Converting a generic list to a CSV string

Question

I have a list of integer values  List  and would like to generate a string of comma delimited values  That is all items in the list output to a single comma delimted list   My thoughts    1  pass the list to a method  2  Use stringbuilder to iterate the list and append commas 3  Test the last character and if it s a comma  delete it   What are your thoughts  Is this the best way   How would my code change if I wanted to handle not only integers  my current plan  but strings  longs  doubles  bools  etc  etc  in the future  I guess make it accept a list of any type

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http   cc davelozinski com c-sharp the-fastest-way-to-read-and-process-text-files  This website did some extensive testing about how to write to a file using buffered writer  reading line by line seems to be the best way  using string builder was one of the slowest    I use his techniques a great deal for writing stuff to file it works well

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As the code in the link given by  Frank Create a CSV File from a  NET Generic List there was a little issue of ending every line with a   I modified the code to get rid of it Hope it helps someone        lt summary gt      Creates the CSV from a generic list       lt  summary gt        lt typeparam name  T  gt  lt  typeparam gt        lt param name  list  gt The list  lt  param gt        lt param name  csvNameWithExt  gt Name of CSV  w  path  w  file ext  lt  param gt   public static void CreateCSVFromGenericList lt T gt  List lt T gt  list  string csvCompletePath        if  list    null    list Count    0  return         get type from 0th member     Type t   list 0  GetType        string newLine   Environment NewLine       if   Directory Exists Path GetDirectoryName csvCompletePath    Directory CreateDirectory Path GetDirectoryName csvCompletePath         if   File Exists csvCompletePath   File Create csvCompletePath        using  var sw   new StreamWriter csvCompletePath                   make a new instance of the class name we figured out to get its props         object o   Activator CreateInstance t             gets all properties         PropertyInfo   props   o GetType   GetProperties               foreach of the properties in class above  write out properties           this is the header row         sw Write string Join      props Select d   gt  d Name  ToArray      newLine              this acts as datarow         foreach  T item in list                          this acts as datacolumn             var row   string Join      props Select d   gt  item GetType                                                                GetProperty d Name                                                               GetValue item  null                                                               ToString                                                         ToArray                 sw Write row   newLine

