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replace links in string with my link

i want to replace every link(s) in a string with the link i want to provide. What i have tried is-
StreamReader reader = new StreamReader(dd1.SelectedItem.Value);
string readFile = reader.ReadToEnd();
Regex regx = new Regex("http(s)?://([\\w+?\\.\\w+])+([a-zA-Z0-9\\~\\!\\#\\#\\$\\%\\^\\&\\*\\(\\)_\\-\\=\\+\\\\\\/\\?\\.\\:\\;\\'\\,]*([a-zA-Z0-9\\?\\#\\=\\/]){1})?", RegexOptions.IgnoreCase);
string output=regx.ToString();
output = readFile;
MatchCollection matches = regx.Matches(output);
foreach (Match match in matches)
{
output = output.Replace(#"match.Value", #"http://localhost:61187/two?" + "sender=" + Server.UrlEncode(this.txtUsername.Text) + "&reciever=" + output);
}
Here, i have a string output which contains some links. So, i have used regex to parse the links in the string. But, the string named "output" is not read and its neither showing an error nor an output.

It seems to me that you should be using regx.Replace(...) instead:
StreamReader reader = new StreamReader(dd1.SelectedItem.Value);
string readFile = reader.ReadToEnd();
Regex regx = new Regex("http(s)?://([\\w+?\\.\\w+])+([a-zA-Z0-9\\~\\!\\#\\#\\$\\%\\^\\&\\*\\(\\)_\\-\\=\\+\\\\\\/\\?\\.\\:\\;\\'\\,]*([a-zA-Z0-9\\?\\#\\=\\/]){1})?", RegexOptions.IgnoreCase);
string output = regx.ToString();
output = readFile;
string username = Server.UrlEncode(this.txtUsername.Text);
output = regx.Replace(output, new MatchEvaluator((match) =>
{
var url = Uri.EscapeDataString(match.Value);
return $"http://localhost:61187/two?sender={username}&receiver={url}";
}));
This will replace every match with the URL returned by the anonymous function.

Find substring between slashes and replace that part in ASP.NET C#

Using ASP.NET C#, I need to find and replace the word string1 between the last two slashes and replace with string2
Example:
string fullStr = "/this/is/string1/part";
string subStr = "function";
string finalStr = "/this/is/" + subStr + "/part";

And a regex solution:
string fullStr = "this/is/string1/part";
string subStr = "function";
var newstr = Regex.Replace(fullStr, #"/[^/]+/(?=[^/]+$)", m => "/" + subStr + "/");

I don't feel a need of regex here.
string fullStr = "/this/is/string1/part";
string subStr = "function";
string[] fullStrParts = fullStr.Split('/');
fullStrParts[fullStrParts.Length - 2] = subStr;
string finalStr = string.Join("/", fullStrParts);

Extract all strings between [ text1 ] [text2] tags

I have an sql text that includes
"Select * from Table Where [PARAM1] = [PARAM2] ..."
I want to get list between "[" "]" tags to list.
How can I do it ?

You can do it using LINQ
string str = "Select * from Table Where [PARAM1] = [PARAM2] ...";
string[] Array = str.Split().Where(r=> r.StartsWith("[") && r.EndsWith("]"))
.Select(r=> r.Trim('[',']'))
.ToArray();

Use this snippet
string strRegex = #"\[(.*?)\]";
RegexOptions myRegexOptions = RegexOptions.IgnoreCase;
Regex myRegex = new Regex(strRegex, myRegexOptions);
string strTargetString = #"Select * from Table Where [PARAM1] = [PARAM2] ...";
foreach (Match myMatch in myRegex.Matches(strTargetString))
{
// myMatch.Groups[0] - your string
}

You can try using regular expressions and some LINQ:
Regex t = new Regex(#"\[([^]]*)\]");
List<String> parameters = t.Matches(input_string).Cast<Match>().Select(a => a.Groups[1].ToString()).ToList();
This will result in a List holding the two matches PARAM1 and PARAM2

You can also do
List<string> matches=Regex.Matches(#"(?<=\[)[^\[\]]*(?=\])")
.Cast<Match>()
.Select(x=>x.Value)
.ToList();

Here is what you need:
Regex t = new Regex(#"\[(.*?)\]");
string str = #"Select * from Table Where [PARAM1] = [PARAM2] ...";
foreach (Match myMatch in myRegex.Matches(str))
{
// myMatch.Groups[0] and so on....
}
Live Demo

