getting index of elements by from a list

Question

Suppose I have a list of objects called TheListOfMyObjects . In that list, there's an object with a property that matches a value: MyObject.TheProperty = SomeValue .

How can I get the previous 3 objects and the next 3 objects from within this list?

Note that if the object that matches SomeValue is in first position then I'd need the 3 objects in position 2-5 and the 3 objects in the last 3 positions for a total of 6 objects.

Thanks for your suggestions.

Answer 1

Try this:

var theObj = TheListOfMyObjects.First(x => x.TheProperty == someValue);
var index = TheListOfMyObjects.IndexOf(theObj);
//and from there it's obvious.

In case there's a chance the list won't contain such an element, use FirstOrDefault and check for null on theObj.

Answer 2

Sorry for the late answer, I had problems with the computer. You don't have to add another list, you can solve edge cases with something like this if you have at least 7 objects in your list:

            MyObject mo = list.FirstOrDefault(x => x.TheProperty.Equals(SomeValue));
            if(mo != null)
            {
                int index = list.IndexOf(mo);
                MyObject moMinus3 = list[(index - 3 + list.Count) % list.Count];
                MyObject moMinus2 = list[(index - 2 + list.Count) % list.Count];
                MyObject moMinus1 = list[(index - 1 + list.Count) % list.Count];
                MyObject mo0 = list[index];
                MyObject moPlus1 = list[(index + 1 + list.Count) % list.Count];
                MyObject moPlus2 = list[(index + 2 + list.Count) % list.Count];
                MyObject moPlus3 = list[(index + 3 + list.Count) % list.Count];
            }