new() with reflection on FieldType

Question

I have some code that looks like

else if (oField.FieldType.IsClass)
{
    //var t = oField.FieldType.new()
    someObj.fill_data(t);
    oField.SetValue(o, t);
}

I dont know how to allocate var t. How might i do this? There no way for me to know what the type could be so writing FieldType.IsAssignableFrom(KnownType) can not be a workaround.

Answer 1

Try Activator.CreateInstance:

object t = Activator.CreateInstance(oField.FieldType);

This assumes that type FieldType has a default constructor.

Answer 2

Perhaps you should look into the Type.GetConstructor(...).Invoke(...) of the returned Type.

Answer 3

Here is some example code:

 class TypeTest
 {
     int m_parameter;
     public TypeTest()
     {
     }
     public TypeTest(int parameter)
     {
         m_parameter = parameter;
     }
     public int Param { get { return m_parameter; } }
}

//method1 - Using generic CreateInstance
TypeTest defConstructor = Activator.CreateInstance <TypeTest>();

//method2 - Using GetConstructor
ConstructorInfo c = typeof(TypeTest).GetConstructor(new Type[] { typeof(int)});
TypeTest getConstructor = (TypeTest)c.Invoke(new object[] { 6 });

//method3 - Using non-generic CreateInstance
TypeTest nonDefaultConstructor = (TypeTest)Activator.CreateInstance(typeof(TypeTest), 6);