I have the following regex ^[a-zA-Z0-9]+$ which would allow alpha numeric characters. The problem here is that if I enter only numeric character like "897687", then the regex still matches. I don't want that to happen. There should be at least one text character and it should start with a text character. For example like "a343" or "a98bder" or "a4544fgf343"
It would be great if you could help me to improve my regex for this.
Sounds like you want:
^[a-zA-Z][a-zA-Z0-9]*$
EXPLANATION
^ asserts position at the start of a line
Match a single character present in the list below [a-zA-Z]
» a-z a single character in the range between a (index 97) and z (index 122) (case sensitive)
» A-Z a single character in the range between A (index 65) and Z (index 90) (case sensitive)
Match a single character present in the list below [a-zA-Z0-9]*
* Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
a-z a single character in the range between a (index 97) and z (index 122) (case sensitive)
A-Z a single character in the range between A (index 65) and Z (index 90) (case sensitive)
0-9 a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
$ asserts position at the end of a line
+ for 1 or more to make sure you get at least one cookie ;)Just in case that the ASCII characters are at some point not enough, here the Unicode version:
^\p{L}[\p{L}\p{N}]*$
\p{L} is any Unicode code point that has the property letter ==> Any letter from any language (that is in Unicode)
\p{N} is any Unicode code point that has the property number ==> Any number character from any language (that is in Unicode)
This function will return true or false based on whether the Regular Expression is matched or not,
public static Boolean isAlphaNumeric(string strToCheck)
{
Regex rg = new Regex(@"^[a-zA-Z0-9\s,]*$");
return rg.IsMatch(strToCheck);
}
^[a-zA-Z][a-zA-Z0-9]*$
Should do the trick!
Alternatively, if you wish to include all alphanumeric plus an underscore you can use:
^[a-zA-Z][\w]*$
\w. In .net it is [\p{L}\p{N}_] it includes all Unicode letters, numbers and (at least) the underscore.
Or slightly less verbose than the accepted answer:
^[a-zA-Z][\w]*$
C# regex has character class indicator "\w" for alphanumeric characters, but does not have a character class for just alphabetic (no digits), hence you have to specify class set [a-zA-Z] manually.
This is the best solution to check alphanumeric,
if it is alphanumeric -"Success".
if (System.Text.RegularExpressions.Regex.IsMatch(txt.Text, @"[a-zA-Z]") &&
System.Text.RegularExpressions.Regex.IsMatch(txt.Text, @"[0-9]")
{
// Success - It is alphanumric
}
else
{
// Error - It is not alphanumric
}
Because I don't see it mentioned in the other answers – you can set an in-line flag to make the pattern case-insensitive:
(?i)^[a-z][a-z0-9]+$
And, regarding _ being included in \w, you can exclude certain characters from character ranges:
(?i)^[a-z][\w-[_]]+$
However, this is harder to read and it's not like it makes the pattern any shorter.
More importantly, if the regex options don't include the ECMAScript enum (it doesn't by default), \w will match letters beyond a-z & A-Z – such as accented letters, letters in other languages, etc.
In any case, it's always nice to know about all the options available to you.
