C# List insert in foreach [closed]

Question

I have the following loop:

List<Reminders> reminds = new List<Reminders>();
//...
foreach (Reminders remind in reminds)
{
    //....
    reminds.Insert(id, new Reminders() { Title = remind.Title, Content = remind.Content, Checked = true });
}

However, an error occurs in the foreach loop.

foreach (Reminders remind in reminds)

If I remove the reminds.Insert statement, the error no longer occurs. I'm trying to update some entires inside of the foreach loop. What's causing the error?

Answer 1

Change your Code to this:

List<Reminders> reminds = new List<Reminders>();
...
foreach (Reminders remind in reminds.ToList())
{
    ....
    reminds.Insert(id, new Reminders() { Title = remind.Title, Content = remind.Content, Checked = true });
}

Please note the .ToList() behind reminds.

Explanation: You are not allowed to modify a collection while it is enumerated in an foreach. The .ToList() will create another temporary collection which will be constrant during the foreach loop.