C# Using Reflection With Generic Property

Question

I have a class which uses generic properties. For example:

class Person
{
    public MyGenericProperty<string> Field1
    {
        get { return field1; }
        set { field1 = value; }
    }

    private MyGenericProperty<string> field1= new MyInheritedGenericProperty<string>("Alan1");
}

I want to use this class with reflection at another class and i have a method like that

public void DoSomethingWithProperty(object sourceobject)
{
    foreach (var aProperty in sourceobject.GetType().GetProperties())
    {
        *if(aProperty.PropertyType == typeof(MyGenericProperty<>))*
        {
           *var obj = (MyGenericProperty<>)aProperty.GetValue(sourceobject, null);*
        }
    }
    return null;
}

I have two problem

1- How can do type check of generic property. In that example code of if(aProperty.PropertyType == typeof(MyGenericProperty<>)) does not work.

2- T of MyGenericProperty could be any class and how can cast MyGenericProperty class without knowing T by reflection as

var obj = (MyGenericProperty<>)aProperty.GetValue(sourceobject, null);

Thank for helps.

Answer 1

Firstly, it's important to understand that you don't have a "generic property" - there's no such thing. You have a property whose type is a generic type... and that's not the same thing. (Compare that with a generic type or a generic method, each of which is genuinely generic in terms of introducing new type parameters.)

You can test it using this code:

if (aProperty.PropertyType.IsGenericType &&
    aProperty.GetGenericTypeDefinition() == typeof(MyGenericProperty<>))

But as for the casting - it depends on what you want to do with the value afterwards. You may want to declare a non-generic base type of MyGenericProperty<> containing all the members which don't depend on the type parameter. I'd typically give that the same name as the generic type (eg MyGenericProperty ) just without giving it type parameters. Then if you only need one of those members, you can use:

if (aProperty.PropertyType.IsGenericType &&
    aProperty.GetGenericTypeDefinition() == typeof(MyGenericProperty<>))
{
    var value = (MyGenericProperty) aProperty.GetValue(sourceObject, null);
    // Use value
}

But then in that case you could use Type.IsAssignableFrom anyway:

if (typeof(MyGenericProperty).IsAssignableFrom(aProperty.PropertyType))
{
    var value = (MyGenericProperty) aProperty.GetValue(sourceObject, null);
    // Use value
}

If these hints don't help you, please give more details of what you're trying to do.