Make first letter of a string upper case with maximum performance

Question

I have a DetailsView with a TextBox and I want the input data be saved always with the FIRST LETTER IN CAPITAL   Example    red  -- gt   Red   red house  -- gt    Red house    How can I achieve this maximizing performance     NOTE  Based on the answers and the comments under the answers  many people think this is asking about capitalizing all words in the string  E g    gt  Red House It isn t  but if that is what you seek  look for one of the answers that uses TextInfo s ToTitleCase method   NOTE  Those answers are incorrect for the question actually asked   See TextInfo ToTitleCase doc for caveats  doesn t touch all-caps words - they are considered acronyms  may lowercase letters in middle of words that  shouldn t  be lowered  e g   McDonald      Mcdonald   not guaranteed to handle all culture-specific subtleties re capitalization rules      NOTE  The question is ambiguous as to whether letters after the first should be forced to lower case   The accepted answer assumes that only the first letter should be altered  If you want to force all letters in the string except the first to be lower case  look for an answer containing ToLower  and not containing ToTitleCase

User · Answer

The right way is to use Culture   System Globalization CultureInfo CurrentCulture TextInfo ToTitleCase word ToLower      Note  This will capitalise each word within a string  e g   red house  --   Red House   The solution will also lower-case capitalisation within words  e g   old McDonald  --   Old Mcdonald

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the following function is correct for all ways   static string UppercaseWords string value        char   array   value ToCharArray           Handle the first letter in the string      if  array Length  gt   1                if  char IsLower array 0                          array 0    char ToUpper array 0                           Scan through the letters  checking for spaces             Uppercase the lowercase letters following spaces      for  int i   1  i  lt  array Length  i                  if  array i - 1                                if  char IsLower array i                                  array i    char ToUpper array i                                      return new string array       I found that here

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string s Val    test   if  s Val             s Val    char ToUpper s Val 0       if  s Val Length  gt  1             s Val    s Val Substring 1

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Updated to C  8  public static class StringExtensions       public static string FirstCharToUpper this string input    gt          input switch                       null   gt  throw new ArgumentNullException nameof input                     gt  throw new ArgumentException    nameof input   cannot be empty   nameof input                    gt  input First   ToString   ToUpper     input Substring 1                 C  7  public static class StringExtensions       public static string FirstCharToUpper this string input                switch  input                        case null  throw new ArgumentNullException nameof input                case     throw new ArgumentException    nameof input   cannot be empty   nameof input                default  return input First   ToString   ToUpper     input Substring 1                       Really old answers  public static string FirstCharToUpper string input        if  String IsNullOrEmpty input           throw new ArgumentException  ARGH         return input First   ToString   ToUpper     String Join     input Skip 1        EDIT  This version is shorter  For a faster solution take a look at Equiso s answer  public static string FirstCharToUpper string input        if  String IsNullOrEmpty input           throw new ArgumentException  ARGH         return input First   ToString   ToUpper     input Substring 1       EDIT 2  Probably the fastest solution is Darren s  There s even a benchmark  although I would change it s string IsNullOrEmpty s  validation to throw an exception since the original requirement expects for a first letter to exist so it can be uppercased  Note that this code works for a generic string and not particularly on valid values from the Textbox

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Check if the string is not null then convert the first character to upper case and the rest of them to lower case    public static string FirstCharToUpper string str        return str  First   ToString   ToUpper     str  Substring 1  ToLower

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Fastest method     private string Capitalize string s           if  string IsNullOrEmpty s                         return string Empty                    char   a   s ToCharArray            a 0    char ToUpper a 0            return new string a       Tests show next results  string with 10000000 symbols as input   Test results

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private string capitalizeFirstCharacter string format          if  string IsNullOrEmpty format            return string Empty       else          return char ToUpper format 0     format ToLower   Substring 1

