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Find hashtags in string

I am working on a Xamarin.Forms PCL project in C# and would like to detect all the hashtags.
I tried splitting at spaces and checking if the word begins with an # but the problem is if the post contains two spaces like "Hello #World Test" it would lose that the double space
string body = "Example string with a #hashtag in it";
string newbody = "";
foreach (var word in body.Split(' '))
{
if (word.StartsWith("#"))
newbody += "[" + word + "]";
newbody += word;
}
Goal output:
Example string with a [#hashtag] in it
I also only want it to have A-Z a-z 0-9 and _ stopping at any other character
Test #H3ll0_W0rld$%Test => Test [#H3ll0_W0rld]$%Test
Other Stack questions try to detect the string and extract it, I would like it work with it and put it back in the string without losing anything that methods such as splitting by certain characters would lose.

You can use Regex with #\w+ and $&
Explanation
# matches the character # literally (case sensitive)
\w+ matches any word character (equal to [a-zA-Z0-9_])
+ Quantifier — Matches between one and unlimited times, as many times as possible, giving back as needed (greedy)
$& Includes a copy of the entire match in the replacement string.
Example
var input = "asdads sdfdsf #burgers, #rabbits dsfsdfds #sdf #dfgdfg";
var regex = new Regex(#"#\w+");
var matches = regex.Matches(input);
foreach (var match in matches)
{
Console.WriteLine(match);
}
or
var result = regex.Replace(input, "[$&]" );
Console.WriteLine(result);
Ouput
#burgers
#rabbits
#sdf
#dfgdfg
asdads sdfdsf [#burgers], [#rabbits] dsfsdfds [#sdf] [#dfgdfg]
Updated Demo here
Another Example

Use a regular expression: \#\w*
string pattern = "\#\w*";
Regex rgx = new Regex(pattern, RegexOptions.IgnoreCase);
MatchCollection matches = rgx.Matches(input);

search string for everything before a set of characters in C#

I'm looking for a way to search a string for everything before a set of characters in C#. For Example, if this is my string value:
This is is a test.... 12345
I want build a new string with all of the characters before "12345".
So my new string would equal "This is is a test.... "
Is there a way to do this?
I've found Regex examples where you can focus on one character but not a sequence of characters.

You don't need to use a Regex:
public string GetBitBefore(string text, string end)
{
var index = text.IndexOf(end);
if (index == -1) return text;
return text.Substring(0, index);
}

You can use a lazy quantifier to match anything, followed by a lookahead:
var match = Regex.Match("This is is a test.... 12345", #".*?(?=\d{5})");
where:
.*? lazily matches everything (up to the lookahead)
(?=…) is a positive lookahead: the pattern must be matched, but is not included in the result
\d{5} matches exactly five digits. I'm assuming this is your lookahead; you can replace it

You can do so with help of regex lookahead.
.*(?=12345)
Example:
var data = "This is is a test.... 12345";
var rxStr = ".*(?=12345)";
var rx = new System.Text.RegularExpressions.Regex (rxStr,
System.Text.RegularExpressions.RegexOptions.IgnoreCase);
var match = rx.Match(data);
if (match.Success) {
Console.WriteLine (match.Value);
}
Above code snippet will print every thing upto 12345:
This is is a test....
For more detail about see regex positive lookahead

This should get you started:
var reg = new Regex("^(.+)12345$");
var match = reg.Match("This is is a test.... 12345");
var group = match.Groups[1]; // This is is a test....
Of course you'd want to do some additional validation, but this is the basic idea.

^ means start of string
$ means end of string
The asterisk tells the engine to attempt to match the preceding token zero or more times. The plus tells the engine to attempt to match the preceding token once or more
{min,max} indicate the minimum/maximum number of matches.
\d matches a single character that is a digit, \w matches a "word character" (alphanumeric characters plus underscore), and \s matches a whitespace character (includes tabs and line breaks).
[^a] means not so exclude a
The dot matches a single character, except line break characters
In your case there many way to accomplish the task.
Eg excluding digit: ^[^\d]*
If you know the set of characters and they are not only digit, don't use regex but IndexOf(). If you know the separator between first and second part as "..." you can use Split()

Take a look at this snippet:
class Program
{
static void Main(string[] args)
{
string input = "This is is a test.... 12345";
// Here we call Regex.Match.
MatchCollection matches = Regex.Matches(input, #"(?<MySentence>(\w+\s*)*)(?<MyNumberPart>\d*)");
foreach (Match item in matches)
{
Console.WriteLine(item.Groups["MySentence"]);
Console.WriteLine("******");
Console.WriteLine(item.Groups["MyNumberPart"]);
}
Console.ReadKey();
}
}

