Query elements of a list inside a dictionary for generic type

I have a dictionary with a key and values as a list with my class StructureData.

private readonly Dictionary<IntBound, List<StructureData>> structuresDataCollection;

We can get RoadStructureData (which inherits StructureData) like this:

public IEnumerable<RoadStructureData> GetRoadDataWithin(IntBound position)
{
    return (IEnumerable<RoadStructureData>)structuresDataCollection.Where(s => s.Key.Intersects(position)).Where(s => s.Value.OfType<RoadStructureData>().Any()).Select(s => s.Value);
}

But I need to write a more generic method to get StructureData for a specified child type for a selected IntBound.

I suppose it could look like this:

public IEnumerable<StructureData> GetDataWithinOfType(IntBound position, Type requiredType)
{
    return structuresDataCollection.Where(s => s.Key.Intersects(position)).Where(s => s.Value.OfType<requiredType>().Any()).Select(s => s.Value);
}

But we can't use a Type variable in the OfType<Type>() method. How to rewrite this code?

Use generics:

public IEnumerable<T> GetRoadDataWithin<T>(IntBound position)
    where T : StructureData
    => structuresDataCollection
        .Where(s => s.Key.Intersects(position))
        .Where(s => s.Value.OfType<T>().Any())
        .Select(s => s.Value.OfType<T>());

The OfType<T> will return an IEnumerable<T>, so you don't need the extra cast (i.e OfType<RoadStructureData> will return an IEnumerable<RoadStructureData>)

usage:

var roadStructureData = GetRoadDataWithin<RoadStructureData>(position);

BTW, note that this code (like the code you wrote) assumes that each list can only have one specific type - so if for instance you have both X and Y types inheriting StructureData, each list can hold only X or only Y, you can't have a list where some items will be X and others Y.