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Recently I had a similar requirement and remembered that the LINQ function Select   provides an index   string input  string output   input    red house   output   String Concat input Select  currentChar  index    gt  index    0   Char ToUpper currentChar    currentChar      output    Red house    Since I need that very often I made an extension method for the string type   public static class StringExtensions       public static string FirstLetterToUpper this string input                if  string IsNullOrEmpty input               return string Empty          return String Concat input Select  currentChar  index    gt  index    0   Char ToUpper currentChar    currentChar              Please note that only the first letter is converted to upper case - all remaining characters are not touched  If you need the other characters to be lower case you may also call Char ToLower currentChar  for index   0 or call ToLower   on the whole string in the first place   Regarding performance I compared the code with the solution from Darren  On my machine Darren s code is about 2 times faster which is no surprise since he s directly editing only the first letter within a char array  So I suggest you take Darren s code if you need the fastest solution available  If you want to integrate other string manipulations as well it may be convenient to have the expressive power of a lambda function touching the characters of the input string - you can easily extend this function - so I leave this solution here

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Seems like none of the solutions given here will deal with a white space before the string   Just adding this as a thought   public static string SetFirstCharUpper2 string aValue  bool aIgonreLeadingSpaces   true        if  string IsNullOrWhiteSpace aValue           return aValue       string trimmed   aIgonreLeadingSpaces               aValue TrimStart                 aValue       return char ToUpper trimmed 0     trimmed Substring 1          It should handle this won t work on other answers  that sentence has a space in the beginning   and if you don t like the space trimming  just pass a false as second parameter  or change the default to false  and pass true if you want to deal with space

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public static string ToInvarianTitleCase this string self        if  string IsNullOrWhiteSpace self                 return self             return CultureInfo InvariantCulture TextInfo ToTitleCase self

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Using string Create   and avoiding the throw keyword in our method  yes  you read it right   we can take Marcell s answer one step further  Also  my method handles strings of arbitrary length  e g  several megabytes of text   public static string L33t this string s        static void ThrowError     gt  throw new ArgumentException  quot There is no first letter quot         if  string IsNullOrEmpty s           ThrowError                            No  quot throw quot  keyword to avoid costly IL      return string Create s Length  s   chars  state    gt                state AsSpan   CopyTo chars           No slicing to save some CPU cycles         chars 0    char ToUpper chars 0               Performance Here are the numbers for benchmarks run on  NET Core 3 1 7  x64  I added a longer string to pinpoint the cost of extra copies     Method                   Data        Mean       Error      StdDev      Median    --------  ---------------------  ----------  ----------  ----------  ----------        L33t                    red    8 545 ns   0 4612 ns   1 3308 ns    8 075 ns     Marcell                    red    9 153 ns   0 3377 ns   0 9471 ns    8 946 ns        L33t              red house    7 715 ns   0 1741 ns   0 4618 ns    7 793 ns     Marcell              red house   10 537 ns   0 5002 ns   1 4351 ns   10 377 ns        L33t   red r     house  89    11 121 ns   0 6774 ns   1 9106 ns   10 612 ns     Marcell   red r     house  89    16 739 ns   0 4468 ns   1 3033 ns   16 853 ns    Full test code using System  using BenchmarkDotNet Attributes  using BenchmarkDotNet Running   namespace CorePerformanceTest       class Program               static void Main string   args                        var summary   BenchmarkRunner Run lt StringUpperTest gt                          public class StringUpperTest                Params  quot red quot    quot red house quot    quot red red red red red red red red red red red red red red red red red red red red red house quot            public string Data                    Benchmark          public string Marcell     gt  Data Marcell              Benchmark          public string L33t     gt  Data L33t               internal static class StringExtensions               public static string Marcell this string s                        if  string IsNullOrEmpty s                   throw new ArgumentException  quot There is no first letter quot                 Span lt char gt  a   stackalloc char s Length               s AsSpan 1  CopyTo a Slice 1                a 0    char ToUpper s 0                return new string a                              public static string L33t this string s                        static void ThrowError     gt  throw new ArgumentException  quot There is no first letter quot                 if  string IsNullOrEmpty s                   ThrowError       IMPORTANT  Do not  quot throw quot  here               return string Create s Length  s   chars  state    gt                                state AsSpan   CopyTo chars                   chars 0    char ToUpper chars 0                                       Please let me know if you can make it any faster

