Extract only right most n letters from a string

Question

How can I extract a substring which is composed of the rightmost six letters from another string   Ex  my string is  PER 343573   Now I want to extract only  343573    How can I do this

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Write an extension method to express the Right n   function  The function should deal with null or empty strings returning an empty string  strings shorter than the max length returning the original string and strings longer than the max length returning the max length of rightmost characters   public static string Right this string sValue  int iMaxLength        Check if the value is valid   if  string IsNullOrEmpty sValue             Set valid empty string as string could be null     sValue   string Empty        else if  sValue Length  gt  iMaxLength            Make the string no longer than the max length     sValue   sValue Substring sValue Length - iMaxLength  iMaxLength            Return the string   return sValue

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Here s the solution I use    It checks that the input string s length isn t lower than the asked length  The solutions I see posted above don t take this into account unfortunately - which can lead to crashes            lt summary gt          Gets the last x- lt paramref name  amount   gt  of characters from the given string          If the given string s length is smaller than the requested  lt see cref  amount   gt  the full string is returned          If the given  lt paramref name  amount   gt  is negative  an empty string will be returned           lt  summary gt           lt param name  string  gt The string from which to extract the last x- lt paramref name  amount   gt  of characters  lt  param gt           lt param name  amount  gt The amount of characters to return  lt  param gt           lt returns gt The last x- lt paramref name  amount   gt  of characters from the given string  lt  returns gt      public static string GetLast this string  string  int amount                if   string    null                return  string                     if  amount  lt  0                return String Empty                     if  amount  gt    string Length                return  string            else               return  string Substring  string Length - amount

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Probably nicer to use an extension method   public static class StringExtensions       public static string Right this string str  int length                return str Substring str Length - length  length             Usage  string myStr    PER 343573   string subStr   myStr Right 6

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var str    PER 343573   var right6   string IsNullOrWhiteSpace str    string Empty                 str Length  lt  6   str                 str Substring str Length - 6       343573     alternative var alt right6   new string str Reverse   Take 6  Reverse   ToArray         343573    this supports any number of character in the str  the alternative code not support null string  and  the first is faster and the second is more compact   i prefer the second one if knowing the str containing short string  if it s long string the first one is more suitable   e g   var str       var right6   string IsNullOrWhiteSpace str    string Empty                 str Length  lt  6   str                 str Substring str Length - 6            alternative var alt right6   new string str Reverse   Take 6  Reverse   ToArray             or  var str    123   var right6   string IsNullOrWhiteSpace str    string Empty                 str Length  lt  6   str                 str Substring str Length - 6       123     alternative var alt right6   new string str Reverse   Take 6  Reverse   ToArray         123

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Since you are using  NET  which all compiles to MSIL  just reference Microsoft VisualBasic  and use Microsoft s built-in Strings Right method  using Microsoft VisualBasic      string input    quot PER 343573 quot   string output   Strings Right input  6    No need to create a custom extension method or other work  The result is achieved with one reference and one simple line of code  As further info on this  using Visual Basic methods with C  has been documented elsewhere  I personally stumbled on it first when trying to parse a file  and found this SO thread on using the Microsoft VisualBasic FileIO TextFieldParser class to be extremely useful for parsing  csv files

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Guessing at your requirements but the following regular expression will yield only on 6 alphanumerics before the end of the string and no match otherwise   string result   Regex Match  PER 343573      a-zA-Z d  6     Value

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Another solution that may not be mentioned  S Substring S Length  lt  6   0   S Length - 6

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MSDN  String mystr    PER 343573   String number   mystr Substring mystr Length-6     EDIT  too slow

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Null Safe Methods    Strings shorter than the max length returning the original string  String Right Extension Method  public static string Right this string input  int count    gt      String Join      input       ToCharArray   Reverse   Take count  Reverse       String Left Extension Method  public static string Left this string input  int count    gt      String Join      input       ToCharArray   Take count

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This is the method I use  I like to keep things simple   private string TakeLast string input  int num        if  num  gt  input Length                num   input Length            return input Substring input Length - num

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if you are not sure of the length of your string  but you are sure of the words count  always 2 words in this case  like  xxx yyyyyy   you d better use split     string Result    PER 343573  Split      1     this always returns the second word of your string

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using Microsoft visualBasic    public class test    public void main       string randomString    Random Word      print  Strings right randomString 4             output is  Word

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Use this   String text    PER 343573   String numbers   text  if  text Length  gt  6        numbers   text Substring text Length - 6

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I use the Min to prevent the negative situations and also handle null strings      lt summary gt          Returns a string containing a specified number of characters from the right side of a string           lt  summary gt      public static string Right this string value  int length                string result   value          if  value    null              result   value Substring 0  Math Min value Length  length            return result

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using System   public static class DataTypeExtensions        region Methods      public static string Left this string str  int length                str    str    string Empty           return str Substring 0  Math Min length  str Length               public static string Right this string str  int length                str    str    string Empty           return  str Length  gt   length                str Substring str Length - length  length                str              endregion     Shouldn t error  returns nulls as empty string  returns trimmed or base values   Use it like  testx  Left 4  or str Right 12

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This isn t exactly what you are asking for  but just looking at the example  it appears that you are looking for the numeric section of the string   If this is always the case  then a good way to do it would be using a regular expression   var regex  new Regex   n     string numberString   regex Match page  Value

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Without resorting to the bit converter and bit shifting  need to be sure of encoding  this is fastest method I use as an extension method  Right    string myString    123456789123456789    if  myString  gt  6             char   cString   myString ToCharArray            Array Reverse myString           Array Resize ref myString  6           Array Reverse myString           string val   new string myString

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Use this   string mystr    PER 343573   int number   Convert ToInt32 mystr Replace  PER

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string SubString   MyString Substring MyString Length-6

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Just a thought   public static string Right this string  this  int length        return  this Substring Math Max  this Length - length  0

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s - your string   n - maximum number of right characters to take at the end of string  new Regex         1 n       Replace s   1

[c#] Extract only right most n letters from a string

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