Console WriteLine and generic List

Question

I frequently find myself writing code like this   List lt int gt  list   new List lt int gt    1  3  5    foreach  int i in list        Console Write   0  t   i ToString       Console WriteLine      Better would be something like this   List lt int gt  list   new List lt int gt    1  3  5    Console WriteLine   0  t   list     I suspect there s some clever way of doing this  but I don t see it  Does anybody have a better solution than the first block

User · Answer

new List lt int gt    1  3  5   ForEach Console WriteLine

User · Answer

List lt int gt  list   new List lt int gt    1  3  5    list ForEach x   gt  Console WriteLine x      Edit  Dammit  took too long to open visual studio to test it

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Do this   list ForEach i   gt  Console Write   0  t   i        EDIT  To others that have responded - he wants them all on the same line  with tabs between them

User · Answer

List lt int gt  a   new List lt int gt      1  2  3  4  5            a ForEach p   gt  Console WriteLine p      edit  ahhh he beat me to it

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public static void WriteLine this List lt int gt  theList      foreach  int i in list          Console Write   0  t   t ToString           Console WriteLine        Then  later     list WriteLine

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Also you can do join   var qwe   new List lt int gt   5  2  3  8   Console WriteLine string Join   t   qwe

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If there is a piece of code that you repeat all the time according to Don t Repeat Yourself you should put it in your own library and call that  With that in mind there are 2 aspects to getting the right answer here  The first is clarity and brevity in the code that calls the library function  The second is the performance implications of foreach    First let s think about the clarity and brevity in the calling code    You can do foreach in a number of ways    for loop foreach loop Collection ForEach   Out of all the ways to do a foreach List ForEach with a lamba is the clearest and briefest   list ForEach i   gt  Console Write   0  t   i      So at this stage it may look like the List ForEach is the way to go  However what s the performance of this  It s true that in this case the time to write to the console will govern the performance of the code  When we know something about performance of a particular language feature we should certainly at least consider it   According to Duston Campbell s performance measurements of foreach the fastest way of iterating the list under optimised code is using a for loop without a call to List Count   The for loop however is a verbose construct  It s also seen as a very iterative way of doing things which doesn t match with the current trend towards functional idioms   So can we get brevity  clarity and performance  We can by using an extension method  In an ideal world we would create an extension method on Console that takes a list and writes it with a delimiter  We can t do this because Console is a static class and extension methods only work on instances of classes  Instead we need to put the extension method on the list itself  as per David B s suggestion    public static void WriteLine this List lt int gt  theList      foreach  int i in list          Console Write   0  t   t ToString           Console WriteLine        This code is going to used in many places so we should carry out the following improvements    Instead of using foreach we should use the fastest way of iterating the collection which is a for loop with a cached count   Currently only List can be passed as an argument  As a library function we can generalise it through a small amount of effort   Using List limits us to just Lists  Using IList allows this code to work with Arrays too  Since the extension method will be on an IList we need to change the name to make it clearer what we are writing to    Here s how the code for the function would look   public static void WriteToConsole lt T gt  this IList lt T gt  collection        int count   collection Count        for int i   0   i  lt  count    i                Console Write   0  t   collection i  ToString    delimiter             Console WriteLine        We can improve this even further by allowing the client to pass in the delimiter  We could then provide a second function that writes to console with the standard delimiter like this   public static void WriteToConsole lt T gt  this IList lt T gt  collection        WriteToConsole lt T gt  collection    t       public static void WriteToConsole lt T gt  this IList lt T gt  collection  string delimiter        int count   collection Count        for int i   0   i  lt  count    i                 Console Write   0  1    collection i  ToString    delimiter             Console WriteLine        So now  given that we want a brief  clear performant way of writing lists to the console we have one  Here is entire source code including a demonstration of using the the library function   using System  using System Collections Generic  using System Linq   namespace ConsoleWritelineTest       public static class Extensions               public static void WriteToConsole lt T gt  this IList lt T gt  collection                        WriteToConsole lt T gt  collection    t                       public static void WriteToConsole lt T gt  this IList lt T gt  collection  string delimiter                        int count   collection Count                for int i   0   i  lt  count    i                                Console Write   0  1    collection i  ToString    delimiter                             Console WriteLine                         internal class Foo               override public string ToString                         return  FooClass                        internal class Program                static void Main string   args                        var myIntList   new List lt int gt   1  2  3  4  5               var myDoubleList   new List lt double gt   1 1  2 2  3 3  4 4               var myDoubleArray   new Double    12 3  12 4  12 5  12 6               var myFooList   new List lt Foo gt   new Foo    new Foo    new Foo                    Using the standard delimiter  t             myIntList WriteToConsole                myDoubleList WriteToConsole                myDoubleArray WriteToConsole                myFooList WriteToConsole                   Using our own delimiter               myIntList WriteToConsole                   Console Read                                                                                 You might think that this should be the end of the answer  However there is a further piece of generalisation that can be done  It s not clear from fatcat s question if he is always writing to the console  Perhaps something else is to be done in the foreach  In that case Jason Bunting s answer is going to give that generality  Here is his answer again   list ForEach i   gt  Console Write   0  t   i      That is unless we make one more refinement to our extension methods and add FastForEach as below   public static void FastForEach lt T gt  this IList lt T gt  collection  Action lt T gt  actionToPerform                int count   collection Count            for  int i   0  i  lt  count    i                        actionToPerform collection i                          Console WriteLine            This allows us to execute any arbitrary code against every element in the collection using the fastest possible iteration method   We can even change the WriteToConsole function to use FastForEach  public static void WriteToConsole lt T gt  this IList lt T gt  collection  string delimiter         collection FastForEach item   gt  Console Write   0  1    item ToString    delimiter        So now the entire source code  including an example usage of FastForEach is   using System  using System Collections Generic  using System Linq   namespace ConsoleWritelineTest       public static class Extensions               public static void WriteToConsole lt T gt  this IList lt T gt  collection                        WriteToConsole lt T gt  collection    t                       public static void WriteToConsole lt T gt  this IList lt T gt  collection  string delimiter                         collection FastForEach item   gt  Console Write   0  1    item ToString    delimiter                       public static void FastForEach lt T gt  this IList lt T gt  collection  Action lt T gt  actionToPerform                        int count   collection Count                for  int i   0  i  lt  count    i                                actionToPerform collection i                                  Console WriteLine                         internal class Foo               override public string ToString                         return  FooClass                        internal class Program                static void Main string   args                        var myIntList   new List lt int gt   1  2  3  4  5               var myDoubleList   new List lt double gt   1 1  2 2  3 3  4 4               var myDoubleArray   new Double    12 3  12 4  12 5  12 6               var myFooList   new List lt Foo gt   new Foo    new Foo    new Foo                     Using the standard delimiter  t             myIntList WriteToConsole                myDoubleList WriteToConsole                myDoubleArray WriteToConsole                myFooList WriteToConsole                    Using our own delimiter               myIntList WriteToConsole                       What if we want to write them to separate lines              myIntList FastForEach item   gt  Console WriteLine item ToString                  Console Read

User · Answer

A different approach  just for kicks   Console WriteLine string Join   t   list

User · Answer

list ForEach x  gt Console WriteLine x

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