Question

Is it possible to change TEntity to NewEntity after SomeClass has been instantiated?

For example, take this class definition:

public class SomeClass<TEntity> where TEntity : class
{
   public void ChangeSet<NewEntity>()
    {
        TEntity = NewEntity;//not valid
    }
 }

Instantiated for example like this:

var sc = new SomeClass<SomeEntity>();

How can I accomplish this?

sc.ChangeSet<NewEntity>();

Answer 1

Is it possible to change TEntity to NewEntity after SomeClass has been instantiated?

No, this is not possible. How would the CLR know how to map the values from TEntity to SomeEntity? They are different types. It would be like asking your grocer to turn an apple into an orange.

The code below is not recommended. There are so many problems you would have to worry about, and it would be prone to bugs. I am providing it as an example of what you are asking the CLR to do.

SomeClass<Foo> fooClass = new SomeClass<Foo>():
//do stuff to fooClass
SomeClass<Baz> = fooClass.ChangeSet<Baz>();

public class SomeClass<T> where T : class
{
    public SomeClass<K> ChangeSet<K>() where K:class
    {
       var changed = new SomeClass<K>();
       //manually map the properties over
       //but how do you know that Foo.PropertyA fits into Baz.PropetyZed?
       //what happens if Foo.A has a string length of 100, but Baz.A has a max length of 50? What do you do?
       //What id Foo.ID is an INT and Baz.ID is a GUID?
       return changed;
    }
}