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I need a regular expression to check that a string contains combination of alphabets and numbers.Special characters and space is not allowed.my string should contain atleast one character and one alphabet

neethu
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    Have you tried anything? I think regular expressions are pretty good covered with tutorials and examples, maybe you should use a search engine... – Matten May 01 '13 at 08:30
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    Can you elaborate on your question? This is quite a bit vague... http://gskinner.com/RegExr/ might be a start for you ;) – Ken de Jong May 01 '13 at 08:31
  • Possible Duplicate of [Regular Expression for alphanumeric and underscores](http://stackoverflow.com/q/336210/781965) – Jeff May 01 '13 at 08:33
  • my string should contain atleast one character and one alphabet – neethu May 01 '13 at 08:47
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    That's something you should mention in your question, not just in a comment. Not everyone reads those. Also, define "alphabets" and "numbers". Does `ä` count? – Tim Pietzcker May 01 '13 at 09:43
  • What do you mean by `one character and one alphabet`? – Toto May 01 '13 at 10:19

3 Answers3

4

Description

This will

  • find all strings which have at least one letter and one number
  • and only contain letters and numbers in any order

^(?=[^\s]*?[0-9])(?=[^\s]*?[a-zA-Z])[a-zA-Z0-9]*$

enter image description here

Example

Note for some of these examples I have removed the $ at the end of the expression as source string in the example really contains many lines. To properly validate the string you'll need to remove the multiline matching and use the $ character as shown above.

Live Example

Sample Text

11
22
33
1
2
3
1a
2b
3c
a1
b2
c3
1a1a
2b2b
3b3b
1a1
2b2
3b3
a1a
b2b
c3c
a
b
c
aa
bb
cc

C# Code Example

using System;
using System.Text.RegularExpressions;
namespace myapp
{
  class Class1
    {
      static void Main(string[] args)
        {
          String sourcestring = "source string to match with pattern";
          Regex re = new Regex(@"^(?=[^\s]*?[0-9])(?=[^\s]*?[a-zA-Z])[a-zA-Z0-9]*",RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace | RegexOptions.Multiline | RegexOptions.Singleline);
          MatchCollection mc = re.Matches(sourcestring);
          int mIdx=0;
          foreach (Match m in mc)
           {
            for (int gIdx = 0; gIdx < m.Groups.Count; gIdx++)
              {
                Console.WriteLine("[{0}][{1}] = {2}", mIdx, re.GetGroupNames()[gIdx], m.Groups[gIdx].Value);
              }
            mIdx++;
          }
        }
    }
}

Matches Found

[0][0] = 1a
[1][0] = 2b
[2][0] = 3c
[3][0] = a1
[4][0] = b2
[5][0] = c3
[6][0] = 1a1a
[7][0] = 2b2b
[8][0] = 3b3b
[9][0] = 1a1
[10][0] = 2b2
[11][0] = 3b3
[12][0] = a1a
[13][0] = b2b
[14][0] = c3c

Summary

This works because the expression looks ahead to validate it can indeed find a number and a letter in the string, then matches all letters and numbers

animuson
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Ro Yo Mi
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3

In order to be unicode compatible:

^[\pL\pN]+$

\pL stands for any letter
\pN stands for any digit

Toto
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2

To match just a single 0-9 or a-z or A-Z.

[0-9a-zA-Z]

To match 1 or more 

[0-9a-zA-Z]\+

And if you are interested in the entire line being alphanumeric characters.

^[0-9a-zA-Z]\+$

The ^ matches the beginning of the line and the $ matches the end of the line.

Megasaur
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