计算文件md5码

代码如下：

//filePath 文件路径
private string File2MD5(string filePath)
{
    StringBuilder sb = new StringBuilder();
    FileStream fileStream = new FileStream(filePath,FileMode.Open);
    MD5 md5 = new MD5CryptoServiceProvider();
    byte[] bytes = md5.ComputeHash(fileStream);
    for (var i = 0; i < bytes.Length; i++)
    {
        sb.Append(bytes[i].ToString("x2"));
    }
    return sb.ToString();
}