You could just split, not as optimal as the indexOf solution
string value = "oiasjdoiasj12345";
string end = "12345";
string result = value.Split(new string[] { end }, StringSplitOptions.None)[0] //Take first part of the result, not the quickest but fairly simple

Regex help for this expression with digits wanted

I am splitting given text wherever eachDELETEDDELETED occours, however some of my files contain text like:
each2,DELETED6,DELETED
eachDELETED2,DELETED
each5,DELETED15,DELETED
each5,DELETED5,DELETED2
I want to do a regex replace and turn these expressions into eachDELETEDDELETED.
I have tried using the follow code:
Regex ra = new Regex(#"eachDELETED\d, DELETED");
MatchCollection mcMatches = ra.Matches(extracted);
foreach (Match m in mcMatches)
{
if (m.Success)
{
// MessageBox.Show(m.Value.ToString());
richTextBox5.Text += "JJJJ------>" +m.Value + "\n";
}
}
But I'm not getting any matches.

The regex each\d*,*DELETED\d*,DELETED\d* matches all the sample data:
each2,DELETED6,DELETED
eachDELETED2,DELETED
each5,DELETED15,DELETED
each5,DELETED5,DELETED2
If the lack of the comma in the second line is a typo, use each\d*,DELETED\d*,DELETED\d*
Basically, \d matches a digit and * means zero or more times.

Regex match between two strings that might contain another string

I'm doing a regex that is trying to match the following string:
.\SQL2012
From the two strings (they are contained within another larger string but that is irrelevant in this case):
/SERVER "\".\SQL2012\""
/SERVER .\SQL2012
So the "\" before and the \"" after the match may both be omitted in some cases. The regex I've come up with (from a previous question here on StackOverflow) is the following:
(?<=\/SERVER\s*(?:[""\\""]+)?)\w+(?=(?:[\\""""]+|$)| )
Which works fine if I'm trying to match TEST_SERVER instead of .\SQL2012 (because \w does not match special characters). Is there a way to match anything until \"" or a whitespace occurs?
I'm doing this in C#, here's my code:
string input = "/SERVER \"\\\".\\SQL2012\\\"\"";
string pattern = #"(?<=\/SERVER\s*(?:[""\\""]+)?)\w+(?=(?:[\\""""]+|$)| )";
Regex regEx = new Regex(pattern);
MatchCollection matches = regEx.Matches(input);
foreach (Match match in matches)
{
Console.WriteLine(match.ToString());
}
Console.ReadKey();

Add a word boundary \b just before to the lookahead,
string input = "/SERVER .\\SQL2012";
Regex rgx = new Regex(#"(?<=\/SERVER\s+""\\"").*?\b(?=\\""""|$| )|(?<=\/SERVER\s+).*?\b(?= |$)");
foreach (Match m in rgx.Matches(input))
Console.WriteLine(m.Groups[0].Value);
Console.WriteLine(input);
IDEONE

Regex to match and return group names

I need to match the following strings and returns the values as groups:
abctic
abctac
xyztic
xyztac
ghhtic
ghhtac
Pattern is wrote with grouping is as follows:
(?<arch>[abc,xyz,ghh])(?<flavor>[tic,tac]$)
The above returns only parts of group names. (meaning match is not correct).
If I use * in each sub pattern instead of $ at the end, groups are correct, but that would mean that abcticff will also match.
Please let me know what my correct regex should be.

Your pattern is incorrect because a pipe symbol | is used to specify alternate matches, not a comma in brackets as you were using, i.e., [x,y].
Your pattern should be: ^(?<arch>abc|xyz|ghh)(?<flavor>tic|tac)$
The ^ and $ metacharacters ensures the string matches from start to end. If you need to match text in a larger string you could replace them with \b to match on a word boundary.
Try this approach:
string[] inputs = { "abctic", "abctac", "xyztic", "xyztac", "ghhtic", "ghhtac" };
string pattern = #"^(?<arch>abc|xyz|ghh)(?<flavor>tic|tac)$";
foreach (var input in inputs)
{
var match = Regex.Match(input, pattern);
if (match.Success)
{
Console.WriteLine("Arch: {0} - Flavor: {1}",
match.Groups["arch"].Value,
match.Groups["flavor"].Value);
}
else
Console.WriteLine("No match for: " + input);
}