How do I foreach through a two-dimensional array

Question

I ve got a two-dimensional array   string    table                               aa    aaa                               bb    bbb                            And I d like to foreach through it like this   foreach  string   row in table        Console WriteLine row 0          row 1        But  I get the error      Can t convert type string to string     Is there a way I can achieve what I want  i e  iterate through the first dimension of the array with the iterator variable returning me the one-dimensional array for that row

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Here s a simple extension method that returns each row as an IEnumerable lt T gt   This has the advantage of not using any extra memory   public static class Array2dExt       public static IEnumerable lt IEnumerable lt T gt  gt  Rows lt T gt  this T    array                for  int r   array GetLowerBound 0   r  lt   array GetUpperBound 0     r              yield return row array  r              static IEnumerable lt T gt  row lt T gt  T    array  int r                for  int c   array GetLowerBound 1   c  lt   array GetUpperBound 1     c              yield return array r  c             Sample usage   static void Main         string    siblings        Mike    Amy        Mary    Albert       Fred    Harry           foreach  var row in siblings Rows            Console WriteLine       string Join       row

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string     table

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Multidimensional arrays aren t enumerable  Just iterate the good old-fashioned way   for  int i   0  i  lt  table GetLength 0   i          Console WriteLine table i  0          table i  1

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string     languages   new string 2                 languages 0    new string 2               languages 1    new string 3      inserting data into double dimensional arrays              for  int i   0  i  lt  2  i                                  languages 0  i     Jagged  i ToString                              for  int j   0  j  lt  3  j                                  languages 1  j     Jag  j ToString                      doing foreach through 2 dimensional arrays  foreach  string   s in languages                                foreach  string a in s                                        Console WriteLine a

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I m not a big fan of this method because of the memory usage involved  but if you use the arrays it produces  it isn t such a waste   public static void ForEachRow lt T gt  this T    list  Action lt int  T   gt  action        var len   list GetLength 0       var sub   list GetLength 1        T   e      int i  j       for  i   0  i  lt  len  i                  e   new T sub            for  j   0  j  lt  sub  j                          e j    list i  j                      action i  e             Implementation   var list   new    0x0  0x1  0x2  0x4  0x8    list ForEachRow  i  row    gt        for  var j   0  j  lt  row Length  j                  Console WriteLine    0   1     2    i  j  row j                The other solution I found is less memory intensive  but will use more CPU  especially when the dimensions of the arrays  entries are larger   public static void ForEachRow lt T gt  this T    list  Action lt int  IEnumerable lt T gt  gt  action        var len   list GetLength 0       var sub   list GetLength 1        int i  j      IEnumerable lt T gt  e       for  i   0  i  lt  len  i                  e   Enumerable Empty lt T gt              for  j   0  j  lt  sub  j                          e   e Concat AsEnumerable list i  j                        action i  e            private static IEnumerable lt T gt  AsEnumerable lt T gt  T add        yield return add      Implementation   var list   new    0x0  0x1  0x2  0x4  0x8    list ForEachRow  i  row    gt        var j   0       forrach  var o in row                Console WriteLine    0   1     2    i  j  o              j              As a whole  I find the first option to be more intuitive  especially if you want to access the produced array by its indexer   At the end of the day  this is all just eye candy  neither methods should really be used in favour of directly accessing the source array   for  var i   0  i  lt  list GetLength 0   i          foreach  var j   0  j  lt  list GetLength 1   j                  Console WriteLine    0   1     2    i  j  list i  j

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I try this  I hope to help  It work with   static void Main                 string    matrix                                       aa    aaa                                       bb    bbb                                          int index   0          foreach  string element in matrix                        if  index  lt  matrix GetLength 1                                 Console Write element                   if  index  lt   matrix GetLength 1  - 1                                         Console Write                                         index                              if  index    matrix GetLength 1                                 Console Write   n                    index   0

