Looking for help where given any string, return a string with alphanumeric characters only and replace all non-alphanumeric characters with _
so string "ASD@#$123" becomes "ASD___123"
etc
thanks
2
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return txt.Where(Char.IsLetterOrDigit).ToArray()) shrinks the string, still thinking of how to replace them :)Kumar– Kumar2012-05-15 19:01:34 +00:00Commented May 15, 2012 at 19:01
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possible duplicate of Replace all Special Characters in a string IN C#Pranay Rana– Pranay Rana2012-05-15 19:07:25 +00:00Commented May 15, 2012 at 19:07
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3 Answers
For most string operations, you would be better off (in terms of both efficiency and conciseness) if you use regular expressions rather than LINQ:
string input = "ASD@#$123";
string result = Regex.Replace(input, "[^A-Z0-9]", "_", RegexOptions.IgnoreCase);
If you want to preserve any Unicode alphanumeric character, including non-ASCII letters such as é, we can use the non-word character class to make it even simpler:
string input = "ASD@#$123";
string result = Regex.Replace(input, @"\W", "_");
For the sake of comparison, here is the same conversion done using LINQ (allowing just ASCII letters and digits):
string input = "ASD@#$123";
string result =
new string(input.Select(c =>
c >= 'A' && c <= 'Z' || c >= 'a' && c <= 'z' || c >= '0' && c <= '9' ? c : '_'
).ToArray());
Or, if Char.IsLetterOrDigit meets your requirements:
string input = "ASD@#$123";
string result =
new string(input.Select(c => char.IsLetterOrDigit(c) ? c : '_').ToArray());
Note that Char.IsLetterOrDigit will allow non-ASCII letters, and is comparable to the \w word character class whose negation was used in our second example.
Edit: As Steve Wortham has observed, the LINQ versions are actually more than 3× faster than the regex (even when a Regex instance is created in advance with RegexOptions.Compiled and re-used).
7 Comments
L.B
Ö or α ,for ex, are alphanumeric chars :)
Douglas
@L.B: Since this is a redaction operation, it’s more reasonable to assume that non-ASCII characters are not permitted (although I made a note to that effect at the end).
Douglas
@L.B: For the sake of clarity, I’ve added another example which preserves Unicode letters.
Steve Wortham
+1. Although I must note that even though your first Regex solution is concise, it is over 3 times slower than your Linq solutions. It helps somewhat to enable RegexOptions.Compiled, but Linq still wins the race easily.
Douglas
@SteveWortham: Strange… Let me test it out on my end.
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char[] unwanted = new[] {'@', '#', '$'};
foreach(var x in query)
{
x.SomePropertyName = string.Join("_", x.SomePropertyName.Split(unwanted));
};
LINQ lambda expression to replace multiple characters in a string
Comments
Here is the function for you:
String ReplaceWrongChars(String baseString)
{
Regex rx = new Regex("[^A-Za-z0-9 ]", RegexOptions.CultureInvariant);
String rv = rx.Replace(baseString, "_");
return rv;
}
If you do not need spaces included, use "[^A-Za-z0-9]" as regular expression.