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Simplest and fastest way is to replace the first char of the string by making it an upper case char   string str    test   lt br gt  str   str Replace str 0   char ToUpper str 0

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As this question is about maximizing performance I adopted Darren s version to use Spans  which reduces garbage and improves speed by about 10                 lt summary gt              Returns the input string with the first character converted to uppercase              lt  summary gt          public static string ToUpperFirst this string s                        if  string IsNullOrEmpty s                   throw new ArgumentException  There is no first letter                 Span lt char gt  a   stackalloc char s Length               s AsSpan 1  CopyTo a Slice 1                a 0    char ToUpper s 0                return new string a               Performance     Method        Data        Mean       Error      StdDev    --------  ----------  ----------  ----------  ----------      Carlos         red   107 29 ns   2 2401 ns   3 9234 ns      Darren         red    30 93 ns   0 9228 ns   0 8632 ns     Marcell         red    26 99 ns   0 3902 ns   0 3459 ns      Carlos   red house   106 78 ns   1 9713 ns   1 8439 ns      Darren   red house    32 49 ns   0 4253 ns   0 3978 ns     Marcell   red house    27 37 ns   0 3888 ns   0 3637 ns     Full test code  using System  using System Linq   using BenchmarkDotNet Attributes   namespace CorePerformanceTest       public class StringUpperTest                Params  red    red house            public string Data            Benchmark          public string Carlos     gt  Data Carlos              Benchmark          public string Darren     gt  Data Darren              Benchmark          public string Marcell     gt  Data Marcell               internal static class StringExtensions               public static string Carlos this string input    gt              input switch                               null   gt  throw new ArgumentNullException nameof input                         gt  throw new ArgumentException    nameof input   cannot be empty   nameof input                        gt  input First   ToString   ToUpper     input Substring 1                          public static string Darren this string s                        if  string IsNullOrEmpty s                   throw new ArgumentException  There is no first letter                 char   a   s ToCharArray                a 0    char ToUpper a 0                return new string a                      public static string Marcell this string s                        if  string IsNullOrEmpty s                   throw new ArgumentException  There is no first letter                 Span lt char gt  a   stackalloc char s Length               s AsSpan 1  CopyTo a Slice 1                a 0    char ToUpper s 0                return new string a                        Edit  There was a typeo  instead of s 0   was a 0  - this results with cupying same  empty value to the allocated Span a

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There seems to be a lot of complexity here when all you need is            lt summary gt          Returns the input string with the first character converted to uppercase if a letter          lt  summary gt           lt remarks gt Null input returns null lt  remarks gt      public static string FirstLetterToUpperCase this string s                if  string IsNullOrWhiteSpace s               return s           return char ToUpper s 0     s Substring 1           Noteworthy points    Its an extension method  If the input is null  empty or whitespace the input is returned as is  String IsNullOrWhiteSpace was introduced with  NET Framework 4  This won t work with older frameworks

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Expanding on Carlos  question above  if you want to capitalize multiple sentences you may use this code             lt summary gt          Capitalize first letter of every sentence            lt  summary gt           lt param name  inputSting  gt  lt  param gt           lt returns gt  lt  returns gt      public string CapitalizeSentences  string inputSting                string result   string Empty          if   string IsNullOrEmpty inputSting                         string   sentences   inputSting Split                    foreach  string sentence in sentences                                result    string Format    0  1     sentence First   ToString   ToUpper    sentence Substring 1                                      return result