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A general purpose ToCsv   extension method         Supports Int16 32 64  float  double  decimal  and anything supporting ToString   Optional custom join separator Optional custom selector Optional null empty handling specification   Opt   overloads    Usage Examples    123  ToCsv       1 2 3   123  ToCsv           1  2  3  new List lt int gt    1  2  3   ToCsv       1 2 3   new List lt Tuple lt int  string gt  gt          Tuple Create 1   One         Tuple Create 2   Two       ToCsv t   gt  t Item2        One Two     string null  ToCsv      throws exception   string null  ToCsvOpt           string null  ToCsvOpt ReturnNullCsv WhenNull     null   Implementation       lt summary gt      Specifies when ToCsv   should return null   Refer to ToCsv   for IEnumerable T       lt  summary gt  public enum ReturnNullCsv            lt summary gt          Return String Empty when the input list is null or empty           lt  summary gt      Never            lt summary gt          Return null only if input list is null   Return String Empty if list is empty           lt  summary gt      WhenNull            lt summary gt          Return null when the input list is null or empty          lt  summary gt      WhenNullOrEmpty            lt summary gt          Throw if the argument is null          lt  summary gt      ThrowIfNull            lt summary gt      Converts IEnumerable list of values to a comma separated string values       lt  summary gt       lt typeparam name  T  gt  lt  typeparam gt       lt param name  values  gt The values  lt  param gt               lt param name  joinSeparator  gt  lt  param gt       lt returns gt System String  lt  returns gt  public static string ToCsv lt T gt       this IEnumerable lt T gt  values                  string joinSeparator              return ToCsvOpt lt T gt  values  null   selector    ReturnNullCsv ThrowIfNull  joinSeparator           lt summary gt      Converts IEnumerable list of values to a comma separated string values       lt  summary gt       lt typeparam name  T  gt  lt  typeparam gt       lt param name  values  gt The values  lt  param gt       lt param name  selector  gt An optional selector lt  param gt       lt param name  joinSeparator  gt  lt  param gt       lt returns gt System String  lt  returns gt  public static string ToCsv lt T gt       this IEnumerable lt T gt  values      Func lt T  string gt  selector                  string joinSeparator               return ToCsvOpt lt T gt  values  selector  ReturnNullCsv ThrowIfNull  joinSeparator           lt summary gt      Converts IEnumerable list of values to a comma separated string values       lt  summary gt       lt typeparam name  T  gt  lt  typeparam gt       lt param name  values  gt The values  lt  param gt       lt param name  returnNullCsv  gt Return mode  refer to enum ReturnNullCsv   lt  param gt       lt param name  joinSeparator  gt  lt  param gt       lt returns gt System String  lt  returns gt  public static string ToCsvOpt lt T gt       this IEnumerable lt T gt  values      ReturnNullCsv returnNullCsv   ReturnNullCsv Never      string joinSeparator              return ToCsvOpt lt T gt  values  null   selector    returnNullCsv  joinSeparator           lt summary gt      Converts IEnumerable list of values to a comma separated string values       lt  summary gt       lt typeparam name  T  gt  lt  typeparam gt       lt param name  values  gt The values  lt  param gt       lt param name  selector  gt An optional selector lt  param gt       lt param name  returnNullCsv  gt Return mode  refer to enum ReturnNullCsv   lt  param gt       lt param name  joinSeparator  gt  lt  param gt       lt returns gt System String  lt  returns gt  public static string ToCsvOpt lt T gt       this IEnumerable lt T gt  values       Func lt T  string gt  selector      ReturnNullCsv returnNullCsv   ReturnNullCsv Never      string joinSeparator              switch  returnNullCsv                case ReturnNullCsv Never              if   values AnyOpt                    return string Empty              break           case ReturnNullCsv WhenNull              if  values    null                  return null              break           case ReturnNullCsv WhenNullOrEmpty              if   values AnyOpt                    return null              break           case ReturnNullCsv ThrowIfNull              if  values    null                  throw new ArgumentOutOfRangeException  ToCsvOpt was passed a null value with ReturnNullCsv   ThrowIfNull                 break           default              throw new ArgumentOutOfRangeException  returnNullCsv   returnNullCsv   Out of range                if  selector    null                if  typeof T     typeof Int16                  typeof T     typeof Int32                  typeof T     typeof Int64                                            selector    v    gt  Convert ToInt64 v  ToStringInvariant                      else if  typeof T     typeof decimal                         selector    v    gt  Convert ToDecimal v  ToStringInvariant                      else if  typeof T     typeof float                     typeof T     typeof double                         selector    v    gt  Convert ToDouble v  ToString CultureInfo InvariantCulture                     else                       selector    v    gt  v ToString                                     return String Join joinSeparator  values Select v   gt  selector v        public static string ToStringInvariantOpt this Decimal  d        return d HasValue   d Value ToStringInvariant     null     public static string ToStringInvariant this Decimal d        return d ToString CultureInfo InvariantCulture      public static string ToStringInvariantOpt this Int64  l        return l HasValue   l Value ToStringInvariant     null     public static string ToStringInvariant this Int64 l        return l ToString CultureInfo InvariantCulture      public static string ToStringInvariantOpt this Int32  i        return i HasValue   i Value ToStringInvariant     null     public static string ToStringInvariant this Int32 i        return i ToString CultureInfo InvariantCulture      public static string ToStringInvariantOpt this Int16  i        return i HasValue   i Value ToStringInvariant     null     public static string ToStringInvariant this Int16 i        return i ToString CultureInfo InvariantCulture

