asp.net - make generic method to find if entity exists in db

Question

I have a problem with rewriting part of my code to generic function which would be used in other methods.

this is example of code i want to rewrite:

if(!await _bikeDbContext.Order.AnyAsync(x => x.OrderId == orderId))
      {
        throw new BusinessNotFoundException("Order was not found");
      }

and this is something i'd like to have:

await _bikeDbContext.Order.IsAnyRule(x => x.OrderId == orderId));

I started writing code on my own but I have no clue what to put in function's body

public static void IsAnyRule<TEntity>(TEntity entity)
      where TEntity : class
    {
      
    }

If you want the usage as described, you'll need an extension method on DbSet<TEntity> — Fildor
– Fildor, Commented Sep 21, 2021 at 14:26
The methods you use are already generic. DbSet<T>.Find is already generic. .Any(...) is already generic. Why do you want something else? What actual problem are you trying to solve? — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Sep 22, 2021 at 7:36
Why make an existence check instead of writing code that works whether the entity exists or not? Eg .FirstOrAsync will load the entity or return null if it's missing. — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Sep 22, 2021 at 7:42

huMpty duMpty · Accepted Answer · 2021-09-22 07:34:34Z

1

 public bool IsExist<TEntity>(Expression<Func<TEntity, bool>> predicate = null) where TEntity : class
        {
            IQueryable<TEntity> data = _bikeDbContext.Set<TEntity>();
            return data.Any(predicate);
        }

then use as

IsExist<Order>(x => x.OrderId == orderId);

edited Sep 22, 2021 at 7:34

answered Sep 21, 2021 at 15:23

huMpty duMpty

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2 Comments

Richard Deeming Over a year ago

Probably better to use .Any(predicate) instead of .FirstOrDefault(predicate) != null, since FirstOrDefault will load the entity into the change tracker, which will change the behaviour of the code.

Panagiotis Kanavos Over a year ago

@huMptyduMpty this answerr is essentially just IQueryable<T>.Any(). It's not wrong. It's the question that makes little sense. IQueryable and DbSet methods are already generic

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