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UPDATE  I had some time on my hands  so     I went ahead and fleshed out this idea  See below for the code     Here s a bit of a crazy answer   You could do what you re looking for -- essentially treat a two-dimensional array as a table with rows -- by writing a static method  perhaps an extension method  that takes a T    and returns an IEnumerable lt T   gt   This would require copying each  row  of the underlying table into a new array  though   A perhaps better  though more involved  approach would be to actually write a class that implements IList lt T gt  as a wrapper around a single  row  of a two-dimensional array  you would probably set IsReadOnly to true and just implement the getter for the this int  property and probably Count and GetEnumerator  everything else could throw a NotSupportedException   Then your static extension method could return an IEnumerable lt IList lt T gt  gt  and provide deferred execution   That way you could write code pretty much like what you have   foreach  IList lt string gt  row in table GetRows       or something       Console WriteLine row 0          row 1        Just a thought     Implementation suggestion   public static class ArrayTableHelper       public static IEnumerable lt IList lt T gt  gt  GetRows lt T gt  this T    table            for  int i   0  i  lt  table GetLength 0     i              yield return new ArrayTableRow lt T gt  table  i              private class ArrayTableRow lt T gt    IList lt T gt            private readonly T     table          private readonly int  count          private readonly int  rowIndex           public ArrayTableRow T    table  int rowIndex                if  table    null                  throw new ArgumentNullException  table                 if  rowIndex  lt  0    rowIndex  gt   table GetLength 0                   throw new ArgumentOutOfRangeException  rowIndex                  table   table               count    table GetLength 1                rowIndex   rowIndex                        I didn t implement the setter below             but you easily COULD  and then set IsReadOnly to false           public T this int index                get   return  table  rowIndex  index                 set   throw new NotImplementedException                         public int Count               get   return  count                       bool ICollection lt T gt  IsReadOnly               get   return true                       public IEnumerator lt T gt  GetEnumerator                 for  int i   0  i  lt   count    i                  yield return this i                         omitted remaining IList lt T gt  members for brevity             you actually could implement IndexOf  Contains  etc             quite easily  though              now I think I should give StackOverflow a break for the rest of the day

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It depends on how you define your multi-dimensional array  Here are two options   using System  using System Collections Generic  using System Linq   namespace ConsoleApplication2       class Program               static void Main string   args                           First             string    arr1                               aa    aaa                               bb    bbb                                          Second             string     arr2   new                     new      aa    aaa                     new      bb    bbb                                   Iterate through first             for  int x   0  x  lt   arr1 GetUpperBound 0   x                    for  int y   0  y  lt   arr1 GetUpperBound 1   y                        Console Write arr1 x  y                        Console WriteLine Environment NewLine                   Iterate through second second             foreach  string   entry in arr2                  foreach  string element in entry                      Console Write element                       Console WriteLine Environment NewLine               Console WriteLine  Press any key to finish                Console ReadKey

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Using LINQ you can do it like this   var table enum   table         Convert to IEnumerable lt string gt       OfType lt string gt            Create anonymous type where Index1 and Index2        reflect the indices of the 2-dim  array      Select   string   index    gt  new           Index1     index   2           Index2     index   2        I added this only for completeness         Value    string                Group by Index1  which generates IEnmurable lt string gt  for all Index1 values      GroupBy v   gt  v Index1          Convert all Groups of anonymous type to String-Arrays      Select group   gt  group Select v   gt  v Value  ToArray         Now you can use the foreach-Loop as you planned foreach string   str arr in table enum                   This way it is also possible to use the foreach for looping through the columns instead of the rows by using Index2 in the GroupBy instead of Index 1  If you don t know the dimension of your array then you have to use the GetLength   method to determine the dimension and use that value in the quotient

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As others have suggested  you could use nested for-loops or redeclare your multidimensional array as a jagged one   However  I think it s worth pointing out that multidimensional arrays are enumerable  just not in the way that you want   For example   string    table                              aa    aaa                              bb    bbb                          foreach  string s in table        Console WriteLine s         Output is    aa   aaa   bb   bbb

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Remember that a multi-dimensional array is like a table   You don t have an x element and a y element for each entry  you have a string at  for instance  table 1 2     So  each entry is still only one string  in your example   it s just an entry at a specific x y value   So  to get both entries at table 1  x   you d do a nested for loop   Something like the following  not tested  but should be close   for  int x   0  x  lt  table Length  x          for  int y   0  y  lt  table Length  y    2                Console WriteLine   0   1    table x  y   table x  y   1

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If you define your array like this  string     table   new string                              new string      quot aa quot    quot aaa quot                            new string     quot bb quot    quot bbb quot        Then you can use a foreach loop on it

[c#] How do I 'foreach' through a two-dimensional array?

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