Safely Removing DataRow In ForEach

Even though DataRow.Delete doesn't modify the state of the collection, Microsoft documentation states that you shouldn't call it while iterating over the collection:

Neither Delete nor Remove should be called in a foreach loop while iterating through a DataRowCollection object. Delete nor Remove modify the state of the collection.

The best solution is usually to create a separate collection (e.g. a List<DataRow>) of items you want to remove, and then remove them after you've finished iterating.

This is also the solution for situations where you want to remove items from a collection, as most collections in .NET don't allow you to change the contents of the collection while you're iterating over it.

Safest way - use for loop

for (int i = datatable.Rows.Count - 1; i >= 0; i--) 
{
    if (true)
    {
        datatable.Rows[i].Delete();
    }
}

Don't forget to AcceptChanges to remove all marked rows:

datatable.AcceptChanges();