Check For Special Characters without using Regex

Question

i m a newbie in C# code , i need help with validating special characters without using regex , can someone help me?

i m using this code ATM and want to make it works without regex

else if (Regex.IsMatch(textBox2.Text, "^[a-zA-Z ]+$")==false)
        {
            MessageBox.Show("Name may not contain any special characters");
        }

Thanks!

Regex has its cons, but this is one of the cases where it *may* be used effectively. — manojlds, May 27 '14 at 16:55
there are many ways to do this... something like foreach(char c in string s) {//and then check against a generic list or something.} — Nyra, May 27 '14 at 16:57

manojlds · Accepted Answer · 2014-05-27T17:05:52.500

2

The regex solution isn't really bad, but if Regex is prohibited, you can do the following:

textBox2.Text.All(Char.IsLetter);

Update:

Since you want (space) too:

textBox2.Text.All(c => Char.IsLetter(c) || c == ' ');

Note that Char.IsLetter will return true for any Unicode letter. A more strict version would be:

textBox2.Text.All(c => (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c == ' '));

You get the idea. Basically, we go through all the characters and see if it is in the A-Z or the a-z range or a space.

Needs using System.Linq;. The same can be achieved using a simple loop too.

edited May 27 '14 at 17:05

answered May 27 '14 at 16:58

manojlds

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[`char.IsLetter()`](http://msdn.microsoft.com/en-us/library/yyxz6h5w.aspx#remarksToggle) covers considerably more ground than the character class `[A-Za-z]` – Nicholas Carey May 27 '14 at 17:08
@NicholasCarey - Yes, I had updated to include the more strict version. Refresh :) – manojlds May 27 '14 at 17:09

score 2 · Answer 2 · answered May 27 '14 at 17:05

We'll, you can do that lots of different ways. For instance,

A positive test, using Linq makes things nice and declarative:

public bool isValid( string s )
{
  Func<char,bool> valid = c => { c == ' ' || ( c >= 'a' && c <= 'z' ) || ( c >= 'A' || c <= 'Z' ) } ;
  return s.All(valid) ;
}

Ditto for a negative test using Linq

public bool isInvalid( string s )
{
  Func<char,bool> valid = c => { c == ' ' || ( c >= 'a' && c <= 'z' ) || ( c >= 'A' || c <= 'Z' ) } ;
  return s.Any(!valid) ;
}

Linq won't necessarily be the fastest way to do this so you might to simply simply iterate over the string, old-school:

public bool isValid( string s )
{
  bool valid = true ;
  for ( int i = 0 ; valid  && i < s.Length ; ++i )
  {
    char c = s[i] ;
    valid = c == ' ' || ( c >= 'a' && c <= 'z' ) || ( c >= 'A' && c <= 'Z' ) ;
  }
    return valid ;
}

score 0 · Answer 3 · edited May 23 '17 at 11:50

0

You can probably loop through the string and compare the characters against ascii codes

How to get ASCII value of string in C#

Check if it's in the upper case and lower case ascii code ranges

edited May 23 '17 at 11:50

Community

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answered May 27 '14 at 16:58

TGH

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Check For Special Characters without using Regex

3 Answers3