Get current index from foreach loop

Question

Using C  and Silverlight  How do I get the index of the current item in the list   Code   IEnumerable list   DataGridDetail ItemsSource as IEnumerable  List lt string gt  lstFile   new List lt string gt       foreach  var row in list      bool IsChecked    bool   CheckBox DataGridDetail Columns 0  GetCellContent row   IsChecked    if  IsChecked              Here I want to get the index or current row from the list                             How to achieve this

User · Accepted Answer

IEnumerable list   DataGridDetail ItemsSource as IEnumerable  List lt string gt  lstFile   new List lt string gt      int i   0  foreach  var row in list    bool IsChecked    bool   CheckBox DataGridDetail Columns 0  GetCellContent row   IsChecked  if  IsChecked      MessageBox show i   --Here i want to get the index or current row from the list                          i

User · Answer

You can t  because IEnumerable doesn t have an index at all    if you are sure your enumerable has less than int MaxValue elements  or long MaxValue if you use a long index   you can    Don t use foreach  and use a for loop  converting your IEnumerable to a generic enumerable first   var genericList   list Cast lt object gt     for int i   0  i  lt  genericList Count      i       var row   genericList ElementAt i                    Have an external index   int i   0  foreach var row in list                       i     Get the index via Linq   foreach var rowObject in list Cast lt object gt    Select  r  i    gt  new  Row r  Index i        var row   rowObject Row    var i   rowObject Index                        In your case  since your IEnumerable is not a generic one  I d rather use the foreach with external index  second method     otherwise  you may want to make the Cast lt object gt  outside your loop to convert it to an IEnumerable lt object gt    Your datatype is not clear from the question  but I m assuming object since it s an items source  it could be DataGridRow     you may want to check if it s directly convertible to a generic IEnumerable lt object gt  without having to call Cast lt object gt     but I ll make no such assumptions     All this said   The concept of an  index  is foreign to an IEnumerable  An IEnumerable can be potentially infinite  In your example  you are using the ItemsSource of a DataGrid  so more likely your IEnumerable is just a list of objects  or DataRows   with a finite  and hopefully less than int MaxValue  number of members  but IEnumerable can represent anything that can be enumerated  and an enumeration can potentially never end     Take this example   public static IEnumerable InfiniteEnumerable       var rnd   new Random      while true          yield return rnd Next            So if you do   foreach var row in InfiniteEnumerable                      Your foreach will be infinite  if you used an int  or long  index  you ll eventually overflow it  and unless you use an unchecked context  it ll throw an exception if you keep adding to it  even if you used unchecked  the index would be meaningless also    at some point -when it overflows- the index will be the same for two different values    So  while the examples given work for a typical usage  I d rather not use an index at all if you can avoid it

User · Answer

You have two options here  1  Use for instead for foreach for iteration But in your case the collection is IEnumerable and the upper limit of the collection is unknown so foreach will be the best option  so i prefer to use another integer variable to hold the iteration count  here is the code for that   int i   0     for index foreach  var row in list        bool IsChecked    assign value to this variable     if  IsChecked                      use i value here                           i       will increment i in each iteration

User · Answer

Use Enumerable Select lt TSource  TResult  Method  IEnumerable lt TSource   Func lt TSource  Int32  TResult    list   list Cast lt object gt    Select   v  i    gt  new  Value  v  Index   i     foreach var row in list        bool IsChecked    bool   CheckBox DataGridDetail Columns 0  GetCellContent row Value   IsChecked      row Index

[c#] Get current index from foreach loop

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