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I found something here http   www dotnetperls com uppercase-first-letter    static string UppercaseFirst string s       Check for empty string  if  string IsNullOrEmpty s         return string Empty       Return char and concat substring  return char ToUpper s 0     s Substring 1       maybe this helps

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string input    red HOUSE   System Text StringBuilder sb   new System Text StringBuilder input    for  int j   0  j  lt  sb Length  j          if   j    0     catches just the first letter         sb j    System Char ToUpper sb j        else    everything else is lower case         sb j    System Char ToLower sb j         Store the new string  string corrected   sb ToString    System Console WriteLine corrected

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Since I happened to be working on this also  and was looking around for any ideas  this is the solution I came to  It uses LINQ  and will be able to capitalize the first letter of a string  even if the first occurrence isn t a letter  Here s the extension method I ended up making   public static string CaptalizeFirstLetter this string data        var chars   data ToCharArray            Find the Index of the first letter     var charac   data First char IsLetter       var i   data IndexOf charac           capitalize that letter     chars i    char ToUpper chars i         return new string chars       I m sure there s a way to optimize or clean this up a little bit

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If performance memory usage is an issue then  this one only creates one  1  StringBuilder and one  1  new String of the same size as the Original string   public static string ToUpperFirst this string str      if   string IsNullOrEmpty  str           StringBuilder sb   new StringBuilder str       sb 0    char ToUpper sb 0         return sb ToString         else return str

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string emp  TENDULKAR   string output  output emp First   ToString   ToUpper     String Join     emp Skip 1   ToLower

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You can use  ToTitleCase method   string s   new CultureInfo  en-US   TextInfo ToTitleCase  red house      result   Red House   this extention method solve every titlecase problem   easy to usage  string str    red house   str ToTitleCase      result   Red house  string str    red house   str ToTitleCase TitleCase All     result   Red House   the Extention method  using System  using System Collections Generic  using System Linq  using System Text  using System Globalization   namespace Test       public static class StringHelper               private static CultureInfo ci   new CultureInfo  en-US              Convert all first latter         public static string ToTitleCase this string str                        str   str ToLower                var strArray   str Split                   if  strArray Length  gt  1                                strArray 0    ci TextInfo ToTitleCase strArray 0                    return string Join      strArray                             return ci TextInfo ToTitleCase str                     public static string ToTitleCase this string str  TitleCase tcase                        str   str ToLower                switch  tcase                                case TitleCase First                      var strArray   str Split                           if  strArray Length  gt  1                                                strArray 0    ci TextInfo ToTitleCase strArray 0                            return string Join      strArray                                             break                  case TitleCase All                      return ci TextInfo ToTitleCase str                   default                      break                            return ci TextInfo ToTitleCase str                        public enum TitleCase               First          All

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I took the fastest method from http   www dotnetperls com uppercase-first-letter and converted to extension method            lt summary gt          Returns the input string with the first character converted to uppercase  or mutates any nulls passed into string Empty          lt  summary gt      public static string FirstLetterToUpperCaseOrConvertNullToEmptyString this string s                if  string IsNullOrEmpty s               return string Empty           char   a   s ToCharArray            a 0    char ToUpper a 0            return new string a           NOTE  The reason using ToCharArray is faster than the alternative char ToUpper s 0     s Substring 1   is that only one string is allocated  whereas the Substring approach allocates a string for the substring  then a second string to compose the final result     EDIT  Here is what this approach looks like  combined with the initial test from CarlosMu  oz accepted answer            lt summary gt          Returns the input string with the first character converted to uppercase          lt  summary gt      public static string FirstLetterToUpperCase this string s                if  string IsNullOrEmpty s               throw new ArgumentException  There is no first letter             char   a   s ToCharArray            a 0    char ToUpper a 0            return new string a

