How do I truncate a NET string

Question

I would like to truncate a string such that its length is not longer than a given value   I am writing to a database table and want to ensure that the values I write meet the constraint of the column s datatype   For instance  it would be nice if I could write the following   string NormalizeLength string value  int maxLength        return value Substring 0  maxLength       Unfortunately  this raises an exception because maxLength generally exceeds the boundaries of the string value   Of course  I could write a function like the following  but I was hoping that something like this already exists   string NormalizeLength string value  int maxLength        return value Length  lt   maxLength   value   value Substring 0  maxLength        Where is the elusive API that performs this task   Is there one

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I did mine in one line sort of like this  value   value Length  gt  1000   value Substring 0  1000    value

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There isn t a Truncate   method on string  unfortunately  You have to write this kind of logic yourself  What you can do  however  is wrap this in an extension method so you don t have to duplicate it everywhere   public static class StringExt       public static string Truncate this string value  int maxLength                if  string IsNullOrEmpty value   return value          return value Length  lt   maxLength   value   value Substring 0  maxLength              Now we can write   var someString          someString   someString Truncate 2

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Just in case there s not enough answers here  here s mine     public static string Truncate this string str                                 int totalLength                                 string truncationIndicator             if  string IsNullOrEmpty str     str Length  lt  totalLength           return str       return str Substring 0  totalLength - truncationIndicator Length                truncationIndicator      to use    I use it like this  Truncate 5

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In C  8 the new Ranges feature can be used     value   value   Math Min 30  value Length

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Or instead of the ternary operator  you could use Math min  public static class StringExt       public static string Truncate  this string value  int maxLength                 if  string IsNullOrEmpty value     return value             return value Substring 0  Math Min value Length  maxLength

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For the sake of  over complexity I ll add my overloaded version which replaces the last 3 characters with an ellipsis in respect with the maxLength parameter   public static string Truncate this string value  int maxLength  bool replaceTruncatedCharWithEllipsis   false        if  replaceTruncatedCharWithEllipsis  amp  amp  maxLength  lt   3          throw new ArgumentOutOfRangeException  maxLength                maxLength should be greater than three when replacing with an ellipsis          if  String IsNullOrWhiteSpace value            return String Empty       if  replaceTruncatedCharWithEllipsis  amp  amp          value Length  gt  maxLength                return value Substring 0  maxLength - 3                      return value Substring 0  Math Min value Length  maxLength

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I d Recommend using the substring method for the same effective functionality           Gets first n characters      string subString   inputString Substring 0  n     This has the benefit of letting you splice your string from either side or even somewhere in the middle without writing additional methods  Hope that helps      For additional reference  https   www dotnetperls com substring

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I prefer jpierson s answer  but none of the examples here that I can see are handling an invalid maxLength parameter  such as when maxLength  lt  0   Choices would be either handle the error in a try catch  clamp the maxLength parameter min to 0  or if maxLength is less than 0 return an empty string   Not optimized code   public string Truncate this string value  int maximumLength        if  string IsNullOrEmpty value     true    return value        if  maximumLen  lt  0    return String Empty        if  value Length  gt  maximumLength    return value Substring 0  maximumLength         return value

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You can create a Truncate extension method that compares the max length relative to the string length and calls Substring if needed  If you want null handling behavior that parallels that of Substring  don t include a null check  That way  just as str Substring 0  10  throws a NullReferenceException if str is null  so will str Truncate 10   public static class StringExtensions       public static string Truncate this string value  int maxLength    gt          value Length  lt   maxLength   value   value Substring 0  maxLength

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public static string Truncate  this string value  int maxLength                 if  string IsNullOrEmpty value     return value             return new string value Take maxLength  ToArray       use LINQ and be happy

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A similar variant with C  6 s Null propagation operator  public static string Truncate this string value  int maxLength        return value  Length  lt   maxLength   value   value  Substring 0  maxLength       Please note  we are essentially checking if value is null twice here

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The  NET Framework has an API to truncate a string like this   Microsoft VisualBasic Strings Left string  int     But in a C  app you ll probably prefer to roll your own than taking a dependency on Microsoft VisualBasic dll  whose main raison d etre is backwards compatibility

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Still no Truncate method in 2016 for C  strings   But - Using C  6 0 Syntax   public static class StringExtension     public static string Truncate this string s  int max            return s  Length  gt  max   s Substring 0  max    s    throw new ArgumentNullException s            It works like a charm    Truncate me  Truncate 8   Result   Truncate

