Question

I have created a list using:

List<int> foo = new List<int>();

I need to be able to insert values into any index after I create this. If I have

foo[325] = 55;

an ArgumentOutOfRangeException is thrown with the following details:

Index must be within the bounds of the List.
Parameter name: index

What must I do in order to correct this? I could fill the list with dummy values and then access the indices after the list is filled, but that seems like a messy solution.

Answer 1

Maybe a List<> isn’t the correct datatype to use for storage.

If you used a Dictionary<int, int>() you can just maintain the indexes you wish:

Dictionary<int, int> foo = new Dictionary<int, int>();

foo.Add(idx, val);

And to retrieve:

var Value = foo[idx];

If you plan on actually using every single index, you’d be better off doing:

List<int> foo = Enumerable.Range(0, MaxNumber).ToList();

To pre-fill the list.