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I think the below method is the best solution      class Program       static string UppercaseWords string value                char   array   value ToCharArray               Handle the first letter in the string          if  array Length  gt   1                        if  char IsLower array 0                                  array 0    char ToUpper array 0                                       Scan through the letters  checking for spaces                 Uppercase the lowercase letters following spaces          for  int i   1  i  lt  array Length  i                          if  array i - 1                                        if  char IsLower array i                                          array i    char ToUpper array i                                                      return new string array              static void Main                    Uppercase words in these strings          const string value1    something in the way           const string value2    dot net PERLS           const string value3    String two three           const string value4     sam                  Compute the uppercase strings          Console WriteLine UppercaseWords value1            Console WriteLine UppercaseWords value2            Console WriteLine UppercaseWords value3            Console WriteLine UppercaseWords value4             Output  Something In The Way Dot Net PERLS String two three  Sam   ref

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This capitalizes this first letter and every letter following a space and lower cases any other letter   public string CapitalizeFirstLetterAfterSpace string input        System Text StringBuilder sb   new System Text StringBuilder input       bool capitalizeNextLetter   true      for int pos   0  pos  lt  sb Length  pos                  if capitalizeNextLetter                        sb pos  System Char ToUpper sb pos                capitalizeNextLetter   false                    else                       sb pos  System Char ToLower sb pos                       if sb pos                             capitalizeNextLetter true

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TextInfo ti   CultureInfo CurrentCulture TextInfo  Console WriteLine ti ToTitleCase inputString

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public string FirstLetterToUpper string str        if  str    null          return null       if  str Length  gt  1          return char ToUpper str 0     str Substring 1        return str ToUpper        Old answer  This makes every first letter to upper case  public string ToTitleCase string str        return CultureInfo CurrentCulture TextInfo ToTitleCase str ToLower

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Use the following code   string  strtest   PRASHANT   strtest First   ToString   ToUpper     strtest Remove 0  1  ToLower

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Here s a way to do it as an extension method   static public string UpperCaseFirstCharacter this string text        if   string IsNullOrEmpty text                 return string Format                0  1                text Substring 0  1  ToUpper                text Substring 1               return text      Can then be called like     yields  This is Brian s test     this is Brian s test   UpperCaseFirstCharacter       And here s some unit tests for it    Test  public void UpperCaseFirstCharacter ZeroLength ReturnsOriginal         string orig           string result   orig UpperCaseFirstCharacter         Assert AreEqual orig  result       Test  public void UpperCaseFirstCharacter SingleCharacter ReturnsCapital         string orig    c       string result   orig UpperCaseFirstCharacter         Assert AreEqual  C   result       Test  public void UpperCaseFirstCharacter StandardInput CapitalizeOnlyFirstLetter         string orig    this is Brian s test        string result   orig UpperCaseFirstCharacter         Assert AreEqual  This is Brian s test    result

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send a string to this function  it will first check string is empty or null  if not string will be all lower chars  then return first char of string upper rest of them lower   string FirstUpper string s                   Check for empty string          if  string IsNullOrEmpty s                         return string Empty                    s   s ToLower               Return char and concat substring          return char ToUpper s 0     s Substring 1

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Possible solution to resolve your problem        public static string FirstToUpper this string lowerWord              if  string IsNullOrWhiteSpace lowerWord     string IsNullOrEmpty lowerWord               return lowerWord         return new StringBuilder lowerWord Substring 0  1  ToUpper                      Append lowerWord Substring 1                     ToString

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Easiest way to Capitalize firs letter is   1- Using Sytem Globalization        Creates a TextInfo based on the  en-US  culture    TextInfo myTI   new CultureInfo  en-US  false      myTI ToTitleCase textboxname Text

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I use this to correct names  It basically works on the concept of changing a character to uppercase if it follows a specific pattern  in this case I ve gone for space  dash of  Mc    private String CorrectName String name                        List lt String gt  StringsToCapitalizeAfter   new List lt String gt            -    Mc                 StringBuilder NameBuilder   new StringBuilder                name Select c   gt  c ToString    ToList   ForEach c   gt                                c   c ToLower                    StringsToCapitalizeAfter ForEach s   gt                                        if String IsNullOrEmpty NameBuilder ToString       NameBuilder ToString   EndsWith s                                                 c   c ToUpper                                                              NameBuilder Append c                               return NameBuilder ToString

