Password Validator in C#

karthik v

15y2.4k.NET

Hi Experts
I have a case where i need to validate the password for the following cases
1) at least one lower case letter
2) at least one upper case letter
3) at least special character
4) at least one number

In the above conditions if any of the three conditions are satisfied then the password is okay .

Can any one help me with this issue?

5 Replies

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Vulpes15y ago
Accepted answer
It's difficult for regular expressions to deal with stuff such as 'any three out four of conditions' using expressions of a reasonable length and you'd need alternators for each of the lookaheads in Jitendra's expression to do it properly.

If you don't need to do it using reglar expressions, then I'd do it using traditional string parsing which is relatively straightforward to do and executes quickly. I've assumed below that it's no problem if all four conditions are satisfied and not just any three:

using System;

class Test
{
static void Main()
{
string[] passWords = {"aX2#", "sed2T", "*v3X", "Ae234&B", "fg234", "g1HL","#1$23", "5a7%"};

foreach(string passWord in passWords)
{
bool b = ValidatePassword(passWord);
Console.WriteLine("'{0}' is{1} a valid password", passWord, b ? "": "n't");
}

Console.ReadKey();
}

static bool ValidatePassword(string passWord)
{
int validConditions = 0;

foreach(char c in passWord)
{
if (c >= 'a' && c <= 'z')
{
validConditions++;
break;
}
}

foreach(char c in passWord)
{
if (c >= 'A' && c <= 'Z')
{
validConditions++;
break;
}
}

if (validConditions == 0) return false;

foreach(char c in passWord)
{
if (c >= '0' && c <= '9')
{
validConditions++;
break;
}
}

if (validConditions == 1) return false;

if(validConditions == 2)
{
char[] special = {'@', '#', '$', '%', '^', '&', '+', '='}; // or whatever

if (passWord.IndexOfAny(special) == -1) return false;
}

return true;
}
}
0
Vulpes15y ago
Like us all, I have my strengths and weaknesses but anything to do with strings is definitely a strength :)
0
Jiteendra Sampathirao15y ago
@vulpes: you are great...
0
karthik v15y ago
Thank you the quick response guys.I used the C# code and that worked well.I tried to use the regex but it was a kind of complicating things.Thank you so much guys...
0
Jiteendra Sampathirao15y ago
Hi,
try this..

ValidationExpression="^.*(?=.{10,})(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%^&+=]).*$"
ControlToValidate="TextBox1">

hope this help you...
0