I want to check if a String s, contains "a" or "b" or "c", in C#. I am looking for a nicer solution than using
if (s.contains("a")||s.contains("b")||s.contains("c"))
This question is related to
c#
static void Main(string[] args)
{
string illegalCharacters = "!@#$%^&*()\\/{}|<>,.~`?"; //We'll call these the bad guys
string goodUserName = "John Wesson"; //This is a good guy. We know it. We can see it!
//But what if we want the program to make sure?
string badUserName = "*_Wesson*_John!?"; //We can see this has one of the bad guys. Underscores not restricted.
Console.WriteLine("goodUserName " + goodUserName +
(!HasWantedCharacters(goodUserName, illegalCharacters) ?
" contains no illegal characters and is valid" : //This line is the expected result
" contains one or more illegal characters and is invalid"));
string captured = "";
Console.WriteLine("badUserName " + badUserName +
(!HasWantedCharacters(badUserName, illegalCharacters, out captured) ?
" contains no illegal characters and is valid" :
//We can expect this line to print and show us the bad ones
" is invalid and contains the following illegal characters: " + captured));
}
//Takes a string to check for the presence of one or more of the wanted characters within a string
//As soon as one of the wanted characters is encountered, return true
//This is useful if a character is required, but NOT if a specific frequency is needed
//ie. you wouldn't use this to validate an email address
//but could use it to make sure a username is only alphanumeric
static bool HasWantedCharacters(string source, string wantedCharacters)
{
foreach(char s in source) //One by one, loop through the characters in source
{
foreach(char c in wantedCharacters) //One by one, loop through the wanted characters
{
if (c == s) //Is the current illegalChar here in the string?
return true;
}
}
return false;
}
//Overloaded version of HasWantedCharacters
//Checks to see if any one of the wantedCharacters is contained within the source string
//string source ~ String to test
//string wantedCharacters ~ string of characters to check for
static bool HasWantedCharacters(string source, string wantedCharacters, out string capturedCharacters)
{
capturedCharacters = ""; //Haven't found any wanted characters yet
foreach(char s in source)
{
foreach(char c in wantedCharacters) //Is the current illegalChar here in the string?
{
if(c == s)
{
if(!capturedCharacters.Contains(c.ToString()))
capturedCharacters += c.ToString(); //Send these characters to whoever's asking
}
}
}
if (capturedCharacters.Length > 0)
return true;
else
return false;
}
Well, there's always this:
public static bool ContainsAny(this string haystack, params string[] needles)
{
foreach (string needle in needles)
{
if (haystack.Contains(needle))
return true;
}
return false;
}
Usage:
bool anyLuck = s.ContainsAny("a", "b", "c");
Nothing's going to match the performance of your chain of ||
comparisons, however.
Here's a LINQ solution which is virtually the same but more scalable:
new[] { "a", "b", "c" }.Any(c => s.Contains(c))
As a string is a collection of characters, you can use LINQ extension methods on them:
if (s.Any(c => c == 'a' || c == 'b' || c == 'c')) ...
This will scan the string once and stop at the first occurance, instead of scanning the string once for each character until a match is found.
This can also be used for any expression you like, for example checking for a range of characters:
if (s.Any(c => c >= 'a' && c <= 'c')) ...
If you're looking for arbitrary strings, and not just characters, you can use an overload of IndexOfAny which takes string arguments from the new project NLib:
if (s.IndexOfAny("aaa", "bbb", "ccc", StringComparison.Ordinal) >= 0)
// Nice method's name, @Dan Tao
public static bool ContainsAny(this string value, params string[] params)
{
return params.Any(p => value.Compare(p) > 0);
// or
return params.Any(p => value.Contains(p));
}
Any
for any, All
for every
public static bool ContainsAny(this string haystack, IEnumerable<string> needles)
{
return needles.Any(haystack.Contains);
}
If you need ContainsAny with a specific StringComparison
(for example to ignore case) then you can use this String Extentions method.
public static class StringExtensions
{
public static bool ContainsAny(this string input, IEnumerable<string> containsKeywords, StringComparison comparisonType)
{
return containsKeywords.Any(keyword => input.IndexOf(keyword, comparisonType) >= 0);
}
}
Usage with StringComparison.CurrentCultureIgnoreCase
:
var input = "My STRING contains Many Substrings";
var substrings = new[] {"string", "many substrings", "not containing this string" };
input.ContainsAny(substrings, StringComparison.CurrentCultureIgnoreCase);
// The statement above returns true.
”xyz”.ContainsAny(substrings, StringComparison.CurrentCultureIgnoreCase);
// This statement returns false.
You can try with regular expression
string s;
Regex r = new Regex ("a|b|c");
bool containsAny = r.IsMatch (s);
var values = new [] {"abc", "def", "ghj"};
var str = "abcedasdkljre";
values.Any(str.Contains);
List<string> includedWords = new List<string>() { "a", "b", "c" };
bool string_contains_words = includedWords.Exists(o => s.Contains(o));
This is a "nicer solution" and quite simple
if(new string[] { "A", "B", ... }.Any(s=>myString.Contains(s)))
You can use Regular Expressions
if(System.Text.RegularExpressions.IsMatch("a|b|c"))
Source: Stackoverflow.com