有的時候我們要操作一個URL地址中查詢參數，為了不破壞URL的原有結構，我們一般不能直接在URL的後面加&query=value，特別是我們的URL中有多個參數時，這種處理更麻煩。
下面兩個小方法就是專門用來為一個URL添加一個查詢參數或刪除一個查詢參數，這兩個方法隱藏了原URL有無參數，是不是原來就有這個參數，有沒有fragment(#anchor)這些細節和處理
/**//// <summary>
/// Add a query to an URL.
/// if the URL has not any query,then append the query key and value to it.
/// if the URL has some queries, then check it if exists the query key already,replace the value, or append the key and value
/// if the URL has any fragment, append fragments to the URL end.
/// </summary>
public static string SafeAddQueryToURL(string key,string value,string url)
{
int fragPos = url.LastIndexOf("#");
string fragment = string.Empty;
if(fragPos > -1)
{
fragment = url.Substring(fragPos);
url = url.Substring(0,fragPos);
}
int querystart = url.IndexOf("?");
if(querystart < 0)
{
url +="?"+key+"="+value;
}
else
{
Regex reg = new Regex(@"(?<=[&\?])"+key+@"=[^\s]*",RegexOptions.Compiled);
if(reg.IsMatch(url))
url = reg.Replace(url,key+"="+value);
else
url += "&"+key+"="+value;
}
return url+fragment;
}
/**//// <summary>
/// Remove a query from url
/// </summary>
/// <param name="key"></param>
/// <param name="url"></param>
/// <returns></returns>
public static string SafeRemoveQueryFromURL(string key,string url)
{
Regex reg = new Regex(@"[&\?]"+key+@"=[^\s]*&?",RegexOptions.Compiled);
return reg.Replace(url,new MatchEvaluator(PutAwayGarbageFromURL));
}
private static string PutAwayGarbageFromURL(Match match)
{
string value = match.Value;
if(value.EndsWith("&"))
return value.Substring(0,1);
else
return string.Empty;
}
測試：
string s = "http://www.cnblogs.com/?a=1&b=2&c=3#tag";
WL(SafeRemoveQueryFromURL("a",s));
WL(SafeRemoveQueryFromURL("b",s));
WL(SafeRemoveQueryFromURL("c",s));
WL(SafeAddQueryToURL("d","new",s));
WL(SafeAddQueryToURL("a","newvalue",s));
// 輸出如下:
// http://www.cnblogs.com/?b=2&c=3#tag
// http://www.cnblogs.com/?a=1&c=3#tag
// http://www.cnblogs.com/?a=1&b=2#tag
// http://www.cnblogs.com/?a=1&b=2&c=3&d=new#tag
// http://www.cnblogs.com/?a=newvalue&b=2&c=3#tag
