Concat all strings inside a List string using LINQ

Question

Is there any easy LINQ expression to concatenate my entire List lt string gt  collection items to a single string with a delimiter character   What if the collection is of custom objects instead of string  Imagine I need to concatenate on object Name

User · Answer

You can simply use   List lt string gt  items   new List lt string gt       foo    boo    john    doe      Console WriteLine string Join      items      Happy coding

User · Answer

String Join delimiter  list    is sufficient

User · Answer

You can use Aggregate  to concatenate the strings into a single  character separated string but will throw an Invalid Operation Exception if the collection is empty    You can use Aggregate function with a seed string   var seed   string Empty  var seperator         var cars   new List lt string gt       Ford    McLaren Senna    Aston Martin Vanquish     var carAggregate   cars Aggregate seed                   partialPhrase  word    gt     partialPhrase  seperator  word    TrimStart         you can use string Join doesn   t care if you pass it an empty collection   var seperator         var cars   new List lt string gt       Ford    McLaren Senna    Aston Martin Vanquish     var carJoin   string Join seperator  cars

User · Answer

using System Linq   public class Person     string FirstName   get  set      string LastName   get  set       List lt Person gt  persons   new List lt Person gt      string listOfPersons   string Join      persons Select p   gt  p FirstName

User · Answer

I have done this using LINQ   var oCSP    from P in db Products select new   P ProductName      string joinedString   string Join      oCSP Select p   gt  p ProductName

User · Answer

Put String Join into an extension method  Here is the version I use  which is less verbose than Jordaos version   returns empty string  quot  quot  when list is empty  Aggregate would throw exception instead  probably better performance than Aggregate is easier to read when combined with other LINQ methods than a pure String Join    Usage var myStrings   new List lt string gt       quot a quot    quot b quot    quot c quot     var joinedStrings   myStrings Join  quot   quot         quot a b c quot   Extensionmethods class public static class ExtensionMethods       public static string Join this IEnumerable lt string gt  texts  string separator                return String Join separator  texts

User · Answer

Good question  I ve been using  List lt string gt  myStrings   new List lt string gt    ours    mine    yours    string joinedString   string Join       myStrings ToArray       It s not LINQ  but it works

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This is for a string array   string Join delimiter  array     This is for a List lt string gt    string Join delimiter  list ToArray       And this is for a list of custom objects   string Join delimiter  list Select i   gt  i Boo  ToArray

User · Answer

List lt string gt  strings   new List lt string gt       ABC    DEF    GHI     string s   strings Aggregate  a  b    gt  a         b

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By using LINQ  this should work   string delimiter        List lt string gt  items   new List lt string gt       foo    boo    john    doe     Console WriteLine items Aggregate  i  j    gt  i   delimiter   j      class description   public class Foo       public string Boo   get  set        Usage   class Program       static void Main string   args                string delimiter                List lt Foo gt  items   new List lt Foo gt      new Foo   Boo    ABC     new Foo   Boo    DEF                 new Foo   Boo    GHI     new Foo   Boo    JKL                Console WriteLine items Aggregate  i  j    gt  new Foo Boo    i Boo   delimiter   j Boo    Boo           Console ReadKey               And here is my best     items Select i   gt  i Boo  Aggregate  i  j    gt  i   delimiter   j

User · Answer

I think that if you define the logic in an extension method the code will be much more readable   public static class EnumerableExtensions      public static string Join lt T gt  this IEnumerable lt T gt  self  string separator          return String Join separator  self Select e   gt  e ToString    ToArray               public class Person       public string FirstName   get  set        public string LastName   get  set        public override string ToString         return string Format   0   1    FirstName  LastName                    List lt Person gt  people   new List lt Person gt            string fullNames   people Join        string lastNames   people Select p   gt  p LastName  Join

[c#] Concat all strings inside a List<string> using LINQ

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