Add tiles to both sides of TileMap List in MonoGame

Question

This is what my tile map looks like (red highlighting added for clarity):

My code:

private List<List<int>> _layoutLayer = new List<List<int>>(50); // Layout Layer
private List<List<int>> _trLayer = new List<List<int>>(50); // Transitional Layer
private List<List<int>> _entityLayer = new List<List<int>>(50); // Object Layer
private List<List<int>> _logicLayer = new List<List<int>>(50); // Logic Layer

// To add a tile
if (inputManager.IsMouseHeld(true))
{
    try
    {
        switch (_currentLayer)
        {
            case LayerRepresentation.LayoutLayer:
                _layoutLayer[_gridMouseY][_gridMouseX] = _currentTile;
                break;
            case LayerRepresentation.TransitionalLayer:
                _trLayer[_gridMouseY][_gridMouseX] = _currentTile;
                break;
            case LayerRepresentation.EntityLayer:
                _entityLayer[_gridMouseY][_gridMouseX] = _currentTile;
                break;
            case LayerRepresentation.LogicLayer:
                _logicLayer[_gridMouseY][_gridMouseX] = _currentTile;
                break;
        }
    }
    catch
    {
         // Player clicked outside of map bounds, add specified amount of tiles to map
    }
}

What I need:

When the player clicks outside of map bounds for example on the point A, add the amount of tiles between point A and the map to the map's height. Do the same with point B, but add to the map width instead.

What I've tried:

    // Inside the above catch block
    if (_mapHeight - _gridMouseY == 0 && _gridMouseX < _mapWidth && _gridMouseX > -1)
    {
        List<int> tempDefaultLayout = new List<int>();
        List<int> tempDefaultOther = new List<int>();

        for (int i = 0; i < _layoutLayer[0].Count; i++)
        {
            tempDefaultLayout.Add(0);
            tempDefaultOther.Add(-1);
        }
        _layoutLayer.Insert(_gridMouseY, tempDefaultLayout);
        _trLayer.Insert(_gridMouseY, tempDefaultOther);
        _entityLayer.Insert(_gridMouseY, tempDefaultOther);
        _logicLayer.Insert(_gridMouseY, tempDefaultOther);
        _mapHeight++;
    }
    else if (_mapWidth - _gridMouseX == 0 && _gridMouseY < _mapHeight && _gridMouseY > -1)
    {
        for (int y = 0; y < _layoutLayer.Count; y++)
        {
            for (int x = 0; x < _layoutLayer[y].Count; x++)
            {
                if (_layoutLayer[y].Count <= _mapWidth)
                {
                    _layoutLayer[y].Add(0);
                    _trLayer[y].Add(-1);
                    _entityLayer[y].Add(-1);
                    _logicLayer[y].Add(-1);
                }
            }
        }
        _mapWidth++;
    }
    return;

The problems:

The first part is about adding tiles to the height (only one row at a time) Adding the temp Lists to the layer Lists with List.Add() doesn't work, I don't know why. I used List.Insert instead.

The second part is used to add a single column to the map one at a time.

Any help would be appreciated.

Answer 1

I actually figured this out:

Using Add() actually works and the problem was in the loop where I was adding the List<int>s to my List<List<int>>s. I was adding the wrong amount (about 430, instead of the 16 I wanted). I couldn't spot this bug earlier because the four hundred-something lists were all empty and didn't render. So Add() was adding the tempList to position 431 or something, and trying to index the layer by [x] at [y] = 16 so it threw an IndexOutOfRangeException. When I fixed the loop there Add() was working as expected.

I also removed the try/catch as it was bad for the exception trace and instead made actual logic that detects clicks outside of the map and Add()s elements to my lists before indexing to place/delete a tile.