Convert a Type to Reference Type

Question

I have a method that has a constraint like this:

public class MappingTransformation
{
    public static ClassMapped<T> Convert<T>(Mapping<T> source) where T : class
    {
        return ClassMapped<T>.GetInstance(source);
    }
}

This T MUST be reference type because it will be passed to EntityTypeConfiguration.

But, when consuming MappingTransformation.Convert<>(Mapping source) I only have a Type and don't know how to convert this Type into the needed "reference type".

Here is how I'm trying to consume it:

#region Test
        foreach (var item in mappingAssembly.GetTypes())
        {
            var mappingObj = Activator.CreateInstance(item);

            var modelName = mappingObj.GetType().GetProperty("ModelName").GetValue(mappingObj);

            var modelTypeEquivalent = modelAssembly.GetTypes().First(x => x.Name.Equals(modelName));

            var convertido = MappingTransformation.Convert<Model.Clientes>((Mapping<Model.Clientes>)mappingObj);


            var breakpoint = true;
        }
#endregion

How to achieve this?

If i replace with anything, I get a squiggly line underneath it. I don't know what to put there to remove the hardcoded 'Model.Clientes'. — programad, Dec 12 '13 at 18:11

score 2 · Answer 1 · edited May 23 '17 at 11:49

Never answer my own question before, but I think I got it. Still testing, but I think I got it.

Reading some other questions around Stack Overflow, I came to this:

#region Test
        foreach (var item in mappingAssembly.GetTypes())
        {
            var mappingObj = Activator.CreateInstance(item);

            var modelName = mappingObj.GetType().GetProperty("ModelName").GetValue(mappingObj);

            var modelTypeEquivalent = modelAssembly.GetTypes().First(x => x.Name.Equals(modelName));

            var convertionMethod = typeof(MappingTransformation).GetMethod("Convert");
            var genericConvertionMethod = convertionMethod.MakeGenericMethod(modelTypeEquivalent);
            var result = genericConvertionMethod.Invoke(null, new object[] { mappingObj });

            var breakpoint = true;
        }
#endregion

This was the question that lead me to the answer from Mr. Jon Skeet.

score 0 · Answer 2 · edited May 23 '17 at 12:03

0

I think I understand.

It looks like you want to define the type of your generic function at runtime, something like this?

        var modelTypeEquivalent = modelAssembly.GetTypes().First(x => x.Name.Equals(modelName));

        var convertido = MappingTransformation.Convert<modelTypeEquivalent >((Mapping<Model.Clientes>)mappingObj);

You want to find the type and then pass it as the type for your generic, is that right?

That's actually trickier than you might think. Types applied to generic functions and classes must be defined at compile time, not run time.

To do what you want, you'll need to use more reflection, see this related question for an example.

edited May 23 '17 at 12:03

Community

1
1

answered Dec 12 '13 at 18:28

SouthShoreAK

4,176
2
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48

Yes, that is the problem. Pass the type to the generics brackets. On the related question you posted, they managed to get to work with var count = x.CountItems((IStorable)someObjectThatImplementsStorable); witch is the exact same situation. But mine isn't "IStorable", it is another generic method! (Mapping). Thats the catch I can't figure out. – programad Dec 12 '13 at 18:34

Convert a Type to Reference Type

2 Answers2