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c#genericstypesinference
h.alex
h.alex

Reputation: 902

Type inference in lambdas

I have this functionality:

 public class Repository : IRepository
    {
        public List<TEntity> GetOrdered<TEntity, TSortKey>(Func<TEntity, TSortKey> orderBy, int take, params string[] includePaths) where TEntity : AbstractEntity
        {
            var query = (from ent in this.Context.Set<TEntity>() select ent).IncludePaths(includePaths);

            return query.OrderBy(orderBy).Take(take).ToList();
        }
    }

To invoke it:

List<Project> p = repository.GetOrdered<Project, string>(x => x.Name, 10);

I want to eliminate the need to give it the second generic parameter when invoking, it's a deal breaker from an API perspective.

How to do it?

Upvotes: 1

Views: 89

Answers (2)

D Stanley
D Stanley

Reputation: 152521

it's a deal breaker from an API perspective

then consider your deal broken... You can't partially infer generic parameters. If your repository was generic you could possibly do:

 public class Repository<TEntity> : IRepository<TEntity> where TEntity : AbstractEntity
{
    public List<TEntity> GetOrdered<TSortKey>(Func<TEntity, TSortKey> orderBy, int take, params string[] includePaths) 
    {
        var query = (from ent in this.Context.Set<TEntity>() select ent).IncludePaths(includePaths);

        return query.OrderBy(orderBy).Take(take).ToList();
    }
}

then do

List<Project> p = repository.GetOrdered(x => x.Name, 10);

But I don't know if that change is possible for you.

Upvotes: 3

Mathias Becher
Mathias Becher

Reputation: 703

Either the compiler can infer all type parameters, or you have to specify them all. But you may explicitly specify the argument type of the lambda expression, such as:

List<Project> p = repository.GetOrdered((Project x) => x.Name, 10);

Upvotes: 1

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