i want to allow only alphanumeric password i have written following code to match the same
but the same is not working
Regex.IsMatch(txtpassword.Text, "^[a-zA-Z0-9_]*$") never return false
even if i type password test(which do not contain any number).
ElseIf Regex.IsMatch(txtpassword.Text, "^[a-zA-Z0-9_]*$") = False Then
div_msg.Attributes.Add("class", "err-msg")
lblmsg.Text = "password is incorrect"
I have tried this also
Dim r As New Regex("^[a-zA-Z0-9]+$")
Dim bool As Boolean
bool = r.IsMatch(txtpassword.Text) and for txtpassword.Text = '4444' , bool is coming true i dont know what is wrong.
First of all, the '_' is not a valid alpha-numeric character.
See http://en.wikipedia.org/wiki/Alphanumeric
And, second, take another look at your regular expression.
[a-zA-Z0-9_]*
This can match 0 OR more alpha-numeric characters or 0 OR more '_' characters.
Using this pattern, a password '&#&#^$' would return TRUE.
You probably want to test for 1 OR more characters that ARE NOT an alpha-numeric. If that test returns TRUE, then throw the error.
Hope this helps.
Try the following Expression:
([^a-zA-Z0-9]+)
This will match if your Password contains any character that is not alphanumeric.
If you get a match, do your error handling.
So based on the Regex that you have in the question, it appears you want a password with one lower-case and upper-case letter, one number, and an _; so here is a Regex that will do that:
(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*_).{4,8}
Debuggex Demo
The {4,8} indicates the length of the password; you can set that accordingly.
Related
I have a textbox that user enter a string into it.
<td class ="auto-style2" > <asp:TextBox ID="TextBox_PassportCode" runat="server" Width ="100%"></asp:TextBox></td>
and:
string code=TextBox_PassportCode.text;
I want to check if "code" contain alphabet + digit together. Eg,A1234 or 1234A Or fhg21564,
It is not important how many alphabet or how many digit user enter, but textbox should contain alphabet and digit.
Try doing like below. Since you said the text could be either A1234 or 1234A; it not necessary that string starts with alphabet. In which case, you can check against regular expression [a-zA-Z0-9]+ which will match combination of 1 or more alphabet + digits. See MSDN on how to use
string code=TextBox_PassportCode.text;
string pat = "[a-zA-Z0-9]+";
if (System.Text.RegularExpressions.Regex.IsMatch(code, pat, System.Text.RegularExpressions.RegexOptions.IgnoreCase))
{
System.Console.WriteLine("Match Found");
}
else
{
System.Console.WriteLine("No Match");
}
Use a regular expression for this.
See this answer.
C# Regex to allow only alpha numeric
I would like to use the grepl function in R to find if a string contains something, but on the condition that it is not preceeded by something else.
So for example say I wanted to find a string which includes the pattern 'xx', as long as it is not preceeded by 'yy'. So:
'123xx45' world return TRUE
'123yy4xx5' would also return TRUE as the 'yy' is not immediately preceding 'xx'
However '123yyxx45' would return FALSE.
Please let me know if anything is unclear or you would like a better example.
How about grepl('(?<!yy)xx', c('123yy4xx5','123xx45','123yyxx45'), perl=TRUE)?
your.data <- c('123yy4xx5','123xx45','123yyxx45')
grepl("xx",your.data) & !grepl("yyxx",your.data)
[1] TRUE TRUE FALSE
i need a regular expression validation for
numeric digits grouped as X-XXXXX-XXX-X
can any one help?
Regex reg = new Regex("\b[0-9]\-[0-9]{5}\-[0-9]{3}\-[0-9]\b");
Here is what I use for checking social security numbers that user's input:
Public Shared Function CheckSSNFormat(ByVal text As String) As Boolean
Dim digits As String = Regex.Replace(text, "[^0-9]", "")
Return digits.Length = 9
End Function
It doesn't check that they are input in a specific format, but that might be better depending on what you really need -- so just thought I'd give you another option, just incase.
The above just removes everything except digits, and returns true if there are 9 digits (a valid SS#). It does mean some goofy user could enter something like: hello123456789 and it would accept it as valid, but that is fine for me, and I'd rather do that than not accept 123456789 just because I was looking for 123-45-6789 only.
Later I use this to save to my database:
Public Shared Function FormatSSNForSaving(ByVal text As String) As String
If text = "" Then text = "000-00-0000"
Return Regex.Replace(text, "[^0-9]", "")
End Function
and this anytime I want to display the value (actually I use this one for phone numbers, turns out I never display the SS# so don't have a function for it):
Public Shared Function FormatPhoneForDisplay(ByVal text As String) As String
If text.Length <> 10 Then Return text
Return "(" & text.Substring(0, 3) & ") " & text.Substring(3, 3) & "-" & text.Substring(6, 4)
End Function
(^\d{1}-\d{5}-\d{3}-\d{1}$), this should do.