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Based on this  and this  here are two versions that will work for negative values of  up to  values as well  This first one doesn t allow negative values silently by capping at 0  public static string Truncate this string value  int maxLength        return string IsNullOrEmpty value            value           value Substring 0  Math Max 0  Math Min value Length  maxLength        This one goes in circle  private static int Mod this int a  int n    gt     a    n   lt  0    n   0    a   public static string Truncate this string value  int maxLength        return string IsNullOrEmpty value            value           value Substring 0  maxLength Mod value Length

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Taking  CaffGeek and simplifying it   public static string Truncate this string value  int maxLength                return string IsNullOrEmpty value    value   value Substring 0  Math Min value Length  maxLength

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As an addition to the possibilities discussed above I d like to share my solution  It s an extension method that allows null  returns string Empty  also there is a second  Truncate   for using it with an ellipsis  Beware  it s not performance optimized   public static string Truncate this string value  int maxLength    gt       value    string Empty  Substring 0   value  Length    0   lt    maxLength  lt  0   0   maxLength     value  Length    0     maxLength  lt  0   0   maxLength    public static string Truncate this string value  int maxLength  string ellipsis    gt      string Concat value Truncate maxLength -    value  Length    0   gt  maxLength   ellipsis   null   Length    0      value  Length    0   gt  maxLength   ellipsis   null   Truncate maxLength

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Truncate String  public static string TruncateText string strText  int intLength        if    string IsNullOrEmpty strText                                                     split the text          var words   strText Split                   calculate the number of words            based on the provided characters length             use an average of 7 6 chars per word          int wordLength   Convert ToInt32 Math Ceiling intLength   7 6                if the text is shorter than the length             display the text without changing it          if  words Length  lt   wordLength              return strText Trim                                put together a shorter text            based on the number of words         return string Join      words Take wordLength            Trim                  else                       return

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Kndly note that truncating a string not merely means justing cutting a string at a specified length alone but have to take care not to split the word    eg string   this is a test string    I want to cut it at 11   If we use any of the method given above the result will be  this is a te  This is not the thing we want  The method i am using may also not so perfect but it can handle most of the situation  public string CutString string source  int length            if  source   null    source Length  lt  length                        return source                    int nextSpace   source LastIndexOf      length           return string Format   0       input Substring 0   nextSpace  gt  0    nextSpace   length  Trim

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My two cents with example length of 30       var truncatedInput   string IsNullOrEmpty input           string Empty          input Substring 0  Math Min input Length  30

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In  NET 4 0 you can use the Take method   string Concat myString Take maxLength      Not tested for efficiency

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I know this is an old question  but here is a nice solution   public static string Truncate this string text  int maxLength  string suffix                string str   text      if  maxLength  gt  0                int length   maxLength - suffix Length          if  length  lt   0                        return str                    if   text    null   amp  amp   text Length  gt  maxLength                         return  text Substring 0  length  TrimEnd new char 0     suffix                       return str     var myString    hello world  var myTruncatedString   myString Truncate 4     Returns  hello

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Here is a vb net solution  mark that the if  although ugly  statement improves performance because we do not need the substring statement when string is already smaller than maxlength    By making it an extention to string it is easy to use       lt System Runtime CompilerServices Extension   gt        Public Function Truncate String  1 As String  maxlength As Integer  As String         If Not String IsNullOrEmpty String  1  AndAlso String  1 Length  gt  maxlength Then             Return String  1 Substring 0  maxlength          Else             Return String  1         End If     End Function

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Seems no one has posted this yet   public static class StringExt       public static string Truncate this string s  int maxLength                return s    null  amp  amp  s Length  gt  maxLength   s Substring 0  maxLength    s            Using the  amp  amp  operator makes it marginally better than the accepted answer

