Question

I am trying to do this:

foreach (Settings sets in MySets)
            {
                if (sets.pName == item.SubItems[2].Text)
                {
                    var ss = new SettingsForm(sets);
                    if (ss.ShowDialog() == DialogResult.OK)
                    {
                        if (ss.ResultSave)
                        {
                            sets = ss.getSettings();
                        }
                    }
                    return;
                }
            }

But since the sets spawned variable is readonly, I cant override it.

I would also like to do something like this

foreach (Settings sets in MySets)
{

  if(sets.pName == someName)
     sets.RemoveFromList();
}

How can I accomplish this? Lists have a very nice Add() method, but they forgot the rest 🙁

Answer 1

You can use:

MySets.RemoveAll(sets => sets.pName == someName);

to remove all the items that satisfy a specific condition.

If you want to grab all the items satisfying a condition without touching the original list, you can try:

List<Settings> selectedItems = MySets.FindAll(sets => sets.pName == someName);

foreach loops don’t work here as trying to change the underlying list will cause an exception in the next iteration of the loop. Of course, you can use a for loop and manually index the list. However, you should be very careful not to miss any items in the process of removing an item from the list (since the index of all the following items will get decremented if an element is removed):

for (int i = 0; i < MySets.Count; ++i) {
   var sets = MySets[i]; // simulate `foreach` current variable

   // The rest of the code will be pretty much unchanged.
   // Now, you can set `MySets[i]` to a new object if you wish so:
   //   MySets[i] = new Settings(); 
   //
   // If you need to remove the item from a list and need to continue processing
   // the next item:   (decrementing the index var is important here)
   //   MySets.RemoveAt(i--);
   //   continue;

   if (sets.pName == item.SubItems[2].Text)
   {
      var ss = new SettingsForm(sets);
      if (ss.ShowDialog() == DialogResult.OK)
      {
         if (ss.ResultSave)
         {
            // Assigning to `sets` is not useful. Directly modify the list:
            MySets[i] = ss.getSettings();
         }
      }
      return;
   }
}