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I want only matching string using regex

I have a string "myname 18-may 1234" and I want only "myname" from whole string using a regex.
I tried using the \b(^[a-zA-Z]*)\b regex and that gave me "myname" as a result.
But when the string changes to "1234 myname 18-may" the regex does not return "myname". Please suggest the correct way to select only "myname" whole word.
Is it also possible - given the string in
"1234 myname 18-may" format - to get myname only, not may?

UPDATE
Judging by your feedback to your other question you might need
(?<!\p{L})\p{L}+(?!\p{L})
ORIGINAL ANSWER
I have come up with a lighter regex that relies on the specific nature of your data (just a couple of words in the string, only one is whole word):
\b(?<!-)\p{L}+\b
See demo
Or even a more restrictive regex that finds a match only between (white)spaces and string start/end:
(?<=^|\s)\p{L}+(?=\s|$)
The following regex is context-dependent:
\p{L}+(?=\s+\d{1,2}-\p{L}{3}\b)
See demo
This will match only the word myname.
The regex means:
\p{L}+ - Match 1 or more Unicode letters...
(?=\s+\d{1,2}-\p{L}{3}\b) - until it finds 1 or more whitespaces (\s+) followed with 1 or 2 digits, followed with a hyphen and 3 Unicode letters (\p{L}{3}) which is a whole word (\b). This construction is a positive look-ahead that only checks if something can be found after the current position in the string, but it does not "consume" text.
Since the date may come before the string, you can add an alternation:
\p{L}+(?=[ ]+\d{1,2}-\p{L}{3}\b)|(?<=\d{1,2}-\p{L}{3}[ ]+)\p{L}+
See another demo
The (?<=\d{1,2}-\p{L}{3}\s+) is a look-behind that checks for the same thing (almost) as the look-ahead, but before the myname.

here is a solution without RegEx
string input = "myname 18-may 1234";
string result = input.Split(' ').Where(x => x.All(y => char.IsLetter(y))).FirstOrDefault();

Do a replace using this regex:
(\s*\d+\-.{3}\s*|\s*.{3}\-\d+\s*)|(\s*\d+\s*)
you will end up with just your name.
Demo

Regex in a string

I need some help on a problem.
In fact I search to check for an image type by the hexadecimal code.
string JpgHex = "FF-D8-FF-E0-xx-xx-4A-46-49-46-00";
Then I have a condition on
string.StartsWith(pngHex).
The problem is that the "x" characters presents in my "JpgHex" string can be whatever I want.
I think I need a regex to check that but I don't know how!!
Thanks a lot!

I'm not quite clear what exactly you want to do, but the dot '.' character represents any character in Regex.
So the regex "^FF-D8-FF-E0-..-..-4A-46-49-46-00" will probably do the trick. '^' = Start of input.
If you want to allow only hex chars you can use "^FF-D8-FF-E0-[0-9A-F]{2}-[0-9A-F]{2}-4A-46-49-46-00".

Like I said, I'd need a better idea of what pattern you need to match.
Here are some examples:
Regex rgx =
new Regex(#"^FF-D8-FF-E0-[a-zA-Z0-9]{2}-[a-zA-Z0-9]{2}-4A-46-49-46-00$");
rgx.IsMatch(pngHex); // is match will return a bool.
I use [a-zA-Z0-9]{2} to denote two instances of a character, caps or small or a number. So the above regex would match :
FF-D8-FF-E0-aa-zZ-4A-46-49-46-00
FF-D8-FF-E0-11-22-4A-46-49-46-00
.. etc
Based on your need change the regex accordingly so for capitals and numbers only you change to [A-Z0-9]. The {2} denotes two occurrences.
The ^ denotes the string should start with FF and $ means the string should end with 00.
Lets say you wanted to only match two numbers, so you would use \d{2}, the whole thing would look like this:
Regex rgx = new Regex(#"^FF-D8-FF-E0-\d{2}-\d{2}-4A-46-49-46-00$");
rgx.IsMatch(pngHex);
How do I know of these magical characters? Simple, there are docs everywhere. See this MSDN page for some basic regex patterns. This page shows some quantifiers, those are things like match one or more or match only one.
Cheat-sheets also come in handy.

A regex would help you; you can use the following tool to help you test and learn: -
http://derekslager.com/blog/posts/2007/09/a-better-dotnet-regular-expression-tester.ashx
I recommend you have a play because then you'll learn!
To simply match any character in place of the x, the following should work: -
"^FF-D8-FF-E0-..-..-4A-46-49-46-00$"
In C#, it would be something like this: -
var test = "FF-D8-FF-E0-AB-CD-4A-46-49-46-00";
var foo = new Regex("^FF-D8-FF-E0-..-..-4A-46-49-46-00$");
if (foo.IsMatch(test))
{
// Do magic
}
You will need to read up on regular expressions to understand some of the characters that may not look familiar, i.e. ^ and $. See http://www.regular-expressions.info/

What is wrong with my regex (simple)?

