Add element to list before specific element

Question

I have a list of items, lets say 100 items. I need to add another element before the existing element that matches my condition. What is the fastest way and the most performance optimized to do this? ie.:

foreach (var i in myList)
{
    if (myList[i].value == "myValue")
    {
        myList[i-1] add ("someOtherValue")
    }
}

Maybe i should use other container?

Answer 1

First you could find the index of your item using FindIndex method:

var index = myList.FindIndex(x => x.value == "myvalue");

Then Insert at the right point:

myList.Insert(index,newItem);

Note that inserting at a given index pushes everything else forward (think about finding your item at index 0).