To convert a MatchCollection to List use:
List<Match> myMatches = Regex.Matches("bla", #"\[[^]]*)\]").Cast<Match>.toList();

You can try using this regular expression:
Regex regex = new Regex(#"\[.*?\]");
var parameters = regex.Matches(sqlQueryString);

Facebook feed - remove extra Facebook JS from anchor

Please help me to replace all the additional Facebook information from here using C# .net Regex Replace method.
Example
http://on.fb.me/OE6gnBsomehtml
Output
somehtml on.fb.me/OE6gnB somehtml
I tried following regex but they didn't work for me
searchPattern = "<a([.]*)?/l.php([.]*)?(\">)?([.]*)?(</a>)?";
replacePattern = "$3";
Thanks

I manage to do this using regex with following code
searchPattern = "<a(.*?)href=\"/l.php...(.*?)&?(.*?)>(.*?)</a>";
string html1 = Regex.Replace(html, searchPattern, delegate(Match oMatch)
{
return string.Format("{1}", HttpUtility.UrlDecode(oMatch.Groups[2].Value), oMatch.Groups[4].Value);
});

You can try this (System.Web has to be added to use System.Web.HttpUtility):
string input = #"http://on.fb.me/OE6gnBsomehtml";
string rootedInput = String.Format("<root>{0}</root>", input);
XDocument doc = XDocument.Parse(rootedInput, LoadOptions.PreserveWhitespace);
string href;
var anchors = doc.Descendants("a").ToArray();
for (int i = anchors.Count() - 1; i >= 0; i--)
{
href = HttpUtility.ParseQueryString(anchors[i].Attribute("href").Value)[0];
XElement newAnchor = new XElement("a");
newAnchor.SetAttributeValue("href", href);
newAnchor.SetValue(href.Replace(#"http://", String.Empty));
anchors[i].ReplaceWith(newAnchor);
}
string output = doc.Root.ToString(SaveOptions.DisableFormatting)
.Replace("<root>", String.Empty)
.Replace("</root>", String.Empty);

Saving an XML that has invalid characters

there are code snippets that strip the invalid characters inside a string before we save it as an XML ... but I have one more problem: Let's say my user wants to have a column name like "[MyColumnOne] ...so now I do not want to strip these "[","] well because these are the ones that user has defined and wants to see them so if I use some codes that are stripping the invalid characters they are also removing "[" and "[" but in this case I still need them to be saved... what can I do?

Never mind, I changed my RegEx format to use XML 1.1 instead of XML 1.0 and now it is working good :
string pattern = String.Empty;
//pattern = #"#x((10?|[2-F])FFF[EF]|FDD[0-9A-F]|7F|8[0-46-9A-F]9[0-9A-F])"; //XML 1.0
pattern = #"#x((10?|[2-F])FFF[EF]|FDD[0-9A-F]|[19][0-9A-F]|7F|8[0-46-9A-F]|0?[1-8BCEF])"; // XML 1.1
Regex regex = new Regex(pattern, RegexOptions.IgnoreCase);
if (regex.IsMatch(sString))
{
sString = regex.Replace(sString, String.Empty);
File.WriteAllText(sString, sString, Encoding.UTF8);
}
return sString;

This worked for me, and it was fast.
private object NormalizeString(object p) {
object result = p;
if (p is string || p is long) {
string s = string.Format("{0}", p);
string resultString = s.Trim();
if (string.IsNullOrWhiteSpace(resultString)) return "";
Regex rxInvalidChars = new Regex("[\r\n\t]+", RegexOptions.IgnoreCase);
if (rxInvalidChars.IsMatch(resultString)) {
resultString = rxInvalidChars.Replace(resultString, " ");
}
//string pattern = String.Empty;
//pattern = #"";
////pattern = #"#x((10?|[2-F])FFF[EF]|FDD[0-9A-F]|7F|8[0-46-9A-F]9[0-9A-F])"; //XML 1.0
////pattern = #"#x((10?|[2-F])FFF[EF]|FDD[0-9A-F]|[19][0-9A-F]|7F|8[0-46-9A-F]|0?[1-8BCEF])"; // XML 1.1
//Regex rxInvalidXMLChars = new Regex(pattern, RegexOptions.IgnoreCase);
//if (rxInvalidXMLChars.IsMatch(resultString)) {
// resultString = rxInvalidXMLChars.Replace(resultString, "");
//}
result = string.Join("", resultString.Where(c => c >= ' '));
}
return result;
}