C# 常见Url操作实例正则表达式匹配URl

一、将相对url转换成绝对url 方法

//将相对uri转换成绝对uri 实例
Uri uri = new Uri("http://www.gongjuji.net");
Uri uri2 = new Uri(uri, "abc/1234.html");
Console.WriteLine(uri2.ToString());//http://www.gongjuji.net/abc/1234.html
Uri uri3 = new Uri(uri, "/md5/encrypt");
Console.WriteLine(uri3.ToString());//http://www.gongjuji.net/md5/encrypt

实例1：

string s = "例如：http://www.asd.com,http://wwww.gongjuji.net?name=zhangsan&age=10,http://md5.gongjuji.net/dencrypt/";
Regex re = new Regex(@"(?<url>http(s)?://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?)");
MatchCollection mc = re.Matches(s);
foreach (Match m in mc)
{
    string url = m.Result("${url}");
    Console.WriteLine(url);
}

string s = "例如：http://www.asd.com";
Regex re = new Regex(@"(?<url>http(s)?://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?)");
MatchCollection mc = re.Matches(s);
foreach (Match m in mc)
{
    s = s.Replace(m.Result("${url}"), String.Format("<a href='{0}'>{0}</a>", m.Result("${url}")));
}
Console.WriteLine(s);

四、判断字符串是否是URL

/// <summary>
/// 验证是否是URL链接
/// </summary>
/// <param name="str">指定字符串</param>
/// <returns></returns>
public static bool IsURL(string str)
{
    string pattern = @"^(https?|ftp|file|ws)://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?$";
    return IsMatch(pattern, str);
}

/// <summary>
/// 判断一个字符串，是否匹配指定的表达式(区分大小写的情况下)
/// </summary>
/// <param name="expression">正则表达式</param>
/// <param name="str">要匹配的字符串</param>
/// <returns></returns>
public static bool IsMatch(string expression, string str)
{
    Regex reg = new Regex(expression);
    if (string.IsNullOrEmpty(str))
        return false;
    return reg.IsMatch(str);
}

三、url中添加或修改参数�0�2

public static void Test4()
{
    //生成random
    Random rand = new Random(Environment.TickCount);
    int num = rand.Next(1, 100);

    /*
    * http://news.sina.com.cn
    * http://news.sina.com.cn?page=1
    * http://news.sina.com.cn?page=1&ts=1341                         &&
    * http://news.sina.com.cn?ts=14321&page=1                        ?&
    * http://news.sina.com.cn?u=2&ts=14321&page=1                     &&
    */
    string url = "http://news.sina.com.cn?u=2&ts=14321&page=1";
    string ParamText = "ts";
    string ParamValue = num.ToString();
    Console.WriteLine(BuildUrl(url, ParamText, ParamValue));
    Console.Read();
}
//url里有key的值，就替换为value,没有的话就追加.
public static string BuildUrl(string url, string ParamText, string ParamValue)
{
    Regex reg = new Regex(string.Format("{0}=[^&]*", ParamText), RegexOptions.IgnoreCase);
    Regex reg1 = new Regex("[&]{2,}", RegexOptions.IgnoreCase);
    string _url = reg.Replace(url, "");
    if (_url.IndexOf("?") == -1)
        _url += string.Format("?{0}={1}", ParamText, ParamValue);//?
    else
        _url += string.Format("&{0}={1}", ParamText, ParamValue);//&
    _url = reg1.Replace(_url, "&");
    _url = _url.Replace("?&", "?");
    return _url;
}