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  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4.  
  5. public class Test
  6. {
  7. 	public static void Main()
  8. 	{
  9. 	    var foo = new Foo();
  10. 	    foo.GetFoo1().Add("hello! why can I do this??");
  11. 	    Console.WriteLine(string.Join(", ", foo.GetFoo1()));
  12.  
  13. 	    foo.GetFoo2().Add("this won't change the field");
  14. 	    Console.WriteLine(string.Join(", ", foo.GetFoo2()));
  15.  
  16. 	    // Won't compile:
  17. 	    // foo.GetFoo3().Add("??");
  18.  
  19. 	    ((IList<string>) foo.GetFoo3()).Add("This works, but people are unlikely to make this mistake");
  20. 	    Console.WriteLine(string.Join(", ", foo.GetFoo3().ToList()));
  21. 	}
  22.  
  23. 	class Foo
  24. 	{
  25. 	    private readonly List<string> foo = new List<string>();
  26.  
  27. 	    public List<string> GetFoo1()
  28. 	    {
  29. 	        return this.foo;
  30. 	    }
  31.  
  32. 	    public List<string> GetFoo2()
  33. 	    {
  34. 	        return this.foo.ToList();
  35. 	    }
  36.  
  37. 	    public IEnumerable<string> GetFoo3()
  38. 	    {
  39. 	        return this.foo;
  40. 	    }
  41. 	}
  42. }
Success #stdin #stdout 0.03s 24184KB
comments (?)
stdin
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Standard input is empty
stdout
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hello! why can I do this??
hello! why can I do this??
hello! why can I do this??, This works, but people are unlikely to make this mistake
https://ideone.com/KQOKa3
language:
C# (gmcs 5.20.1)
created:
10 years ago
visibility:
public

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