Why string interned but has different references?

Question

string s1 = "abc";
string s2 = "ab";
string s3 = s2 + "c";

Console.WriteLine(string.IsInterned(s3));           // abc
Console.WriteLine(String.ReferenceEquals(s1, s3));  // False

I just cannot understand why s3 interned, but ReferenceEquals was False.

Dose they have two copies in intern pool?

Thanks in advance.

Answer 1

They are separate references. The string "abc" is interned because it is a literal string.

The expression s2 + "c" is compiled to string.Concat(s2, "c").. which results in a new (and separate) string reference.