Question

I have to delete some rows from a data table. I’ve heard that it is not ok to change a collection while iterating through it. So instead of a for loop in which I check if a row meets the demands for deletion and then mark it as deleted, I should first iterate through the data table and add all of the rows in a list, then iterate through the list and mark the rows for deletions. What are the reasons for this, and what alternatives do I have (instead of using the rows list I mean)?.

Answer 1

You can remove elements from a collection if you use a simple for loop.

Take a look at this example:

        var l = new List<int>();          l.Add(0);         l.Add(1);         l.Add(2);         l.Add(3);         l.Add(4);         l.Add(5);         l.Add(6);          for (int i = 0; i < l.Count; i++)         {             if (l[i] % 2 == 0)             {                 l.RemoveAt(i);                 i--;             }         }          foreach (var i in l)         {             Console.WriteLine(i);         }