@Sergio23 , based on my test, I reproduced the same error with you.
Please change the following code in the Example.cs.
Change
ResourceManager rm = new ResourceManager("Example.Greeting",
typeof(Example).Assembly);
To
ResourceManager rm = new ResourceManager("Greeting", typeof(Example).Assembly);
Also, it is mentioned in the Microsoft doc:
After you changed the above code and compile the app again, you can see the following result.
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