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If any body wants to convert list of custom class objects instead of list of string then override the ToString method of your class with csv row representation of your class   Public Class MyClass     public int Id get set      public String PropertyA get set      public override string ToString             return this Id        this PropertyA           Then following code can be used to convert this class list to CSV with header column  string csvHeaderRow   String Join      typeof MyClass  GetProperties BindingFlags Public   BindingFlags Instance  Select x   gt  x Name  ToArray lt string gt       Environment NewLine  string csv  csvHeaderRow   String Join Environment NewLine  MyClass Select x   gt  x ToString    ToArray

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Any solution work only if List a list of string   If you have a generic list of your own Objects like list of car  where car has n properties  you must loop the PropertiesInfo of each car object   Look at  http   www csharptocsharp com generate-csv-from-generic-list

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The problem with String Join is that you are not handling the case of a comma already existing in the value  When a comma exists then you surround the value in Quotes and replace all existing Quotes with double Quotes   String Join       this value has a   in it   This one doesn t    This one   does       See CSV Module

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CsvHelper library  is very popular in the Nuget You worth it man  https   github com JoshClose CsvHelper wiki Basics  Using CsvHelper is really easy  It s default settings are setup for the most common scenarios   Here is a little setup data   Actors csv   Id FirstName LastName   1 Arnold Schwarzenegger   2 Matt Damon   3 Christian Bale   Actor cs  custom class object that represents an actor    public class Actor       public int Id   get  set        public string FirstName   get  set        public string LastName   get  set        Reading the CSV file using CsvReader   var csv   new CsvReader  new StreamReader   Actors csv         var actorsList   csv GetRecords     Writing to a CSV file   using  var csv   new CsvWriter  new StreamWriter   Actors csv              csv WriteRecords  actorsList

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You can create an extension method that you can call on any IEnumerable   public static string JoinStrings lt T gt       this IEnumerable lt T gt  values  string separator        var stringValues   values Select item   gt           item    null   string Empty   item ToString          return string Join separator  stringValues ToArray         Then you can just call the method on the original list   string commaSeparated   myList JoinStrings

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It s amazing what the Framework already does for us  List lt int gt  myValues  string csv   String Join  quot   quot   myValues Select x   gt  x ToString    ToArray      For the general case  IEnumerable lt T gt  myList  string csv   String Join  quot   quot   myList Select x   gt  x ToString    ToArray      As you can see  it s effectively no different  Beware that you might need to actually wrap x ToString   in quotes  i e    quot   quot  quot    x ToString      quot   quot  quot   in case x ToString   contains commas  For an interesting read on a slight variant of this  see Comma Quibbling on Eric Lippert s blog  Note  This was written before  NET 4 0 was officially released  Now we can just say IEnumerable lt T gt  sequence  string csv   String Join  quot   quot   sequence    using the overload String Join lt T gt  string  IEnumerable lt T gt    This method will automatically project each element x to x ToString