I am trying to make a regex that matches all occurrences of words that are at the start of a line and begin with #.
For example in:
#region #like
#hey
It would match #region and #hey.
This is what I have right now:
^#\w*
I apologize for posting this question. I'm sure it has a very simple answer, but I have been unable to find it. I admit that I am a regex noob.

What you've got should work, depending on what flags you pass for RegexOptions. You need to make sure you pass RegexOptions.Multiline:
var matches = Regex.Matches(input, #"^#\w*", RegexOptions.Multiline);
See the documentation I linked to above:
Multiline Multiline mode. Changes the meaning of ^ and $ so they match at the beginning and end, respectively, of any line, and not just the beginning and end of the entire string.

The regex looks fine, make sure you're using a verbatim string literal (# prefix) to define your regex, i.e. #"^#\w*" otherwise the backslash will be treated as an escape sequence.

Use this regex
^#.+?\b
.+ will ensure at least one character after # and \b indicates word boundry. ? adds non-greediness to the + operator so as to avoid matching whole string #region #like

How to check if a string starts and ends with specific strings?

I have a string like:
string str = "https://abce/MyTest";
I want to check if the particular string starts with https:// and ends with /MyTest.
How can I acheive that?

This regular expression:
^https://.*/MyTest$
will do what you ask.
^ matches the beginning of the string.
https:// will match exactly that.
.* will match any number of characters (the * part) of any kind (the . part). If you want to make sure there is at least one character in the middle, use .+ instead.
/MyTest matches exactly that.
$ matches the end of the string.
To verify the match, use:
Regex.IsMatch(str, #"^https://.*/MyTest$");
More info at the MSDN Regex page.

Try the following:
var str = "https://abce/MyTest";
var match = Regex.IsMatch(str, "^https://.+/MyTest$");
The ^ identifier matches the start of the string, while the $ identifier matches the end of the string. The .+ bit simply means any sequence of chars (except a null sequence).
You need to import the System.Text.RegularExpressions namespace for this, of course.

I want to check if the particular string starts with "https://" and ends with "/MyTest".
Well, you could use regex for that. But it's clearer (and probably quicker) to just say what you mean:
str.StartsWith("https://") && str.EndsWith("/MyTest")
You then don't have to worry about whether any of the characters in your match strings need escaping in regex. (For this example, they don't.)

In .NET:
^https://.*/MyTest$

Try Expresso, good for building .NET regexes and teaching you the syntax at the same time.

HAndy tool for genrating regular expressions
http://txt2re.com/

Matching an (easy??) regular expression using C#'s regex

Ok sorry this might seem like a dumb question but I cannot figure this thing out :
I am trying to parse a string and simply want to check whether it only contains the following characters : '0123456789dD+ '
I have tried many things but just can't get to figure out the right regex to use!
Regex oReg = new Regex(#"[\d dD+]+");
oReg.IsMatch("e4");
will return true even though e is not allowed...
I've tried many strings, including Regex("[1234567890 dD+]+")...
It always works on Regex Pal but not in C#...
Please advise and again i apologize this seems like a very silly question

Try this:
#"^[0-9dD+ ]+$"
The ^ and $ at the beginning and end signify the beginning and end of the input string respectively. Thus between the beginning and then end only the stated characters are allowed. In your example, the regex matches if the string contains one of the characters even if it contains other characters as well.
#comments: Thanks, I fixed the missing + and space.

Oops, you forgot the boundaries, try:
Regex oReg = new Regex(#"^[0-9dD +]+$");
oReg.IsMatch("e4");
^ matches the begining of the text stream, $ matches the end.

It is matching the 4; you need ^ and $ to terminate the regex if you want a full match for the entire string - i.e.
Regex re = new Regex(#"^[\d dD+]+$");
Console.WriteLine(re.IsMatch("e4"));
Console.WriteLine(re.IsMatch("4"));

This is because regular expressions can also match parts of the input, in this case it just matches the "4" of "e4". If you want to match a whole line, you have to surround the regex with "^" (matches line start) and "$" (matches line end).
So to make your example work, you have to write is as follows:
Regex oReg = new Regex(#"^[\d dD+]+$");
oReg.IsMatch("e4");

I believe it's returning True because it's finding the 4. Nothing in the regex excludes the letter e from the results.

Another option is to invert everything, so it matches on characters you don't want to allow:
Regex oReg = new Regex(#"[^0-9dD+]");
!oReg.IsMatch("e4");