How to split an overridden method into multiple files?

Question

My question is to how to split into multiple files a method containing an override?

I understand that this is not possible with partial.

In my code, I have too much lines in this method. I code on the QuantConnect platform that limits the size of one file, and I reach this limit.

public partial class TestAlgo : QCAlgorithm
{
    public override void OnData(Slice slice) // Name OnData can't be modified.  
    {
    Indices:
        {
            //First Indices
        }

        {
            //Second Indices
        }
        ...
    }
}

Answer 1

Unfortunately, this is not possible. You should refactor your code so that you split your method into multiple methods instead, and then you could use partial, though I'm still not sure why you'd want to do that rather than refactoring complex code into multiple classes.

Answer 2

It says right there in the documentation:

Partial methods are implicitly private, and therefore they cannot be virtual.

More to the point, even with non-virtual methods, partial doesn't allow you to split the method body itself across multiple files. It's just a way of allowing one file to declare the method and another to provide the implementation.

So, we should focus on this part of your question, rather than the XY Problem you've asked about:

I have too much lines in this method. I code on the QuantConnect platform that limits the size of one file, and I reach this limit.

Whatever the limit of the size of the file, I would guess it's a reasonably generous limit. If you've reached that limit as a result of a single method, then you have way too much code in that method.

There are lots of guidelines about how many lines of code a method should have. They are fairly subjective in nature. People debate whether it's "one screen" or "two screens" or something else. But it's safe to say that you've gone way beyond this.

Your method really needs to be refactored into smaller pieces. Probably into smaller classes. How exactly to do that, can't be answered here because you haven't provided that context. But, it needs to be done.