8.GetBytes(md5str))
        Dim sh1 As String = ""

        For i As Integer = 0 To data.Length - 1
            sh1 += data(i).ToString("x2").ToUpperInvariant()
        Next

        Return sh1.ToLower()
    End If

    Return ""
End Function

但是    Dim algorithm As MD5 = MD5.Create() 这句会报错,说不存在 MD5 ,请问老师要怎么改 ?