What is the maximum possible length of a NET string

Question

What is the longest string that can be created in  NET  The docs for the String class are silent on this question as far as I can see  so an authoritative answer might require some knowledge of internals  Would the maximum change on a 64-bit system    This is asked more for curiosity than for practical use - I don t intend to create any code that uses gigantic strings

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200 megs    at which point your app grinds to a virtual halt  has about a gig working set memory  and the o s starts to act like you ll need to reboot   static void Main string   args        string s    hello world       for                   s   s   s Substring 0  s Length 10           Console WriteLine s Length            12 13 14 15 16 17 18     158905664 174796230 192275853 211503438

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Since the Length property of System String is an Int32  I would guess that that the maximum length would be 2 147 483 647 chars  max Int32 size   If it allowed longer you couldn t check the Length since that would fail

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The theoretical limit may be 2 147 483 647  but the practical limit is nowhere near that  Since no single object in a  NET program may be over 2GB and the string type uses UTF-16  2 bytes for each character   the best you could do is 1 073 741 823  but you re not likely to ever be able to allocate that on a 32-bit machine   This is one of those situations where  If you have to ask  you re probably doing something wrong

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String allocates dynamic memory size in the heap of your RAM   But string address is stored in stack that occupies 4 bytes of memory

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Based on my highly scientific and accurate experiment  it tops out on my machine well before 1 000 000 000 characters   I m still running the code below to get a better pinpoint    UPDATE  After a few hours  I ve given up  Final results  Can go a lot bigger than 100 000 000 characters  instantly given System OutOfMemoryException at 1 000 000 000 characters   using System  using System Collections Generic   public class MyClass       public static void Main                 int i   100000000          try                       for  i   i  i  lt   int MaxValue  i    5000                                string value   new string  x   i                     WL i                                   catch  Exception exc                        WL i               WL exc                     WL i           RL                region Helper methods      private static void WL object text  params object   args                Console WriteLine text ToString    args                 private static void RL                 Console ReadLine                private static void Break                  System Diagnostics Debugger Break                endregion

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Since String Length is an integer  that is an alias for Int32   its size is limited to Int32 MaxValue unicode characters   -

