C#获取URL参数值办法

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/// 测试.
/// 
public void Test()
{
 //或者动态读取前一次的URL
 //string parmStr = Request.UrlReferrer.Query;
 //NameValueCollection col = GetQueryString(parmStr);
    string pageURL = "http://www.google.com.hk/search?hl=zh-CN&source=hp&q=%E5%8D%9A%E6%B1%87%E6%95%B0%E7%A0%81&aq=f&aqi=g2&aql=&oq=&gs_rfai=";
    Uri uri = new Uri(pageURL);
    string queryString = uri.Query;
    NameValueCollection col = GetQueryString(queryString);
    string searchKey = col["q"];
    //结果 searchKey = "机械数控"
}    

/// 

/// 将查询字符串解析转换为名值集合.
/// 
/// 
/// 
public static NameValueCollection GetQueryString(string queryString)
{
    return GetQueryString(queryString, null, true);
}

/// 

/// 将查询字符串解析转换为名值集合.
/// 
/// 
/// 
/// 
/// 
public static NameValueCollection GetQueryString(string queryString, Encoding encoding, bool isEncoded)
{
    queryString = queryString.Replace("?", "");
    NameValueCollection result = new NameValueCollection(StringComparer.OrdinalIgnoreCase);
    if (!string.IsNullOrEmpty(queryString))
    {
        int count = queryString.Length;
        for (int i = 0; i < count; i++)
        {
            int startIndex = i;
            int index = -1;
            while (i < count)
            {
                char item = queryString[i];
                if (item == '=')
                {
                    if (index < 0)
                    {
                        index = i;
                    }
                }
                else if (item == '&')
                {
                    break;
                }
                i++;
            }
            string key = null;
            string value = null;
            if (index >= 0)
            {
                key = queryString.Substring(startIndex, index - startIndex);
                value = queryString.Substring(index + 1, (i - index) - 1);
            }
            else
            {
                key = queryString.Substring(startIndex, i - startIndex);
            }
            if (isEncoded)
            {
                result[MyUrlDeCode(key, encoding)] = MyUrlDeCode(value, encoding);                    
            }
            else
            {
                result[key] = value;
            }
            if ((i == (count - 1)) && (queryString[i] == '&'))
            {
                result[key] = string.Empty;
            }
        }
    }
    return result;
}

/// 

/// 解码URL.
/// 
/// null为自动选择编码
/// 
/// 
public static string MyUrlDeCode(string str, Encoding encoding)
{
    if (encoding == null)
    {
        Encoding utf8 = Encoding.UTF8;
        //首先用utf-8进行解码                     
        string code = HttpUtility.UrlDecode(str.ToUpper(), utf8);
        //将已经解码的字符再次进行编码.
        string encode = HttpUtility.UrlEncode(code, utf8).ToUpper();
        if (str == encode)
            encoding = Encoding.UTF8;
        else
            encoding = Encoding.GetEncoding("gb2312");
    }
    return HttpUtility.UrlDecode(str, encoding);
}

说明 

1. 对于下面的编码方式中，Baidu是使用gb2312，而Google是使用UTF8的，所以这些编码如何解释呢？解决办法就是如MyUrlDeCode方法所写的，把编码进行一次解码，再把解码后的字符串进行编码，再对字符串进行比较，如果是相同的，那就是使用了这种编码的。还要注意进行ToUpper字符串。

2. string baidu = HttpUtility.UrlDecode("wd=%B2%A9%BB%E3%CA%FD%C2%EB");
   string google = HttpUtility.UrlDecode("q=%E5%8D%9A%E6%B1%87%E6%95%B0%E7%A0%81"); 

    

3. 关于return GetQueryString(queryString, null, true); 如果你传入的是null，那就是表示你无法确认编码是gb2312还是UTF8，当你确认编码的，可以直接传入编码类型，比如return GetQueryString(queryString, Encoding.UTF8, true); 
4. 需要注意queryString = queryString.Replace("?", "");把?给过滤掉。
5. %B2%A9%BB%E3%CA%FD%C2%EB = %B2%A9 %BB%E3 %CA%FD %C2%EB(机械数控gb2312)
6. %E5%8D%9A%E6%B1%87%E6%95%B0%E7%A0%81 = %E5%8D%9A %E6%B1%87 %E6%95%B0 %E7%A0%81(机械数控utf-8)