foreach with index

Question

Is there a C  equivalent of Python s enumerate   and Ruby s each with index

User · Answer

Aside from the LINQ answers already given, I have a "SmartEnumerable" class which allows you to get the index and the "first/last"-ness. It's a bit ugly in terms of syntax, but you may find it useful.

We can probably improve the type inference using a static method in a nongeneric type, and implicit typing will help too.

User · Answer

No  there is not   As other people have shown  there are ways to simulate Ruby s behavior  But it is possible to have a type that implements IEnumerable that does not expose an index

User · Answer

I keep this extension method around for this   public static void Each lt T gt  this IEnumerable lt T gt  ie  Action lt T  int gt  action        var i   0      foreach  var e in ie  action e  i         And use it like so   var strings   new List lt string gt     strings Each  str  n    gt           hooray       Or to allow for break-like behaviour   public static bool Each lt T gt  this IEnumerable lt T gt  ie  Func lt T  int  bool gt  action        int i   0      foreach  T e in ie  if   action e  i     return false      return true     var strings   new List lt string gt       a    b    c      bool iteratedAll   strings Each   str  n     gt        if  str     b   return false      return true

User · Answer

You can do the following  foreach  var it in someCollection Select  x  i    gt  new   Value   x  Index   i           if  it Index  gt  SomeNumber               This will create an anonymous type value for every entry in the collection  It will have two properties   Value  with the original value in the collection Index  with the index within the collection

User · Answer

This is your collection  var values   new    6  2  8  45  9  3  0     Make a range of indexes for this collection  var indexes   Enumerable Range 0  values Length  ToList      Use the range to iterate with index  indexes ForEach i   gt  values i     i   indexes ForEach i   gt  Console Write    0      1    i  values i

User · Answer

I just figured out interesting solution   public class DepthAware lt T gt    IEnumerable lt T gt        private readonly IEnumerable lt T gt  source       public DepthAware IEnumerable lt T gt  source                this source   source          this Depth   0             public int Depth   get  private set         private IEnumerable lt T gt  GetItems                 foreach  var item in source                        yield return item                this Depth                       public IEnumerator lt T gt  GetEnumerator                 return GetItems   GetEnumerator               IEnumerator IEnumerable GetEnumerator                 return GetEnumerator                Generic type leverage and extension invoking public static class DepthAware       public static DepthAware lt T gt  AsDepthAware lt T gt  this IEnumerable lt T gt  source                return new DepthAware lt T gt  source              public static DepthAware lt T gt  New lt T gt  IEnumerable lt T gt  source                return new DepthAware lt T gt  source             Usage   var chars   new     a    b    c    d    e    f    g   AsDepthAware     foreach  var item in chars        Console WriteLine  Char   0   depth   1    item  chars Depth

User · Answer

I like being able to use foreach  so I made an extension method and a structure   public struct EnumeratedInstance lt T gt        public long cnt      public T item     public static IEnumerable lt EnumeratedInstance lt T gt  gt  Enumerate lt T gt  this IEnumerable lt T gt  collection        long counter   0      foreach  var item in collection                yield return new EnumeratedInstance lt T gt                        cnt   counter              item   item                    counter              and an example use   foreach  var ii in new string      a    b    c    Enumerate          Console WriteLine ii item   ii cnt       One nice thing is that if you are used to the Python syntax  you can still use it   foreach  var ii in Enumerate new string      a    b    c

User · Answer

It depends on the class you are using   Dictionary lt  Of  lt  TKey  TValue     Class For Example Support This  The Dictionary lt  Of  lt  TKey  TValue     generic class provides a mapping from a set of keys to a set of values    For purposes of enumeration  each item in the dictionary is treated as a KeyValuePair lt  Of  lt  TKey  TValue     structure representing a value and its key  The order in which the items are returned is undefined   foreach  KeyValuePair kvp in myDictionary

User · Answer

My solution involves a simple Pair class I created for general utility  and which is operationally essentially the same as the framework class KeyValuePair   Then I created a couple extension functions for IEnumerable called Ordinate  from the set theory term  ordinal     These functions will return for each item a Pair object containing the index  and the item itself   public static IEnumerable lt Pair lt Int32  X gt  gt  Ordinate lt X gt  this IEnumerable lt X gt  lhs        return lhs Ordinate 0      public static IEnumerable lt Pair lt Int32  X gt  gt  Ordinate lt X gt  this IEnumerable lt X gt  lhs  Int32 initial        Int32 index   initial - 1       return lhs Select x   gt  new Pair lt Int32  X gt    index  x

User · Answer

The C  foreach doesn t have a built in index   You ll need to add an integer outside the foreach loop and increment it each time    int i   -1  foreach  Widget w in widgets       i          do something     Alternatively  you could use a standard for loop as follows   for  int i   0  i  lt  widgets Length  i         w   widgets i         do something

[c#] foreach with index

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