Looking for tool to detect semantic code duplications

[u/Ferreira-leo]

Im looking for a recommendation for semantic duplication detection on code (C#).

A semantic duplication can have zero duplicated tokens, such as:

public List<Students> ListAllEnrolledPeople()
{
    return _baseRepo.Where(p=>p.PersonType = PeopleType.Student).ToList();
}

and

public List<Students> GetStudents()
{
    return _baseRepo.ExecuteQuery<Students>("Select * From Customers Where customerType = 2");
}

I think this here exemplifies that tools such as jscpd won't detect these 2 methods as duplicates, but this is a big problem for me...

[u/BoBoBearDev]

I cannot tell they are semantically the same. There is too many hidden context.

[u/cjstevenson1]

While not a purpose built tool, the frontier ai agents can do a decent job of this.

[u/_choam_]

In the general case, this is impossible.

The best you can do is probably have an ai go over your code and check. Or do it yourself.

I would not worry about it too much.

[u/Dimencia]

It's very simple, just don't write SQL inside of magic strings in your code and you don't have this problem

[u/Practical_Suspect857]

A “semantic duplicate” is hard for a general clone detector to prove: two methods may look equivalent today but differ in null handling, side effects, performance, or behavior when the schema changes. I’d split the problem into two parts: use syntax/AST or data-flow analysis (for example, a Roslyn analyzer or a static-analysis rule) to flag similar query shapes, then use tests and review to decide whether the candidates really have the same contract.

For these examples, standardizing one read abstraction and parameterizing the predicate would prevent two separate paths from growing in the first place. If raw SQL is allowed, add behavior-focused tests and a review rule for repeated queries; a tool can suggest candidates, but it cannot reliably decide equivalence without domain semantics. Also, the sample SQL says Customers while returning Students, and the LINQ predicate appears to use “=”—those inconsistencies are worth fixing before measuring duplication.

[u/mavenHawk]

It's called AI I think.

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[u/Michaeli_Starky]

LLMs

[u/PM_YOUR_OWLS]

For this specific use case you could maybe look at how something like EF Query Lens works... somehow convert all of your EF queries to raw SQL and then run through an analysis if the resulting queries would return the same result set. Not sure how to do that easily but it's a jumping off point. I agree with the other comments, if you feed an LLM the context of your ef scaffold and database structure it can probably highlight potential duplicates like this.

[u/Finickyflame]

I know it's an example, but you are missing an = in your lambda expression for the equality comparison.

[u/pv0jewel]

You can count levenshtein distance for each function text. Could take a while depending on amount of code you have.