Creating generic method

Question

Can someone please help with the following... it's driving me nuts...

// Three methods, virtually identical with the exception of the select field
public IEnumerable<int> GetBrandID()
{
    return myData.Select(m => m.BrandID).Distinct();
}
public IEnumerable<int> GetModelID()
{
    return myData.Select(m => m.ModelID).Distinct();
}
public IEnumerable<int> GetVehicleID()
{
    return myData.Select(m => m.VehicleID).Distinct();
}

// How to create one method which returns the type specified in the parameter??
public IEnumerable<int> GetData(??? myType)
{
    return myData.Select(m => myType).Distinct();
}

One pirate asked another, "Why is that ship wheel sticking out of your pants?"... — Taylor Lopez
– Taylor Lopez, Commented Apr 28, 2016 at 16:52

Jon Skeet · Accepted Answer · 2016-04-28 10:51:44Z

2

It sounds like you probably just want a Func<Model, int> parameter:

public IEnumerable<int> GetData(Func<Model, int> projection)
{
    return myData.Select(projection).Distinct();
}

You could then have:

var modelIds = GetData(m => m.ModelID);
var vehicleIds = GetData(m => m.VehicleID);

Is that what you're after? (That's assuming myData is an IEnumerable<Model>. If it's an IQueryable<Model> you may want to accept Expression<Func<Model, int>> instead.)

answered Apr 28, 2016 at 10:51

Jon Skeet

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1 Comment

X22 Over a year ago

Thanks so much for the assistance, it was clear and straight to the point and helped me immensely. Much appreciated. X22.

Nikola.Lukovic · Accepted Answer · 2016-04-28 11:00:37Z

1

It's not clear what you're exactly after. Maybe something like this?

public static IEnumerable<TResult> GetData<TModel, TResult> (this IEnumerable<TModel> enumerable, Func<TModel, TResult> projection)
{
    return enumerable.Select(projection);
}

And than just call like this:

var ints = myData.GetData<MyModel,int>(m=>m.ModelID).Distinct();
var doubles = myData.GetData<MyModel,double>(m=>m.DoubleProp).Distinct();

etc...

answered Apr 28, 2016 at 11:00

Nikola.Lukovic

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1 Comment

Jon Skeet Over a year ago

Note that if you're providing the data as well, there's no benefit in adding the method - var ints = myData.Select(m => m.ModelID).Distinct()...

drneel · Accepted Answer · 2016-04-28 12:38:37Z

0

public ICollection<T> FindAllWhere(Expression<Func<T, bool>> selectSelector)
{
    ICollection<T> elements = EntitySet.Select(selectSelector).ToList().Distinct();

    return elements;
}

edited Apr 28, 2016 at 12:38

drneel

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answered Apr 28, 2016 at 10:51

Dany

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3 Comments

Jon Skeet Over a year ago

This doesn't appear to answer the question, IMO... it looks like it's an answer to a different question.

Dany Over a year ago

It`s more generic and can change event type of int

Jon Skeet Over a year ago

Well no, at the moment it wouldn't even compile. Let's start with something that answer's the OP's actual requirements, before trying to make it more general than taht.

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