How can I check if a string contains a character in C

Question

Is there a function I can apply to a string that will return true of false if a string contains a character    I have strings with one or more character options such as   var abc    s   var def    aB   var ghi    Sj     What I would like to do for example is have a function that would return true or false if the above contained a lower or upper case  s    if  def Somefunction  s      true        Also in C  do I need to check if something is true like this or could I just remove the     true

User · Answer

here is an example what most of have done  using System   class Program       static void Main                 Test  Dot Net Perls            Test  dot net perls               static void Test string input                Console Write  ---             Console Write input           Console WriteLine   ---                          See if the string contains  Net                     bool contains   input Contains  Net                          Write the result                    Console Write  Contains  Net               Console WriteLine contains                         See if the string contains  perls  lowercase                    if  input Contains  perls                          Console WriteLine  Contains  perls                                     See if the string contains  Dot                     if   input Contains  Dot                          Console WriteLine  Doesn t Contain  Dot

User · Answer

Use the function String Contains     an example call   abs Contains  s       to look for lower case s   here is more from MSDN

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You can create your own extention method if you plan to use this a lot   public static class StringExt       public static bool ContainsInvariant this string sourceString  string filter                return sourceString ToLowerInvariant   Contains filter             example usage   public class test       public bool Foo                 const string def    aB           return def ContainsInvariant  s

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You can use the extension method  Contains   from the namespace System Linq   using System Linq                if  abc ToLower   Contains  s          And no  to check if a boolean expression is true  you don t need    true  Since the Contains method is an extension method  my solution appeared to be confusing to some  Here are two versions that don t require you to add using System Linq    if  abc ToLower   IndexOf  s      -1          or   if  abc IndexOf  s   StringComparison CurrentCultureIgnoreCase     -1        Update  If you want to  you can write your own extensions method for easier reuse   public static class MyStringExtensions       public static bool ContainsAnyCaseInvariant this string haystack  char needle                return haystack IndexOf needle  StringComparison InvariantCultureIgnoreCase     -1             public static bool ContainsAnyCase this string haystack  char needle                return haystack IndexOf needle  StringComparison CurrentCultureIgnoreCase     -1            Then you can call them like this   if  def ContainsAnyCaseInvariant  s           or if  def ContainsAnyCase  s          In most cases when dealing with user data  you actually want to use CurrentCultureIgnoreCase  or the ContainsAnyCase extension method   because that way you let the system handle upper lowercase issues  which depend on the language  When dealing with computational issues  like names of HTML tags and so on  you want to use the invariant culture   For example  In Turkish  the uppercase letter I in lowercase is i  without a dot   and not i  with a dot

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You can use the IndexOf method  which has a suitable overload for string comparison types   if  def IndexOf  s   StringComparison OrdinalIgnoreCase   gt   0        Also  you would not need the    true  since an if statement only expects an expression that evaluates to a bool

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It will be hard to work in C  without knowing how to work with strings and booleans  But anyway           String str    ABC           if  str Contains  A                                                    if  str Contains  AB

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The following should work   var abc    sAb   bool exists   abc IndexOf  ab   StringComparison CurrentCultureIgnoreCase   gt  -1

User · Answer

bool containsCharacter   test IndexOf  s   StringComparison OrdinalIgnoreCase   gt   0

[c#] How can I check if a string contains a character in C#?

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