I have in my model a property of a certain type, it's a custom object.
This object takes a string as a ctor argument.
Is it possible to have the model binder automatic insert a string from a form into the ctor of the particular object ?
yes it is. With a custom model binder, you can explicitly control exactly how values are used to construct your object. This can include route values, form posted values as well as values from the session store.