4 ms·

Found a few interesting bits there. A reference to a Quiz about C# and object equality: http://blogs.msdn.com/b/jmstall/archive/2005/03/06/386064.aspx http://bl

by ufmace 14y ago

Found a few interesting bits there. A reference to a Quiz about C# and object equality: http://blogs.msdn.com/b/jmstall/archive/2005/03/06/386064.aspx http://blogs.msdn.com/b/jmstall/archive/2005/03/06/386064.as... The last one makes me wonder a bit. Given local int variable x, what does this evaluate to? (object) x.ToString() == (object) x.ToString() When I run it, I get false, and the author says that it's false, because we're doing reference comparison of two independently created objects. But I thought strings were interned in .NET, so if you independently create 2 strings with the same contents, then they are actually the same object, which would make this true?

kvb 14y ago
String constants are interned at compile time. Dynamically created strings are typically not interned.
LoneWolf 14y ago
I would say that it is because each time ToString() is called a new string is created, and at least in the Java I believe that is what will happen, comparison will be false because they are not the same instance.
- ufmace 14y ago
  It's a bit trickier than that due to string interning. That's where there is only one instance framework-wide of a string of a particular value. Try to create a second string with the same value as one you have created already, and you get back a reference to the first string instance. As an example: (object)"XYZ" == (object)"XYZ" returns true. So does: (object) String.Intern(x.ToString()) == (object) String.Intern(x.ToString()) The trick is to know exactly which strings are interned, and when. I initially thought that all strings were, but it seems that string literals in code are always interned, and dynamically-created strings are mostly not interned automatically, but can be manually. http://en.wikipedia.org/wiki/String_interning http://en.wikipedia.org/wiki/String_interning http://msdn.microsoft.com/en-us/library/system.string.intern.aspx http://msdn.microsoft.com/en-us/library/system.string.intern...

by ufmace 14y ago

kvb 14y ago

String constants are interned at compile time. Dynamically created strings are typically not interned.

LoneWolf 14y ago

I would say that it is because each time ToString() is called a new string is created, and at least in the Java I believe that is what will happen, comparison will be false because they are not the same instance.

ufmace 14y ago
It's a bit trickier than that due to string interning. That's where there is only one instance framework-wide of a string of a particular value. Try to create a second string with the same value as one you have created already, and you get back a reference to the first string instance. As an example: (object)"XYZ" == (object)"XYZ" returns true. So does: (object) String.Intern(x.ToString()) == (object) String.Intern(x.ToString()) The trick is to know exactly which strings are interned, and when. I initially thought that all strings were, but it seems that string literals in code are always interned, and dynamically-created strings are mostly not interned automatically, but can be manually. http://en.wikipedia.org/wiki/String_interning http://en.wikipedia.org/wiki/String_interning http://msdn.microsoft.com/en-us/library/system.string.intern.aspx http://msdn.microsoft.com/en-us/library/system.string.intern...