Check if a value is in an array C

Question

How do I check if a value is in an array in C    Like  I want to create an array with a list of printer names   These will be fed to a method  which will look at each string in turn  and if the string is the same as a value in an array  do that action   For example   string   printer     jupiter    neptune    pangea    mercury    sonic    foreach  p in printer       PrinterSetup p            These are the names of the printers  they are being fed to the PrinterSetup method   PrinterSetup will look sort of like this  some pseudocode    public void PrinterSetup printer       if  printer     jupiter               Process Start  BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC             How do I format if  printer     jupiter   in a way that C  can recognize

User · Answer

string   array      cat    dot    perls         Use Array Exists in different ways  bool a   Array Exists array  element   gt  element     perls    bool b   Array Exists array  element   gt  element     python    bool c   Array Exists array  element   gt  element StartsWith  d     bool d   Array Exists array  element   gt  element StartsWith  x         Display bools  Console WriteLine a   Console WriteLine b   Console WriteLine c   Console WriteLine d   ----------------------------output-----------------------------------   1 True 2 False 3 True 4 False

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public static bool Contains Array a  object val                return Array IndexOf a  val     -1

User · Answer

Note  The question is about arrays of strings  The mentioned routines are not to be mixed with the  Contains method of single strings  I would like to add an extending answer referring to different C  versions and because of two reasons   The accepted answer requires Linq which is perfectly idiomatic C  while it does not come without costs  and is not available in C  2 0 or below  When an array is involved  performance may matter  so there are situations where you want to stay with Array methods   No answer directly attends to the question where it was asked also to put this in a function  As some answers are also mixing strings with arrays of strings  this is not completely unimportant     Array Exists   is a C   NET 2 0 method and needs no Linq  Searching in arrays is O n   For even faster access use HashSet or similar collections  Since  NET 3 5 there also exists a generic method Array lt T gt  Exists     public void PrinterSetup string   printer       if  Array Exists printer  x   gt  x     quot jupiter quot               Process Start  quot BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC quot            You could write an own extension method  C  3 0 and above  to add the syntactic sugar to get the same similar  quot  Contains quot  as for strings for all arrays without including Linq     Using the generic extension method below as requested  public void PrinterSetup string   printer       if  printer ArrayContains  quot jupiter quot               Process Start  quot BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC quot            public static bool ArrayContains lt T gt  this T   thisArray  T searchElement          If you want this to find  quot null quot  values  you could change the code here    return Array Exists lt T gt  thisArray  x   gt  x Equals searchElement       In this case this ArrayContains   method is used and not the Contains method of Linq  The elsewhere mentioned  Contains methods refer to List lt T gt  Contains  since C  2 0  or ArrayList Contains  since C  1 1   but not to arrays itself directly

User · Answer

Consider using HashSet lt T gt  Class for the sake of lookup performance      This method is an O 1  operation           HashSet lt T gt  Contains Method  T   MSDN    For example   class PrinterInstaller       private static readonly HashSet lt string gt  PrinterNames   new HashSet lt string gt                         jupiter    neptune    pangea    mercury    sonic                  public void Setup string printerName                if   PrinterNames Contains printerName                         throw new ArgumentException  Unknown printer name    printerName

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You are just missing something in your method   public void PrinterSetup string printer       if  printer     jupiter               Process Start  BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC              Just add string and you ll be fine

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Something like this   string   printer     jupiter    neptune    pangea    mercury    sonic    PrinterSetup printer       redefine PrinterSetup this way  public void PrinterSetup string   printer        foreach  p in printer Where c   gt  c     jupiter                  Process Start  BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC

User · Answer

Add necessary namespace  using System Linq    Then you can use linq Contains   method  string   printer     jupiter    neptune    pangea    mercury    sonic    if printer Contains  jupiter          Process Start  BLAH BLAH CODE TO ADD PRINTER VIA WINDOWS EXEC

User · Answer

Add using System Linq  at the top of your file  Then you can do  if   new      quot foo quot    quot bar quot    quot baaz quot    Contains  quot bar quot

User · Answer

Not very clear what your issue is  but it sounds like you want something like this       List lt string gt  printer   new List lt string gt   new       jupiter    neptune    pangea    mercury    sonic            if  printer Exists  p   gt  p Equals   jupiter

User · Answer

I searched now over 2h to find a nicely way how to find duplicates in a list and how to remove them  Here is the simplest answer     Copy the string array with the filtered data of the analytics db into an list    a list should be easier to use List lt string gt  list filtered data   new List lt string gt  analytics db filtered data       Get distinct elements and convert into a list again  List lt string gt  distinct   list filtered data Distinct   ToList      The Output will look like this  Duplicated Elements will be removed in the new list called distinct

[c#] Check if a value is in an array (C#)

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