[0-9]-[0-9]{5}-[0-9]{3}-[0-9]
you could also use round brackets to extract the numbers if you want:
([0-9])-([0-9]{5})-([0-9]{3})-([0-9])
and get the values with $1 $2 etc. in the Regex.Replace() function
Regex pattern = new Regex("\b\d-\d{5}-\d{3}-\d\b");
\b - word boundary
\d - digit
I am trying to write a regular expression that doesn't allow single or double quotes in a string (could be single line or multiline string). Based on my last question, I wrote like this ^(?:(?!"|').)*$, but it is not working. Really appreciate if anybody could help me out here.
Just use a character class that excludes quotes:
^[^'"]*$
(Within the [] character class specifier, the ^ prefix inverts the specification, so [^'"] means any character that isn't a ' or ".)
Just use a regex that matches for quotes, and then negate the match result:
var regex = new Regex("\"|'");
bool noQuotes = !regex.IsMatch("My string without quotes");
Try this:
string myStr = "foo'baa";
bool HasQuotes = myStr.Contains("'") || myStr.Contains("\""); //faster solution , I think.
bool HasQuotes2 = Regex.IsMatch(myStr, "['\"]");
if (!HasQuotes)
{
//not has quotes..
}
This regular expression below, allows alphanumeric and all special characters except quotes(' and "")
#"^[a-zA-Z-0-9~+:;,/#&_#*%$!()\[\] ]*$"
You can use it like
[RegularExpression(#"^[a-zA-Z-0-9~+:;,/#&_#*%$!()**\[\]** ]*$", ErrorMessage = "Should not allow quotes")]
here use escape sequence() for []. Since its not showing in this post
I've used both of the following Regular Expressions for testing for a valid email expression with ASP.NET validation controls. I was wondering which is the better expression from a performance standpoint, or if someone has better one.
- \w+([-+.']\w+)*#\w+([-.]\w+)*\.\w+([-.]\w+)*
- ^([0-9a-zA-Z]([-\.\w]*[0-9a-zA-Z])*#([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,9})$
I'm trying avoid the "exponentially slow expression" problem described on the BCL Team Blog.
UPDATE
Based on feedback I ended up creating a function to test if an email is valid:
Public Function IsValidEmail(ByVal emailString As String, Optional ByVal isRequired As Boolean = False) As Boolean
Dim emailSplit As String()
Dim isValid As Boolean = True
Dim localPart As String = String.Empty
Dim domainPart As String = String.Empty
Dim domainSplit As String()
Dim tld As String
If emailString.Length >= 80 Then
isValid = False
ElseIf emailString.Length > 0 And emailString.Length < 6 Then
'Email is too short
isValid = False
ElseIf emailString.Length > 0 Then
'Email is optional, only test value if provided
emailSplit = emailString.Split(CChar("#"))
If emailSplit.Count <> 2 Then
'Only 1 # should exist
isValid = False
Else
localPart = emailSplit(0)
domainPart = emailSplit(1)
End If
If isValid = False OrElse domainPart.Contains(".") = False Then
'Needs at least 1 period after #
isValid = False
Else
'Test Local-Part Length and Characters
If localPart.Length > 64 OrElse ValidateString(localPart, ValidateTests.EmailLocalPartSafeChars) = False OrElse _
localPart.StartsWith(".") OrElse localPart.EndsWith(".") OrElse localPart.Contains("..") Then
isValid = False
End If
'Validate Domain Name Portion of email address
If isValid = False OrElse _
ValidateString(domainPart, ValidateTests.HostNameChars) = False OrElse _
domainPart.StartsWith("-") OrElse domainPart.StartsWith(".") OrElse domainPart.Contains("..") Then
isValid = False
Else
domainSplit = domainPart.Split(CChar("."))
tld = domainSplit(UBound(domainSplit))
' Top Level Domains must be at least two characters
If tld.Length < 2 Then
isValid = False
End If
End If
End If
Else
'If no value is passed review if required
If isRequired = True Then
isValid = False
Else
isValid = True
End If
End If
Return isValid
End Function
Notes:
IsValidEmail is more restrictive about characters allowed then the RFC, but it doesn't test for all possible invalid uses of those characters
If you're wondering why this question is generating so little activity, it's because there are so many other issues that should be dealt with before you start thinking about performance. Foremost among those is whether you should be using regexes to validate email addresses at all--and the consensus is that you should not. It's much trickier than most people expect, and probably pointless anyway.
Another problem is that your two regexes vary hugely in the kinds of strings they can match. For example, the second one is anchored at both ends, but the first isn't; it would match ">>>>foo#bar.com<<<<" because there's something that looks like an email address embedded in it. Maybe the framework forces the regex to match the whole string, but if that's the case, why is the second one anchored?
Another difference is that the first regex uses \w throughout, while the second uses [0-9a-zA-Z] in many places. In most regex flavors, \w matches the underscore in addition to letters and digits, but in some (including .NET) it also matches letters and digits from every writing system known to Unicode.
There are many other differences, but that's academic; neither of those regexes is very good. See here for a good discussion of the topic, and a much better regex.
