C#实现HttpUtility.UrlEncode输出大写字母

 在c#中,HttpUtility.UrlEncode("www+mzwu+com")编码结果为www%2bmzwu%2bcom，在和Java开发的平台做对接的时候，对方用用url编码后再对其进行MD5加密，url编码之后的字符串为大(www%2Bmzwu%2Bcom)写这样加密出来的字符串就.net平台的不匹配，

以下供上方法就是解决HttpUtility.UrlEncode编码由小写转化为大写字母

/// <summary>
/// 实现HttpUtility.UrlEncode输出大写字母
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
public static string UrlEncode(string str)
{
    StringBuilder builder = new StringBuilder();
    foreach (char c in str)
    {
        if (c == '+')
        {
            builder.Append("%2B");
        }
        else if (c == ' ')
        {
            builder.Append("%20");
        }
        else
        {
            int len = HttpUtility.UrlEncode(c.ToString()).Length;
            if (len > 1)
            {
                builder.Append(HttpUtility.UrlEncode(c.ToString()).ToUpper());
            }
            else
            {
                builder.Append(c);
            }
        }
    }
    return builder.ToString();
}