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Here is my extension method  it returns a string for simplicity but my implementation writes the file to a data lake    It provides for any delimiter  adds quotes to string  in case they contain the delimiter  and deals will nulls and blanks            lt summary gt          A class to hold extension methods for C  Lists           lt  summary gt      public static class ListExtensions                    lt summary gt              Convert a list of Type T to a CSV              lt  summary gt               lt typeparam name  T  gt The type of the object held in the list lt  typeparam gt               lt param name  items  gt The list of items to process lt  param gt               lt param name  delimiter  gt Specify the delimiter  default is   lt  param gt               lt returns gt  lt  returns gt          public static string ToCsv lt T gt  this List lt T gt  items  string delimiter                              Type itemType   typeof T               var props   itemType GetProperties BindingFlags Public   BindingFlags Instance  OrderBy p   gt  p Name                var csv   new StringBuilder                    Write Headers             csv AppendLine string Join delimiter  props Select p   gt  p Name                     Write Rows             foreach  var item in items                                   Write Fields                 csv AppendLine string Join delimiter  props Select p   gt  GetCsvFieldasedOnValue p  item                                 return csv ToString                            lt summary gt              Provide generic and specific handling of fields              lt  summary gt               lt typeparam name  T  gt  lt  typeparam gt               lt param name  p  gt  lt  param gt               lt param name  item  gt  lt  param gt               lt returns gt  lt  returns gt          private static object GetCsvFieldasedOnValue lt T gt  PropertyInfo p  T item                        string value                    try                               value   p GetValue item  null   ToString                    if  value    null  return  NULL       Deal with nulls                 if  value Trim   Length    0  return        Deal with spaces and blanks                     Guard strings with  s  they may contain the delimiter                  if  p PropertyType    typeof string                                         value   string Format     0      value                                               catch  Exception ex                                throw ex                            return value                    Usage       Tab Delimited  TSV   var csv   MyList ToCsv lt MyClass gt    t

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For whatever reason   AliUmair reverted the edit to his answer that fixes his code that doesn t run as is  so here is the working version that doesn t have the file access error and properly handles null object property values        lt summary gt      Creates the CSV from a generic list       lt  summary gt        lt typeparam name  T  gt  lt  typeparam gt        lt param name  list  gt The list  lt  param gt        lt param name  csvNameWithExt  gt Name of CSV  w  path  w  file ext  lt  param gt   public static void CreateCSVFromGenericList lt T gt  List lt T gt  list  string csvCompletePath        if  list    null    list Count    0  return         get type from 0th member     Type t   list 0  GetType        string newLine   Environment NewLine       if   Directory Exists Path GetDirectoryName csvCompletePath    Directory CreateDirectory Path GetDirectoryName csvCompletePath         using  var sw   new StreamWriter csvCompletePath                   make a new instance of the class name we figured out to get its props         object o   Activator CreateInstance t             gets all properties         PropertyInfo   props   o GetType   GetProperties               foreach of the properties in class above  write out properties           this is the header row         sw Write string Join      props Select d   gt  d Name  ToArray      newLine              this acts as datarow         foreach  T item in list                          this acts as datacolumn             var row   string Join      props Select d   gt       item GetType   GetProperty d Name  GetValue item  null   ToString                                                             ToArray                 sw Write row   newLine

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I like a nice simple extension method   public static string ToCsv this List lt string gt  itemList                          return string Join      itemList                Then you can just call the method on the original list   string CsvString   myList ToCsv      Cleaner and easier to read than some of the other suggestions

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in 3 5  i was still able to do this  Its much more simpler and doesnt need lambda   String Join      myList ToArray lt string gt

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I explain it in-depth in this post  I ll just paste the code here with brief descriptions   Here s the method that creates the header row  It uses the property names as column names   private static void CreateHeader lt T gt  List lt T gt  list  StreamWriter sw                PropertyInfo   properties   typeof T  GetProperties            for  int i   0  i  lt  properties Length - 1  i                          sw Write properties i  Name                           var lastProp   properties properties Length - 1  Name          sw Write lastProp   sw NewLine           This method creates all the value rows  private static void CreateRows lt T gt  List lt T gt  list  StreamWriter sw                foreach  var item in list                        PropertyInfo   properties   typeof T  GetProperties                for  int i   0  i  lt  properties Length - 1  i                                  var prop   properties i                   sw Write prop GetValue item                                    var lastProp   properties properties Length - 1               sw Write lastProp GetValue item    sw NewLine                     And here s the method that brings them together and creates the actual file   public static void CreateCSV lt T gt  List lt T gt  list  string filePath                using  StreamWriter sw   new StreamWriter filePath                         CreateHeader list  sw               CreateRows list  sw

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You can use String Join   String Join           Array ConvertAll       list ToArray         element   gt  element ToString

[c#] Converting a generic list to a CSV string

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