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Because performance testing is fun   using linqpad extension methods   var val   string Concat Enumerable Range 0  50  Select i   gt  i   10     foreach var limit in new     10  25  44  64        new Perf lt string gt               newstring    limit  n   gt  new string val Take limit  ToArray                  concat    limit  n   gt  string Concat val Take limit                 truncate    limit  n   gt  val Substring 0  Math Min val Length  limit                 smart-trunc    limit  n   gt  val Length  lt   limit   val   val Substring 0  limit                stringbuilder    limit  n   gt  new StringBuilder val  0  Math Min val Length  limit   limit  ToString            Vs      The truncate method was  significantly  faster   microoptimization  Early        truncate10 5788 ticks elapsed  0 5788 ms   in 10K reps  5 788E-05 ms per     smart-trunc10 8206 ticks elapsed  0 8206 ms   in 10K reps  8 206E-05 ms per     stringbuilder10 10557 ticks elapsed  1 0557 ms   in 10K reps  0 00010557 ms per     concat10 45495 ticks elapsed  4 5495 ms   in 10K reps  0 00045495 ms per     newstring10 72535 ticks elapsed  7 2535 ms   in 10K reps  0 00072535 ms per        Late        truncate44 8835 ticks elapsed  0 8835 ms   in 10K reps  8 835E-05 ms per     stringbuilder44 13106 ticks elapsed  1 3106 ms   in 10K reps  0 00013106 ms per     smart-trunc44 14821 ticks elapsed  1 4821 ms   in 10K reps  0 00014821 ms per     newstring44 144324 ticks elapsed  14 4324 ms   in 10K reps  0 00144324 ms per     concat44 174610 ticks elapsed  17 461 ms   in 10K reps  0 0017461 ms per        Too Long        smart-trunc64 6944 ticks elapsed  0 6944 ms   in 10K reps  6 944E-05 ms per     truncate64 7686 ticks elapsed  0 7686 ms   in 10K reps  7 686E-05 ms per     stringbuilder64 13314 ticks elapsed  1 3314 ms   in 10K reps  0 00013314 ms per     newstring64 177481 ticks elapsed  17 7481 ms   in 10K reps  0 00177481 ms per     concat64 241601 ticks elapsed  24 1601 ms   in 10K reps  0 00241601 ms per

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I figured I would throw in my implementation since I believe it covers all of the cases that have been touched on by the others and does so in a concise way that is still readable   public static string Truncate this string value  int maxLength        if   string IsNullOrEmpty value   amp  amp  value Length  gt  maxLength                return value Substring 0  maxLength              return value      This solution mainly builds upon the Ray s solution and opens up the method for use as an extension method by using the this keyword just as LBushkin does in his solution

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TruncateString  public static string  TruncateString string input  int charaterlimit        int characterLimit   charaterlimit      string output   input          Check if the string is longer than the allowed amount        otherwise do nothing     if  output Length  gt  characterLimit  amp  amp  characterLimit  gt  0                   cut the string down to the maximum number of characters         output   output Substring 0  characterLimit              Check if the character right after the truncate point was a space            if not  we are in the middle of a word and need to remove the rest of it         if  input Substring output Length  1                                int LastSpace   output LastIndexOf                       if we found a space then  cut back to that space             if  LastSpace    -1                                output   output Substring 0  LastSpace                                      Finally  add the               output                     return output

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I know there are a ton of answers already but my need was to keep the beginning and end of the string intact but shorten it to under the max length       public static string TruncateMiddle string source                if  String IsNullOrWhiteSpace source     source Length  lt  260               return source           return string Format   0     1                 source Substring 0  235               source Substring source Length - 20            This is for creating SharePoint URLs that have a max length of 260 characters    I didn t make length a parameter since it is a constant 260   I also didn t make the first substring length a parameter because I want it to break at a specific point   Finally  the second substring is the length of the source - 20 since I know the folder structure     This could easily be adapted to your specific needs

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Another solution   return input Substring 0  Math Min input Length  maxLength

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I know there are a ton of answers here already  but this is the one I have gone with  which handles both null strings and the situation where the length passed in is negative   public static string Truncate this string s  int length        return string IsNullOrEmpty s     s Length  lt   length   s            length  lt   0   string Empty            s Substring 0  length

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Why not   string NormalizeLength string value  int maxLength          check String IsNullOrEmpty value  and act on it       return value PadRight maxLength  Substring 0  maxLength       i e  in the event value Length  lt  maxLength pad spaces to the end or truncate the excess

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The simplest method in recent C  would be  string Trunc string s  int len    gt  s  Length  gt  len   s Substring 0  len    s   It returns truncated value for longer strings and original string for other cases - including null input - which is treated by   unary operator

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This is the code I usually use   string getSubString string value  int index  int length                        if  string IsNullOrEmpty value     value Length  lt   length                                return value                            System Text StringBuilder sb   new System Text StringBuilder                for  int i   index  i  lt  length  i                                  sb AppendLine value i  ToString                               return sb ToString

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There is nothing in  net for this that I am aware of - here is my version which adds         public static string truncateString string originalString  int length      if  string IsNullOrEmpty originalString        return originalString        if  originalString Length  gt  length       return originalString Substring 0  length                 else      return originalString

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The popular library Humanizer has a Truncate method  To install with NuGet  Install-Package Humanizer

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You could use LINQ    it eliminates the need to check string length   Admittedly maybe not the most efficient  but it s fun   string result   string Join     value Take maxLength        NET 4 Join   or  string result   new string value Take maxLength  ToArray

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