<p>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)?.</p>

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);
        }
```
```