.NET Regular Expression to match any kind of letter from any language

You can use Char.IsLetter:

Indicates whether the specified Unicode character is categorized as a Unicode letter.

With .Net 4.0:

string onlyLetters = String.Concat(str.Where(Char.IsLetter)); 

On 3.5 String.Concat only excepts an array, so you should also call ToArray.

\p{L}* should match "any kind of letter from any language". It should work, I used it in a i18n-proof uppercase/lowercase recognition regex in .NET.

Your problem is more likely to the fact that you will only have to have one alpha-char, because the regex will match anything that has at least one char.

By adding ^ as prefix and $ as postfix, the whole sentence should comply to your regex. So this prob works:

^\p{L}*$ 

Regexbuddy explains:

1. ^ Assert position at beginning of the string
2. \p{L} A character with the Unicode property 'letter' (any kind of letter from any kind of language) 2a. Between zero and unlimited times, as many as possible (greedy)
3. $ Assert position at the end of the string

I’ve just had to validate a URL and I chose this regular expression in .NET.

^[(\p{L})?(\p{M})?-]*$ 

Begin and end with a character of any language (optionally either letters or marks) and allow hyphens.

\w - matches any alphanumeric character (including numbers)

In my tests it has matched:

• ã
• à
• ç
• 8
• z

and hasn't matched:

• ;
• ,
• \
• :

In case you know exactly what you want to exclude (like a little list) you cand do the following:

[^;,\`.]

which matches one time any character that isnt:

• ;
• ,
• \
• `
• .

Hope it helps!