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The max length of a string on my machine is 1 073 741 791    You see  Strings aren t limited by integer as is commonly believed   Memory restrictions aside  Strings cannot have more than 230  1 073 741 824  characters  since a 2GB limit is imposed by the Microsoft CLR  Common Language Runtime   33 more than my computer allowed   Now  here s something you re welcome to try yourself   Create a new C  console app in Visual Studio and then copy paste the main method here   static void Main string   args        Console WriteLine  String test  by Nicholas John Joseph Taylor         Console WriteLine   nTheoretically  C  should support a string of int MaxValue  but we run out of memory before then          Console WriteLine   nThis is a quickish test to narrow down results to find the max supported length of a string          Console WriteLine   nThe test starts    now  n         int Length   0       string s            int Increment   1000000000     We know that s string with the length of 1000000000 causes an out of memory exception       LoopPoint          Make a string appendage the length of the value of Increment      StringBuilder StringAppendage   new StringBuilder         for  int CharacterPosition   0  CharacterPosition  lt  Increment  CharacterPosition                  StringAppendage Append  0                   Repeatedly append string appendage until an out of memory exception is thrown       try               if  Increment  gt  0              while  Length  lt  int MaxValue                                Length    Increment                   s    StringAppendage ToString       Append string appendage the length of the value of Increment                  Console WriteLine  s Length       s Length     at     DateTime Now ToString  dd MM yyyy HH mm                               catch  OutOfMemoryException ex     Note  Any other exception will crash the program                Console WriteLine   n    ex Message     at     DateTime Now ToString  dd MM yyyy HH mm                    Length -  Increment           Increment    10           Console WriteLine  After decimation  the value of Increment is     Increment                    catch  Exception ex2                Console WriteLine   n    ex2 Message     at     DateTime Now ToString  dd MM yyyy HH mm                    Console WriteLine  Press a key to continue                Console ReadKey                if  Increment  gt  0                goto LoopPoint              Console WriteLine  Test complete          Console WriteLine   nThe max length of a string is     s Length              Console WriteLine   nPress any key to continue          Console ReadKey         My results were as follows      String test  by Nicholas John Joseph Taylor      Theoretically  C  should support a string of int MaxValue  but we run   out of memory before then       This is a quickish test to narrow down results to find the max   supported length of a string       The test starts    now       s Length   1000000000 at 08 05 2019 12 06      Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 06  After decimation  the value of Increment is   100000000       Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 06  After decimation  the value of Increment is   10000000  s Length   1010000000 at 08 05 2019 12 06 s Length   1020000000 at 08 05 2019 12 06 s Length   1030000000 at 08 05 2019   12 06 s Length   1040000000 at 08 05 2019 12 06 s Length   1050000000   at 08 05 2019 12 06 s Length   1060000000 at 08 05 2019 12 06 s Length     1070000000 at 08 05 2019 12 06      Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 06  After decimation  the value of Increment is 1000000    s Length   1071000000 at 08 05 2019 12 06 s Length   1072000000 at   08 05 2019 12 06 s Length   1073000000 at 08 05 2019 12 06      Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 06  After decimation  the value of Increment is 100000    s Length   1073100000 at 08 05 2019 12 06 s Length   1073200000 at   08 05 2019 12 06 s Length   1073300000 at 08 05 2019 12 06 s Length     1073400000 at 08 05 2019 12 06 s Length   1073500000 at 08 05 2019   12 06 s Length   1073600000 at 08 05 2019 12 06 s Length   1073700000   at 08 05 2019 12 06      Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 06  After decimation  the value of Increment is 10000    s Length   1073710000 at 08 05 2019 12 06 s Length   1073720000 at   08 05 2019 12 06 s Length   1073730000 at 08 05 2019 12 06 s Length     1073740000 at 08 05 2019 12 06      Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 06  After decimation  the value of Increment is 1000    s Length   1073741000 at 08 05 2019 12 06      Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 06  After decimation  the value of Increment is 100    s Length   1073741100 at 08 05 2019 12 06 s Length   1073741200 at   08 05 2019 12 06 s Length   1073741300 at 08 05 2019 12 07 s Length     1073741400 at 08 05 2019 12 07 s Length   1073741500 at 08 05 2019   12 07 s Length   1073741600 at 08 05 2019 12 07 s Length   1073741700   at 08 05 2019 12 07      Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 07  After decimation  the value of Increment is 10    s Length   1073741710 at 08 05 2019 12 07 s Length   1073741720 at   08 05 2019 12 07 s Length   1073741730 at 08 05 2019 12 07 s Length     1073741740 at 08 05 2019 12 07 s Length   1073741750 at 08 05 2019   12 07 s Length   1073741760 at 08 05 2019 12 07 s Length   1073741770   at 08 05 2019 12 07 s Length   1073741780 at 08 05 2019 12 07 s Length     1073741790 at 08 05 2019 12 07      Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 07  After decimation  the value of Increment is 1    s Length   1073741791 at 08 05 2019 12 07      Exception of type  System OutOfMemoryException  was thrown  at   08 05 2019 12 07  After decimation  the value of Increment is 0  Test   complete       The max length of a string is 1073741791       Press any key to continue    The max length of a string on my machine is 1073741791    I d appreciate it very much if people could post their results as a comment below    It will be interesting to learn if people get the same or different results

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For anyone coming to this topic late  I could see that hitscan s  you probably shouldn t do that  might cause someone to ask what they should do     The StringBuilder class is often an easy replacement  Consider one of the stream-based classes especially  if your data is coming from a file   The problem with s     stuff  is that it has to allocate a completely new area to hold the data and then copy all of the old data to it plus the new stuff - EACH AND EVERY LOOP ITERATION  So  adding five bytes to 1 000 000 with s     stuff  is extremely costly  If what you want is to just write five bytes to the end and proceed with your program  you have to pick a class that leaves some room for growth   StringBuilder sb   new StringBuilder 5000   for                      sb Append  stuff            StringBuilder will auto-grow by doubling when it s limit is hit  So  you will see the growth pain once at start  once at 5 000 bytes  again at 10 000  again at 20 000  Appending strings will incur the pain every loop iteration

[.net] What is the maximum possible length of a .NET string?

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