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FluentSharp has the lowerCaseFirstLetter method which does this  https   github com o2platform FluentSharp blob 700dc35759db8e2164771a71f73a801aa9379074 FluentSharp CoreLib ExtensionMethods System String ExtensionMethods cs L575

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It s fastest way   public static unsafe void ToUpperFirst this string str        if  str    null  return      fixed  char  ptr   str            ptr   char ToUpper  ptr       Without changing original string   public static unsafe string ToUpperFirst this string str        if  str    null  return null      string ret   string Copy str       fixed  char  ptr   ret            ptr   char ToUpper  ptr       return ret

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With this method you can upper the first char of every word   Example  HeLlo wOrld        Hello World   public static string FirstCharToUpper string input        if  String IsNullOrEmpty input           throw new ArgumentException  Error        return string Join      input Split      Select d   gt  d First   ToString   ToUpper      d ToLower   Substring 1

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I wanted to provide a  MAXIMUM PERFORMANCE  answer   In my mind  a  MAXIMUM PERFORMANCE  answer catches all scenarios and provides the answer to the question accounting for those scenarios   So  here is my answer   With these reasons    IsNullOrWhiteSpace accounts for strings that are just spaces or null empty   Trim   removes whitespace from the front and back of the string     First   takes the first character of an ienumerable  or string   We should check to see if it is a letter that can should be uppercase  We then add the rest of the string  only if the length indicates we should  By  Net best practice  we should provide a culture under System Globalization CultureInfo  Providing them as optional parameters makes this method totally reusable  without having to type the chosen culture every time   public static string capString string instring  string culture    en-US   bool useSystem   false        string outstring      if  String IsNullOrWhiteSpace instring                 return               instring   instring Trim        char thisletter   instring First        if   char IsLetter thisletter                 return instring               outstring   thisletter ToString   ToUpper new CultureInfo culture  useSystem        if  instring Length  gt  1                outstring    instring Substring 1             return outstring

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Try this   static public string UpperCaseFirstCharacter this string text        return Regex Replace text     a-z    m   gt  m Value ToUpper

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As BobBeechey suggests in his response to this question  the following code will work for this   private void txt fname TextChanged object sender  EventArgs e        char   c   txt fname Text ToCharArray        int j      for  j   0  j  lt  txt fname Text Length  j                  if  j  0  c j  c j  ToString   ToUpper   0           else c j    c j  ToString   ToLower   0             txt fname Text   new string c        txt fname Select txt fname Text Length  1

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For the first letter  with error checking   public string CapitalizeFirstLetter string s        if  String IsNullOrEmpty s           return s      if  s Length    1          return s ToUpper        return s Remove 1  ToUpper     s Substring 1       And here s the same as a handy extension  public static string CapitalizeFirstLetter this string s            if  String IsNullOrEmpty s   return s      if  s Length    1  return s ToUpper        return s Remove 1  ToUpper     s Substring 1

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This will do it although it will also make sure that there are no errant capitals that are not at the beginning of the word   public string string s    System Globalization CultureInfo c   new System Globalization CultureInfo  en-us   false  System Globalization TextInfo t   c TextInfo   return t ToTitleCase s

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If you only care about first letter being capitalized and  it does not matter the rest of the string you can just select the first character  make it upper case and concatenate it with the rest of the string without the original first character   String word   red house   word   word 0  ToString   ToUpper     word Substring 1  word length -1     result  word    Red house    We need to convert the first character ToString   because we are reading it as a Char array  and Char type does not have ToUpper   method

[c#] Make first letter of a string upper case (with maximum performance)

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