methods that are returning different return types

Question

I have below methods and they are returning different entities in addition to that the input parameters going to these methods all are same and I am using those ones in where condition

   public IQueryable<LibraryEnvironment> EnvironmentFields(string spaceFunction, string category, string source)
    {
        return _dbContext.LibraryEnvironment.Where(s => s.SpaceFunction == spaceFunction
                                                                && s.Category == category &&
                                                                 s.EnvironmentSource.Name == source);
    }

    public IQueryable<LibraryEquipment> EquipmentFileds(string spaceFunction, string category, string source)
    {
        return _dbContext.LibraryEquipment.Where(s => s.SpaceFunction == spaceFunction
                                                              && s.Category == category &&
                                                               s.EquipmentSource.Name == source);
    }

    public IQueryable<LibraryLighting> LightingFields(string spaceFunction, string category, string source)
    {
        return _dbContext.LibraryLighting.Where(s => s.SpaceFunction == spaceFunction
                                                             && s.Category == category &&
                                                              s.LightingSource.Name == source);
    }

there are other methods similar to this kind as well

I am looking for a way to create the common generic method among all these methods but with a different return type and could not be able to figure it out the way. I am using .Net core with EF core

if anyone suggest any ideas on this that would be very grateful to me, thanks in advance

Answer 1

You can use the Set<T> method on DbContext to generically access sets. If you put all the relevant properties your filtering on into a base you can then constrain the generic parameter to that base type and still filter on all your properties.

So your classes would look something like this based on your original queries:

public class Entity
{
    public string SpaceFunction { get; set; }
    public string Category { get; set; }
}

public class LightingEquipment : Entity
{
    public LightingSource LightingSource { get; set; }
}

public class LightingSource
{
    public string Name { get; set; }
}

And your method would like this, using a source selector:

public IQueryable<T> Fields<T>(string spaceFunction, string category, string source, Func<T, string> sourceSelector) where T : Entity
{
    return _dbContext.Set<T>().Where(s => s.SpaceFunction == spaceFunction
                              && s.Category == category &&
                              sourceSelector(s) == source);
}

And you would call this method like this:

public void Consumer()
{
    var queryable = Fields<LightingEquipment>("spaceFunction", "category", "source", x => x.LightingSource.Name);
}

Docs for Set<T>()