convert object to type generic - automapper static extension

Question

I'm trying to convert my AutoMapper code to be more fluent-api like, e.g. existing code:

Model.Foo target = Mapper.Map<Contract.Foo, Model.Foo>(source);

What I'd like the code to look like is this

Model.Foo target = source.ConvertTo<Model.Foo>();

I started writing my extension method, but I can't seem to get this to work.

public static class AutoMapperConverterExtension
{
    public static T ConvertTo<T>(this string source) where T : new()
    {
        Type sourceType = Type.GetType(source); 
        if (IsMapExists<sourceType, T>()) // complains here! cannot resolve 'sourceType'. If I use inline, won't compile.
        {
            return Mapper.Map<T>(source);    
        }
        throw new NotImplementedException("type not supported for conversion");
    }

    public static bool IsMapExists<TSource, TDestination>()
    {
        return (AutoMapper.Mapper.FindTypeMapFor<TSource, TDestination>() != null);
    }        
}

And what problems are you having with your implementation? – Servy Sep 22 '14 at 18:57 — Servy, Sep 22 '14 at 18:57
*complains here* about what? – Yuval Itzchakov Sep 22 '14 at 18:59 — Yuval Itzchakov, Sep 22 '14 at 18:59
updated the post -- basically, won't compile. – Raymond Sep 22 '14 at 19:19 — Raymond, Sep 22 '14 at 19:19

score 4 · Accepted Answer · answered Sep 22 '14 at 19:24

It looks like you are over-complicating things, and you might be able to get away with:

public static T ConvertTo<T>(this object source)
{
    return Mapper.Map<T>(source);
}

That said, you can't use generics as you are attempting to do in the code code as posted. sourceType is a runtime variable, and cannot be used for a generic type argument, which is determined at compile time. In this particular case, AutoMapper provides a non-generic version of FindTypeMapFor() that you can use.

You also cannot assume that source is going to be a string parameter. You probably want an object.

public static T ConvertTo<T>(this object source) where T : new()
{
    Type sourceType = Type.GetType(source); 
    if (IsMapExists(sourceType, typeof(T)))
    {
        return Mapper.Map<T>(source);
    }
    throw new NotImplementedException("type not supported for conversion");
}

public static bool IsMapExists(Type source, Type destination)
{
    return (AutoMapper.Mapper.FindTypeMapFor(source, destination) != null);
}

score 2 · Answer 2 · edited May 23 '17 at 11:52

2

The line throwing the error needs to change to use reflection when calling the generic function.

var method = typeof(AutoMapperConverterExtension).GetMethod("IsMapExists");
var generic = method.MakeGenericMethod(sourceType, typeof(T));

bool exists = Convert.ToBoolean(generic.Invoke(null, null));

if (exists) 
{
    return Mapper.Map<T>(source);    
}

How do I use reflection to call a generic method?

edited May 23 '17 at 11:52

Community

1
1

answered Sep 22 '14 at 19:31

Ismail Hawayel

2,167
18
16

thank you, I learned something new, but I marked the other answer as correct as it better solves the problem I was facing. – Raymond Sep 22 '14 at 21:40

convert object to type generic - automapper static extension

2 Answers2