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  1. using System;
  2.  
  3. public class Test
  4. {
  5.     public static void Main()
  6.     {
  7.     	new Child1();
  8.     	new Child2();
  9.     }
  10. }
  11.  
  12. class Parent
  13. {
  14.     public Parent() { DoSomething(); }
  15.     protected virtual void DoSomething() {}
  16. }
  17.  
  18. class Child1 : Parent
  19. {
  20.     private string foo = "FOO";
  21.     protected override void DoSomething() => Console.WriteLine(foo.ToLower());
  22. }
  23.  
  24. class Child2 : Parent
  25. {
  26.     private string foo;
  27.     public Child2() { foo = "FOO"; }
  28.     protected override void DoSomething() => Console.WriteLine(foo.ToLower());
  29. }
Runtime error #stdin #stdout #stderr 0.01s 134976KB
comments (?)
stdin
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Standard input is empty
stdout
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foo
stderr
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Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
  at Child2.DoSomething () [0x00000] in <302b0a83289e4df688d6c9a0429c0c48>:0 
  at Parent..ctor () [0x00006] in <302b0a83289e4df688d6c9a0429c0c48>:0 
  at Child2..ctor () [0x00000] in <302b0a83289e4df688d6c9a0429c0c48>:0 
  at Test.Main () [0x00006] in <302b0a83289e4df688d6c9a0429c0c48>:0 
[ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
  at Child2.DoSomething () [0x00000] in <302b0a83289e4df688d6c9a0429c0c48>:0 
  at Parent..ctor () [0x00006] in <302b0a83289e4df688d6c9a0429c0c48>:0 
  at Child2..ctor () [0x00000] in <302b0a83289e4df688d6c9a0429c0c48>:0 
  at Test.Main () [0x00006] in <302b0a83289e4df688d6c9a0429c0c48>:0
https://ideone.com/jqBKl7
language:
C# (gmcs 5.20.1)
created:
6 years ago
visibility:
public

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