Getting back to the original question, I don't see a performance problem with either of those regexes. Aside from the nested-quantifiers anti-pattern cited in that BCL blog entry, you should also watch out for situations where two or more adjacent parts of the regex can match the same set of characters--for example,
([A-Za-z]+|\w+)#
There's nothing like that in either of the regexes you posted. Parts that are controlled by quantifiers are always broken up by other parts that aren't quantified. Both regexes will experience some avoidable backtracking, but there are many better reasons than performance to reject them.
EDIT: So the second regex is subject to catastrophic backtracking; I should have tested it thoroughly before shooting my mouth off. Taking a closer look at that regex, I don't see why you need the outer asterisk in the first part:
[0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*
All that bit does is make sure the first and last characters are alphanumeric while allowing some additional characters in between. This version does the same thing, but it fails much more quickly when no match is possible:
[0-9a-zA-Z][-.\w]*[0-9a-zA-Z]
That would probably suffice to eliminate the backtracking problem, but you could also make the part after the "#" more efficient by using an atomic group:
(?>(?:[0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+)[a-zA-Z]{2,9}
In other words, if you've matched all you can of substrings that look like domain components with trailing dots, and the next part doesn't look like a TLD, don't bother backtracking. The first character you would have to give up is the final dot, and you know [a-zA-Z]{2,9} won't match that.
We use this RegEx which has been tested in-house against 1.5 million addresses. It correctly identifies better than 98% of ours, but there are some formats that I'm aware of that it would error on.
^([\w-]+(?:\.[\w-]+)*)#((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$
We also make sure that there are no EOL characters in the data since an EOL can fake out this RegEx. Our Function:
Public Function IsValidEmail(ByVal strEmail As String) As Boolean
' Check An eMail Address To Ensure That It Is Valid
Const cValidEmail = "^([\w-]+(?:\.[\w-]+)*)#((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$" ' 98% Of All Valid eMail Addresses
IsValidEmail = False
' Take Care Of Blanks, Nulls & EOLs
strEmail = Replace(Replace(Trim$(strEmail & " "), vbCr, ""), vbLf, "")
' Blank eMail Is Invalid
If strEmail = "" Then Exit Function
' RegEx Test The eMail Address
Dim regEx As New System.Text.RegularExpressions.Regex(cValidEmail)
IsValidEmail = regEx.IsMatch(strEmail)
End Function
I am a newbie, but I tried the following and it seemed to have limited the ".xxx" to only two occurrences or less, after the symbol '#'.
^([a-zA-Z0-9]+[a-zA-Z0-9._%-]*#(?:[a-zA-Z0-9-])+(\.+[a-zA-Z]{2,4}){1,2})$
Note: I had to substitute single '\' with double '\\' as I am using this reg expr in R.
These don't check for all allowable email addresses according to the email address RFC.
I let MS to do the work for me:
Public Function IsValidEmail(ByVal emailString As String) As Boolean
Dim retval As Boolean = True
Try
Dim address As New System.Net.Mail.MailAddress(emailString)
Catch ex As Exception
retval = False
End Try
Return retval
End Function
For server side validation, I found Phil Haack's solution to be one of the better ones. His attempt was to stick to the RFC:
string pattern = #"^(?!\.)(""([^""\r\\]|\\[""\r\\])*""|"
+ #"([-a-z0-9!#$%&'*+/=?^_`{|}~]|(?<!\.)\.)*)(?<!\.)"
+ #"#[a-z0-9][\w\.-]*[a-z0-9]\.[a-z][a-z\.]*[a-z]$";
Regex regex = new Regex(pattern, RegexOptions.IgnoreCase);
return regex.IsMatch(emailAddress);
Details:
http://blog.degree.no/2013/01/email-validation-finally-a-net-regular-expression-that-works/
Just to contribute, I am using this regex.
^([a-zA-Z0-9]+[a-zA-Z0-9._%-]*#(?:[a-zA-Z0-9-]+\.)+[a-zA-Z]{2,4})$
The thing about it is the specifications are changing with each domain extension that is introduced.
You sit here mod your regex, test, test, test, and more testing. You finally get what you "think" is accurate then the specification changes... You update your regex to account for what the new requirements are..
Then someone enters aa#aa.aa and you've done all that work for what? It walks through your fancy regex.. bummer!
You may as well just check for a single #, and a "." and move on. I assure you, you will not get someones email if they do not want to give it up. You'll get garbage or their hotmail account they never check and couldn't care less about.
I've seen in many cases this goes horribly wrong and a client calls up because their own email address is rejected because of a poorly crafted regex check. Which as mentioned shouldn't have even been attempted.
TextBox :-
<asp:TextBox ID="txtemail" runat="server" CssClass="form-control pantxt" Placeholder="Enter Email Address"></asp:TextBox>
Required Filed validator:
<asp:RequiredFieldValidator ID="RequiredFieldValidator9" runat="server" ControlToValidate="txtemail" ErrorMessage="Required"></asp:RequiredFieldValidator>
Regular Expression for email validation :
<asp:RegularExpressionValidator ID="validateemail" runat="server" ControlToValidate="txtemail" ValidationExpression="\w+([-+.']\w+)*#\w+([-.]\w+)*\.\w+([-.]\w+)*" ErrorMessage="Invalid Email"></asp:RegularExpressionValidator>
Use this regular expression for email validation in asp.net